extraterrestrial he in sediments: from recorder of...

Extraterrestrial He in Sediments:From Recorder of Asteroid Collisionsto Timekeeper of Global EnvironmentalChanges

David McGee and Sujoy Mukhopadhyay

Abstract

Most 3He in deep-sea sediments is derived from fine-grained extraterres-trial matter known as interplanetary dust particles (IDPs). These particles,typically\50 lm in diameter, are sufficiently small to retain solar wind-implanted He with high 3He/4He ratios during atmospheric entry heating.This extraterrestrial 3He (3HeET) is retained in sediments for geologicallylong durations, having been detected in sedimentary rocks as old as480 Ma. As a tracer of fine-grained extraterrestrial material, 3HeET offersunique insights into solar system events associated with increased IDPfluxes, including asteroid break-up events and comet showers. Studies haveused 3HeET to identify IDP flux changes associated with a Miocene asteroidbreak-up event and a likely comet shower in the Eocene. During much ofthe Cenozoic, 3HeET fluxes have remained relatively constant over million-year timescales, enabling 3HeET to be used as a constant flux proxy forcalculating sedimentary mass accumulation rates and constraining sedi-mentary age models. We review studies employing 3HeET-based accumu-lation rates to estimate the duration of carbonate dissolution eventsassociated with the K/Pg boundary and Paleocene-Eocene ThermalMaximum. Additionally, 3HeET has been used to quantify sub-orbitalvariability in fluxes of paleoproductivity proxies and windblown dust.In order to better interpret existing records and guide the application of3HeET in novel settings, future work requires constraining the carrierphase(s) of 3HeET responsible for long-term retention in sediments,better characterizing the He isotopic composition of the terrigenous

D. McGee (&)Department of Earth, Atmospheric and PlanetarySciences, Massachusetts Institute of Technology,Cambridge, MA, USAe-mail: [email protected]

S. MukhopadhyayDepartment of Earth and Planetary Sciences,Harvard University, Cambridge, MA, USAe-mail: [email protected]

P. Burnard (ed.), The Noble Gases as Geochemical Tracers, Advances in Isotope Geochemistry,DOI: 10.1007/978-3-642-28836-4_7, � Springer-Verlag Berlin Heidelberg 2013

155

end-member, and understanding why observed extraterrestrial 3He fluxesdo not match the predicted variability of IDP accretion rate over orbitaltimescales.

1 Introduction

The presence of extraterrestrial material in mar-ine sediments was first proposed by Murray(1876) based upon his observations of magneticspherules in open-ocean surface sedimentscollected during the Challenger expedition. Laterinvestigations found similar spherules at highaltitudes in the atmosphere and in ice sheets,terrestrial deposits and geologically old marinesediments (Laevastu and Mellis 1955; Firemanand Kistner 1961; Thiel and Schmidt 1961;Fredriksson and Gowdy 1963). Geochemical andmineralogical investigations of cut and polishedsamples provided evidence consistent with anextraterrestrial origin for at least some of thesespherules, including metallic iron cores and highnickel contents (Fredriksson 1956; Fredrikssonand Martin 1963). In parallel with this work,studies of meteorites established that extrater-restrial materials contained noble gas signaturesclearly distinguishable from terrestrial samples,marked most notably by high 3He concentrationsand 3He/4He ratios (e.g., Tilles 1962; Zähringer1962). Drawing upon these findings, Merrihue(1964) demonstrated that the He isotopic com-position of a red clay sample from the southtropical Pacific was inconsistent with any knownterrestrial source and was similar to that found inextraterrestrial samples.

Subsequent work has established that most3He in open-ocean sediments is extraterrestrial,and that this extraterrestrial 3He (3HeET) isdominantly brought to Earth’s surface by fine(generally\50 lm) interplanetary dust particles(IDPs). IDPs consist of a combination of aster-oid and comet debris and carry implanted solarions with characteristically high 3He/4He ratios.Though all extraterrestrial matter initially con-tains implanted He, coarser particles attainhigher temperatures during atmospheric entry,causing them to lose most of their 3HeET before

reaching the Earth’s surface. The atmospherethus acts as a filter, allowing only fine particlesto retain 3HeET.

Over the past 30 years 3HeET has beenidentified in Quaternary marine sediments (e.g.,Takayanagi and Ozima 1987; Farley andPatterson 1995; Marcantonio et al. 1995) and icecores (Brook et al. 2000); in marine sedimentsspanning the Cenozoic (Farley 1995); and insedimentary rocks as old as 480 Ma (Pattersonet al. 1998). When combined with sedimentaryaccumulation rate estimates, 3HeET data provideinsight into past changes in the flux of extra-terrestrial material associated with asteroidbreak-up events and comet showers (Farley1995; Farley et al. 1998, 2005, 2006;Mukhopadhyay et al. 2001a, b). Because 3HeET

traces the accretion of IDPs dominantly smallerthan 50 lm, 3HeET fluxes offer a view ofaccretion rates of extraterrestrial matter that isdistinct from that provided by platinum groupelements (PGEs) such as iridium, which tracethe total extraterrestrial mass flux; large impac-tors leave PGE anomalies in the sedimentaryrecord but contribute negligible amounts of3HeET (e.g., Mukhopadhyay et al. 2001a, b).Likewise, collisions in the asteroid belt sub-stantially enhance IDP accretion rates—andthus, 3HeET fluxes—without delivering largeimpactors (Farley et al. 2006).

As 3HeET accumulation rates have been foundto be roughly constant on million-year timescalesthrough most of the Cenozoic, 3HeET can also beused as a constant-flux proxy for calculatingsedimentary accumulation rates (Marcantonioet al. 1995, 1996; Mukhopadhyay et al. 2001b,Farley and Eltgroth 2003). This approach hasproved particularly valuable in portions of thesedimentary record marked by dramatic changesin sedimentation (e.g., Mukhopadhyay et al.2001b; Farley and Eltgroth 2003; Murphy et al.2010). Even in periods of more typical pelagicsedimentation, 3HeET-based accumulation rates

156 D. McGee and S. Mukhopadhyay

allow calculation of fluxes for paleoclimatestudies with sub-orbital resolution that are largelyindependent of age model errors, changes in car-bonate preservation and lateral advection of sed-iments (Winckler et al. 2005; Marcantonio et al.2009; McGee et al. 2010; Torfstein et al. 2010).

In this chapter we review the current under-standing of the sources of IDPs and the carrierphases of extraterrestrial He responsible forlong-term retention of He in marine and terres-trial deposits. We then discuss applications of3HeET to questions of past changes in IDP fluxand marine sediment accumulation. We closethe chapter with a set of open questions thatprovide directions for future work.

2 Origin of ExtraterrestrialHe in IDPs

Interplanetary dust particles originate as asteroidand comet debris and range in size from *1 lmto 1 mm, with a peak in mass flux near Earth at adiameter of *200 lm (Love and Brownlee1993). IDPs are typically porous aggregates ofsilicate minerals and carbonaceous matter (Nierand Schlutter 1990), with densities averaging*2 g/cm3 and ranging from 1 to 6 g/cm3 (Loveet al. 1994). Poynting-Robertson and solar winddrag cause IDP orbits to decay toward the Sun ontimescales of 104–105 years (Burns et al. 1979).This short lifetime requires continuous supply ofnew IDPs to the inner solar system. IDP sourcesinclude asteroid collisions and comets, though therelative importance of these sources is as yetuncertain. Kortenkamp and Dermott (1998b)argued that much of the zodiacal cloud, the diffusecloud of dust in the plane of the solar system,originates from collisions of a limited number ofasteroid families. More recently, modeling byNesvorny et al. (2010) suggested that Jupiter-family comets might be the most important sourceof IDPs at distances closer than 5 AU.

As IDPs spiral into the sun they are bombardedby solar wind (SW), which imparts high noble gasconcentrations and solar isotopic ratios. SW ionsare primarily composed of H and He with particleenergies on the order of 1 keV/n (Futagami et al.

1990) and 3He/4He ratios of 4.48 (±0.15) 9 10-4

(Benkert et al. 1993). 3He/4He ratios in IDPssampled in the stratosphere reach the solar windvalue of 4.4 9 10-4, although the majority of theparticles have ratios *2.0–2.7 9 10-4 (Fig. 1)(Nier and Schlutter 1990, 1992; Pepin et al.2000). The lower-than-SW 3He/4He ratios inmost IDPs have led to suggestions that SW He islost during atmospheric entry and that IDP Heinstead reflects a distinct population of higherenergy solar ions with lower 3He/4He ratios,called solar energetic particles (SEP; Amari andOzima 1988; Nier et al. 1990; Pepin et al. 2000).However, study of solar ions implanted during theGenesis mission has recently demonstrated thatthe heavier isotope is implanted deeper, resultingin depth-dependent isotopic fractionation suchthat lighter compositions are observed near thesurface (Grimberg et al. 2006; Wieler et al. 2007).If so, the lower 3He/4He ratios observed in IDPsmight simply indicate preferential loss of the

Strato

spher

ic ID

Ps

Clust

er ID

Ps

50-4

00 µ

m A

ntarc

tic ID

Ps

Antarc

tic ic

e

10-4

10-3

10-2

10-1

3H

e/4H

e

Solar wind

Fig. 1 3He/4He ratios of IDPs collected from thestratosphere and from Antarctic ice. Dashed line indi-cates the 3He/4He ratio of solar wind (4.48 9 10-4).Note that most IDPs have 3He/4He ratios similar to orlower than solar wind, while cluster IDPs (fragments oflarge IDPs) commonly have much higher 3He/4He ratios,perhaps due to spallogenic He production by galacticcosmic rays. Stratospheric IDPs: Nier et al. (1990), Nierand Schlutter (1992). Cluster IDPs: Nier and Schlutter(1993). 50–400 lm Antarctic IDPs: Stuart et al. (1999).Antarctic ice: Brook et al. (2000)

Extraterrestrial He in Sediments 157

more shallowly implanted component of solarwind ions during atmospheric entry heating ratherthan a separate SEP component.

Though most data support a solar source of Hein IDPs, some fragments of cluster IDPs col-lected in the stratosphere—large (*40 lm) IDPsthat break up when impacting the collector sur-face—have 3He/4He ratios of up to *1 9 10-2

(Fig. 1) (Nier and Schlutter 1993; Pepin et al.2000, 2001). Spallation reactions from galacticcosmic rays (GCR) or solar cosmic rays (SCR)appear to be the only plausible source of these3He/4He ratios. In some cases, 3He/4He ratios indeep-sea ferromanganese crusts also indicate thepresence of GCR-produced 3He (Basu et al.2006). However, the 3He flux implied from fer-romanganese crusts is a few orders of magnitudelower than that inferred from marine sediments.Furthermore, in magnetic separates from deepsea sediments the measured Ne isotopic compo-sitions appear to be primarily a two componentmixture of SW and atmospheric Ne (Fukumotoet al. 1986; Matsuda et al. 1990). Thus, GCR- orSCR-produced 3He appears not to be a majorcomponent of the extraterrestrial 3He inventory.

3 IDPs in Terrestrial Deposits

3.1 Determinationof Extraterrestrial Noble Gases

In marine sediments and ice cores He is often atwo component mixture of extraterrestrial Hefrom IDPs and terrigenous He present in detritalminerals (Fig. 2a). The concentration of extra-terrestrial 3He can be estimated using the fol-lowing equation (Marcantonio et al. 1995):

3HeET

� �¼

1�3He=4HeTERR3He=4Hemeas

1� 3He=4HeTERR3He=4HeIDP

0

@

1

A � 3Hemeas

� �ð1Þ

where brackets indicate concentrations, ‘meas’indicates the measured values, and 3He/4HeTERR

and 3He/4HeIDP denote the ratios for the terrig-enous and extraterrestrial endmembers,respectively.

The fraction of 3HeET in the sediments isusually insensitive to the choice of whether theIDP 3He/4He ratio is 4.48 9 10-4 (SW value;Benkert et al. 1993) or the average value of2.4 9 10-4 observed in stratospheric IDPs (Nierand Schlutter 1990; 1992). The 3He/4HeTERR

ratio typically varies between 2–4 9 10-8 butoccasionally may reach 10-7. When the mea-sured 3He/4He ratios in the sediments are in the10-5 range, the deconvolution is insensitive tothe choice of the terrigenous endmember(Fig. 2b; Marcantonio et al. 1995; Farley andPatterson 1995; Mukhopadhyay et al. 2001a;Higgins et al. 2002; Winckler et al. 2005).However, when measured ratios are in the low10-6 to 10-7 range, such as in continental marginsediments and other settings with high silici-clastic inputs, studies must consider the sensi-tivity of 3HeET concentrations to uncertainties inthe 3He/4HeTERR ratio (e.g., McGee et al. 2010).

The 3He/4HeTERR ratio is usually governed bythe coupled production of 4He from U and Thdecay and 3He from the reaction 6Li(n,a)3H?3He,where the source of the neutrons is the decay of Uand Th (Andrews 1985; Mamyrin and Tolstikhin1984). The 3He/4He production ratio in crustalmaterials is B4 9 10-8 (Andrews 1985; Mamyrinand Tolstikhin 1984), four orders of magnitudelower than 3He/4HeET. This value is similarto values measured for bulk Chinese loess(Marcantonio et al. 1998; Farley 2000; Du et al.2007; McGee 2010). Some terrigenous samples,however, have 3He/4He ratios of *10-7, a factorof 10 higher than the average production rate forthe upper continental crust (Marcantonio et al.1998). Recent work has demonstrated that the finefraction of Chinese loess (\4 lm) has a factor of10 higher 3He/4He ratios (*10-7) than bulk loess,suggesting that the grain size of terrigenous inputsshould be taken into account in choosing3He/4HeTERR (McGee 2010).

A systematic understanding of what controlsterrigenous 3He/4He ratios would help in deter-mining 3He/4HeTERR for various settings, but atpresent, the source of high (C10-7) 3He/4Heratios in terrigenous sediments is debated.Air-derived 3He appears to be ruled out in sedi-ments even when the measured 3He/4He ratios are


close to atmospheric (1.4 9 10-6). Measure-ments of Ne concentrations in sediments multi-plied by the He/Ne ratio of air indicate that insediments at DSDP Site 607 (Farley andPatterson 1995), LL44-GPC3 (Farley 2000), and

Gubbio in the Italian Apennines (Mukhopadhyayet al. 2001a) the percentage of air-derived 3He isB1 %. On the other hand, mantle He has beensuggested as an important contributor (Marcan-tonio et al. 1998; Tolstikhin and Drubetskoy

10-14 10-13 10-12 10-11 10-10 10-9

3He (cc STP/g non-carbonate)

10-8

10-7

10-6

10-5

10-4

3H

e/4H

e

Eq. Pacific (Late Pleistocene)

N. Atlantic (Late Pleistocene)

N. Pacific (Pleistocene)N. Pacific (Cretaceous-Pliocene)

Eq. Atlantic (Late Miocene)

Italian Apennines (Cretaceous-Eocene)

Chinese loess

IDP He

Terr. He

10-8 10-7 10-6 10-5 10-4

3 He/ 4He

0

20

40

60

80

100

Per

cen

t ex

trat

erre

stri

al3H

e

N. Atlantic Apennines

Eq. Pacific

(a)

(b)

Fig. 2 Mixing between extraterrestrial and terrigenousHe in terrestrial sediments. a He isotope data from depositsspanning from the late Cretaceous to the Holocene (afterMarcantonio et al. 1998). Lines depict mixing betweenIDP He (3He/4He = 2.4 9 10-4) and two hypotheticalterrigenous endmembers. Chinese loess data are shown asa potential terrigenous endmember for North Pacificsediments. 3He concentrations are calculated for the non-carbonate fraction of sediments. Even in IDP-rich sam-ples, sedimentary 3He/4He ratios typically do not exceed2.4 9 10-4. b Plot showing the fraction of 3He that is

extraterrestrial for different measured 3He/4He ratios (afterFarley 2000). Lines indicate terrigenous endmembers with3He/4He ratios of 10-7 and 10-8; most studies assume3He/4He ratios of 2–4 9 10-8 for the terrigenous end-member. Ranges of measured 3He/4He ratios fromselected studies are shown for reference. EquatorialPacific: Marcantonio et al. (1995); North Pacific: Farley(1995). North Atlantic: McGee et al. (2010). EquatorialAtlantic: Farley et al. (2006). Italian Apennines: Mukho-padhyay et al. (2001a). Chinese loess: Marcantonio et al.(1998), Farley (2000)


1975) with some volcanic rocks having 3He/4Heratios on the order of 10-5. Cosmogenic Heproduced within minerals such as olivines andpyroxene can also have high 3He/4He ratios.Based on in-vacuo crushing of mantle minerals(e.g., Kurz et al. 1996), Farley (2000) argued thatmost mantle He (*90 %) would be lost by thetime the volcanic material is ground down tograin sizes of a few to few 10 s of microns fortransport to the ocean. Additionally, while theglobally averaged cosmogenic 3He production issimilar to the flux of 3HeET, Farley (2000) arguedthat cosmogenic He inventory in sediments mustbe low, since most terrigenous materials areactually derived from a very small percentage ofthe Earth’s surface, and the most common ter-rigenous minerals (quartz, feldspars, clays) havevery low He retentivity. An additional possibilityfor relatively high 3He/4He ratios in crustalmaterial is that terrigenous 3He and 4He may beheld in separate phases that respond differently toweathering, leading some deposits to have ele-vated 3He/4He ratios due to preferential loss ofradiogenic 4He (Tolstikhin et al. 1996).

One key uncertainty in determining the correct3He/4HeTERR for the deconvolution (Eq. 1) is thepossibility that samples taken to represent theterrigenous endmember contain IDPs. To theextent that IDPs retain 3HeET during weatheringand transport, 3He/4He ratios in fan sedimentsand loess deposits—sediments often taken toreflect the terrigenous endmember—may behigher than the true 3He/4HeTERR due to thepresence of IDPs. As an example, Marcantonioet al. (1998) found relatively high 3He/4He ratiosin Amazon fan sediments (*1–2 9 10-7). Theserapidly accumulating sediments should have lowconcentrations of directly in-falling IDPs. It is notknown whether the high ratios reflect terrigenoussources (possibly enriched in mantle He) (Mar-cantonio et al. 1998) or additions of IDPsdeposited in the Amazon watershed and trans-ported to the fan (Farley 2000). Likewise, theobservation that the fine fraction of Chinese loesshas higher 3He/4He ratios than bulk loess (McGee2010) could result from the fact that IDPs wouldbe concentrated in the fine fraction.

In cases where 3HeET values are sensitive to3He/4HeTERR and in which 3He/4HeTERR is notknown, three approaches have been taken toestimate 3He/4HeTERR. The first and most basicapproach is to take the lowest 3He/4He value inthe dataset as an upper bound on 3He/4HeTERR

(McGee et al. 2010). Second, as IDPs are con-centrated in the magnetic fraction of sediments,the 3He/4He ratio of the nonmagnetic fractionhas also been used as an upper bound on3He/4HeTERR (Fourre 2004). Finally, it has beensuggested that step heating of samples may beable to separate terrigenous and extraterrestrial3He, based upon the observation in early studiesthat 4He is predominantly released at low tem-peratures (*400 �C), while 3He is mostlyreleased at[600 �C (Hiyagon et al. 1994; Farley2000). In this approach, He released below agiven temperature (e.g., 500 �C) is taken to beterrigenous, while the remainder of He is takento be extraterrestrial (Farley 2000); however,recent work employing additional heating stepsbetween 300 and 500 �C has found evidence forextraterrestrial He loss at temperatures of\500 �C (see Sect. 3.2) (Mukhopadhyay andFarley 2006). These recent results suggest thatthe step heating approach may underestimate3HeET concentrations as 15–30 % of 3HeET maybe released at temperatures \500 �C.

For studies in which the choice of 3He/4HeTERR

is critical but 3He/4HeTERR is not known, both lowerbound estimates (3He/4HeTERR = 2 9 10-8) andupper bound estimates using the approaches listedabove should be presented. Such an approachwould make it clear to the reader whether theassumptions with regards to the 3He/4HeTERR affectthe overall conclusions of the work.

3.2 Carrier Phase of 3HeET

in Terrestrial Deposits

3HeET in the geological record is retained for atleast 480 Ma (Patterson et al. 1998). However,the identity of the phase(s) responsible for long-term 3He retention remains unclear, which pre-sents a challenge in understanding how changingredox conditions or sedimentary diagenesis


affect the retention of 3He. Based on magneticseparations and chemical dissolution experi-ments performed on Quaternary sediments,magnetite and a second non-magnetic phase,probably a silicate, have been suggested as car-riers of 3HeET (Fukumoto et al. 1986; Amari andOzima 1988; Matsuda et al. 1990). The sug-gestion of magnetite as one of the carriers is,however, problematic. Magnetite in IDPs is notprimary but formed during atmospheric entryheating through oxidation of Fe–Ni sulfides,olivine, pyroxene, and poorly ordered silicates(Fraundorf et al. 1982; Brownlee 1985; Bradleyet al. 1988). Because magnetite formation duringentry heating will involve breaking chemicalbonds and diffusion of oxygen, pervasive loss of3He from the material undergoing the chemicaltransformation might be expected. 3He retentionin silicates is also problematic as the dominantsilicate phases in IDPs (olivines and pyroxenes)would be susceptible to diagenetic alteration onthe seafloor, while the layer lattice silicateswould have low retentivity for 3He. Finally,sequential chemical leaching on recent sedi-ments suggests that refractory phases such asdiamond, graphite, SiC, and Al2O3 do notaccount for more than 10 % of the 3HeET

(Fukumoto et al. 1986).More recently, Mukhopadhyay and Farley

(2006) carried out chemical leaching experimentsof the magnetic and non-magnetic fraction ofgeologically old sediments (up to 90 Ma). Theseexperiments indicate that similar amounts of 3Heare lost from the magnetic and non-magneticfractions and rule out organic matter and refrac-tory phases such as diamond, graphite, SiC, andAl2O3 as the carriers responsible for long-termretention of 3HeET. In addition, based on IRMacquisition, Mukhopadhyay and Farley (2006)showed that the magnetic moment of the mag-netic and non-magnetic fraction is similar. Theresult suggests that the magnetite separationtechnique they and all previous workers usedresults in approximately half of the magnetite stillresiding in the non-magnetic fraction. Thechemical leaching and the magnetic properties ofthe magnetic and non-magnetic fraction of thesediments combined suggest a single carrier that

might be Fe–Ni metal, Fe–Ni sulfides, or possiblymagnetite but more likely a phase that is associ-ated with magnetite. In IDPs collected from thestratosphere olivine and pyroxene grains are fre-quently rimmed by magnetite a few to a few tensof nm thick that forms during atmospheric entryheating (Bradley et al. 1988). Because magnetiteis stable on the ocean floor for tens of millions ofyears, the magnetite rims may armor the olivines,pyroxenes or poorly ordered silicates againstchemical alteration and may also explain theassociation of the 3He carrier(s) with magnetite.

The presence of a single carrier phase is alsostrongly supported by step heating experiments(Fig. 3) on the magnetic and non-magneticfraction of the sediments that demonstrate thatthe 3He release patterns in the two sedimentfractions are identical (Mukhopadhyay andFarley 2006). The step heating experimentsindicate two release peaks, one at low tempera-ture (350–400 �C) and one at higher temperature(600–750 �C). Previous work (Amari and Ozima1985, 1988; Hiyagon 1994) had not noticed thelow temperature peak as the step heating exper-iments started at temperatures in excess of500 �C. While Farley (2000) had observed a lowtemperature release peak from step heatingexperiments in sediments from Site 607B, the3He/4He ratio for the low temperature releasepeak was 0.1 RA and hence, the release wasassociated with crustal He. Additionally, the newstep heating experiments (Mukhopadhyay andFarley 2006) indicate a higher retentivity for 3Heover geologic time. For example, extrapolationdiffusivities obtained from high-temperature stepheating experiments (e.g., Amari and Ozima1985) to seafloor indicates that greater than 99 %of the extraterrestrial 3He is expected to be lost in50 Ma, which is at odds with the pelagic clay 3Herecord from the Central Pacific GPC3 core(Farley 1995). The new step heating experimentsindicate that about 20 % of the 3He will be lostthrough diffusion at seafloor temperatures after50 Ma, while sedimentary rocks exposed on theEarth’s surface for the same amount of timewould lose up to 60 % (Mukhopadhyay andFarley 2006). Additionally, if temperaturesexceed 70 �C during sediment diagenesis


extensive 3He loss is expected to occur ([90 %)after only a few hundred ka. Thus, care must betaken to compare the extraterrestrial 3He recordfrom different sites and tectonic environments.

3.3 Atmospheric Entry Heatingand Grain Size Distributionof 3HeET-Bearing IDPsin Terrestrial Deposits

Atmospheric entry heating modifies the extra-terrestrial noble gas content of incoming IDPs.Heating during entry causes thermal decompo-sition of phyllosilicates within IDPs as well asdiffusive loss and bubble rupture, all of whichcontribute to He losses (Stuart et al. 1999).Maximum entry temperatures are proportional tomass and entry velocity; as a result, larger IDPsand IDPs derived from comets (which tend tohave higher geocentric velocities than asteroid-derived IDPs) are more likely to be degassedbefore reaching Earth’s surface (Flynn 1989;Love and Brownlee 1991). Hence, 3He in sedi-ments will not reflect the relative abundance ofcometary versus asteroid IDPs that enter theEarth’s atmosphere but will rather be biasedtowards the accretion of asteroidal IDPs.

Farley et al. (1997) quantitatively modeled thegrain size distribution of IDPs capable of retaining

3HeET after atmospheric entry. Based upon theassumption that IDPs have implanted 3HeET todepths of few hundred nanometers—i.e., 3He issurface area-correlated rather than volume-corre-lated—and that 3HeET is lost in IDPs heated tomore than*600 �C, Farley et al. (1997) predictedthat 3HeET in terrestrial sediments should primar-ily ([70 %) be contained within IDPs between 3and 35 lm in diameter. If 3HeET is insteadassumed to be volume-correlated, a much broadergrain size distribution results, with [70 % of3HeET contained with grains ranging from *5 to150 lm (Farley et al. 1997). Overall, Farley et al.(1997) find that as a result of atmospheric entryheating, 3HeET-bearing IDPs represent only*0.5 % of the total IDP mass flux to Earth of40 ± 20 9 106 g/a (Love and Brownlee 1993)and *4 % of the total IDP surface area flux.

Since the entry-heating model predicts the sizedistribution of 3He-bearing particles in sediment(particles not heated to[600 �C), for a given IDPflux and sediment accumulation rate, one can cal-culate the minimum volume of sediment requiredto statistically sample the He-bearing IDPs so asnot to underestimate the 3He flux. Additionally,predictions can be made of the reproducibility of3He measurements in sediment aliquots of differentsizes (i.e., different area-time products) depend-ing upon whether 3He is surface area-correlated

Temperature (oC)

200 400 600 800 1000 1200 1400

Fra

ctio

n E

xtra

terr

estr

ial 3

He

0.00

0.04

0.08

0.12

0.16

0.20Bulk SedimentMagnetic FractionNon-magnetic Fraction

Fig. 3 Extraterrestrial 3He release patterns for bulk,magnetic and non-magnetic fractions of sediments fromstep heating experiments (Adapted from Mukhopadhyayand Farley 2006). Bulk sediments are from LL44-GPC3and DSDP Site 596B, while the magnetic and non-magnetic fractions are from LL44-GPC3 sediments.

Since multiple experiments for bulk, magnetic and non-magnetic fractions were carried out by Mukhopadhyayand Farley (2006), only the average release pattern forthe three sediment types has been shown. Note the verystrong similarity in the release patterns for all threesediment types


or volume-correlated (Farley et al. 1997).The reproducibility of replicate samples matchespredictions from model results if 3HeET is a sur-face-area correlated component rather than a vol-ume-correlated component (Farley et al. 1997;Patterson and Farley 1998; Mukhopadhyay et al.2001a). This suggests that 3HeET is primarilycontained in a large number of fine grains ratherthan a small number of large grains. Studies ofgrain size fractions of deep-sea sediments and icecore particulates also support a correlation of3HeET content with IDP surface area, finding*60–90 % of the total 3HeET within size fractions\35 lm (Fig. 4) (Mukhopadhyay and Farley2006; Brook et al. 2009; McGee et al. 2010).

Though all three studies find that 3HeET isprimarily contained in grains\35 lm, each pro-vides a slightly different estimate of the grain sizedistribution of 3HeET in terrestrial deposits. Datafrom a sample of Holocene Antarctic ice indicatea sharp peak in 3HeET-bearing grains between5 and 10 lm (Brook et al. 2009); analyses of sixsamples of Late Quaternary North Atlantic driftsediments indicate a broader peak between 0 and20 lm (McGee et al. 2010); and data from asample of 33 Ma North Pacific red clay suggest abroader distribution, with roughly equal 3HeET

inventories in the 0–13 and 13–37 lm fractionsand only slightly lower 3HeET inventories in the37–53 lm and[53 lm fractions (Mukhopadhy-ay and Farley 2006). The differences in thesestudies may have to do with differences in thetime-area product of the samples used (sampleswith higher time-area products, such as red clays,are more likely to sample rare large IDPs) or withthe different methods used for grain size separa-tion. Brook et al. (2009) passed ice melt throughfilters to separate grain size fractions, whileMcGee et al. (2010) used settling after adding achemical dispersant to reduce flocculation of finegrains, and Mukhopadhyay and Farley (2006)used settling without dispersant addition.Settling, and particularly settling without dis-persants, is unlikely to quantitatively remove finegrains from coarser size fractions, potentiallyleading to an overestimation of 3HeET inventoriesin coarser fractions.

Some large (50–400 lm) IDPs from Antarc-tic ice appear to have retained 3HeET of bothsolar and spallogenic origin (Fig. 1) (Stuart et al.1999), but the grain size and reproducibilitymeasurements cited above suggest that theserare large He-retentive particles do not contrib-ute substantially to the total 3HeET flux. Finally,

0 10 20 30 40 50 60 70 80 90 100Size (µm)

0

10

20

30

40

50

60

70

80

Fra

ctio

n o

f 3H

e ET (

%)

Antarctic ice

0

1

2

3

4

5

6

7

8

10 c

m2/y

r)

North Atlantic

North Pacific

Model

Fig. 4 Grain size distribution of 3HeET in terrestrialdeposits and a model of surface area delivery of He-retentive IDPs. Data (solid lines) reflects the percent ofthe total 3HeET in a given grain size fraction. Data fromHolocene Antarctic ice (Brook et al. 2009) and 33 MaNorth Pacific sediments (Mukhopadhyay and Farley

2006) represent one sample each, while data from theNorth Atlantic represent the average of six samples fromthe last glacial period and Holocene (McGee et al. 2010).Model results (dashed line) reflect the total IDP surfacearea delivered by different particle sizes heated to lessthan 650 �C during atmospheric entry (Farley et al. 1997)


we note that Lal and Jull (2005) proposed thatinstead of 3He in IDPs, spallogenic He withinfragments released by meteorites during atmo-spheric entry is a dominant source of 3HeET insediments. The hypothesis of Lal and Jull (2005)makes two predictions: (1) approximately 50 %of the 3He is in sediments coarser than 50 lmand (2) high 3He/4He ratios in sediments shouldbe associated with spallogenic Ne. As notedabove, the grain size distribution data andreproducibility of 3HeET measurements do notsupport 50 % of 3HeET being in grain sizeslarger than 50 lm. Further, high 3He/4He ratiosof 2–3 9 10-4 in sediments have been found tobe associated with solar wind Ne and not spall-ogenic Ne (Fukumoto et al. 1986; Matsuda et al.1990). Hence, data do not support the hypothesisthat fragmentation of meteorites in the atmo-sphere is the dominant contributor to 3He; theyare instead best explained by 3HeET in marinesediments and terrestrial ice being a surface-areacorrelated component in IDPs.

4 Extraterrestrial Hein the Geologic Record

4.1 Extraterrestrial He as a Tracerof Past Variations in IDP Flux

As a tracer of the IDP flux, 3HeET offers a viewinto past accretion rates of extraterrestrial matterthat is quite different from that provided by irid-ium and other PGEs, which trace the total extra-terrestrial mass flux. As demonstrated below, largeimpacts that leave PGE anomalies may or may notbe accompanied by elevated IDP fluxes (Farleyet al. 1998; Mukhopadhyay et al. 2001a, b), andelevated IDP fluxes are not always accompaniedby large impacts (Farley et al. 2006).

3HeET fluxes fHeETð Þ are calculated by multi-plying the measured 3HeET concentration by thesedimentary mass accumulation rate (MAR):

fHeET ¼ 3HeET

� ��MAR

� �=R ð2Þ

where [3HeET] is the 3HeET concentration in thesediment (see Eq. 1), MAR is the sedimentary

mass accumulation rate and R is the fractionalretentivity of 3He (Farley 1995). Though assump-tions of constant inputs of hydrogenous cobalt haveoccasionally been used for MAR calculation(Farley 1995), MARs are usually derived from agemodels:

MAR ¼ q � Dz

Dtð3Þ

where q is the dry bulk density, Dz is a depthinterval, and Dt is the time associated with thatdepth interval. Age models are typically deter-mined from geologic epochs, magnetic chrons orastronomical tuning (e.g., Farley 1995; Farleyet al. 1998, 2006; Mukhopadhyay et al. 2001a)and are thus subject to errors in the ages of epochor chron boundaries or in the identification ofastronomical cycles. Age model-based MARsalso do not account for sedimentary inputs bylateral advection or slumping. As a result ofpotential age model errors and spurious 3HeET

flux changes caused by changes in lateraladvection of sediments, some studies havesought to replicate 3HeET flux excursions inmultiple cores or sections (e.g., Farley et al.1998, 2006). Finally, 3HeET retentivity in thesedimentary record over geological time is notwell quantified, and thus the value of R is notknown. As a result, the absolute 3HeET fluxcannot be determined. Rather, one alwayscalculates the product fHeET � R and the product istermed the implied 3HeET flux (e.g., Farley et al.1998; Mukhopadhyay et al. 2001a). We note that3HeET loss by diffusion is expected to increasewith age; i.e., R should decrease monotonicallywith age. However, because 3HeET is retained inthe geological record for at least 480 Ma(Patterson et al. 1998), assuming an invariantR in a given sedimentary setting is probably validover the geologically short (*a few to a few tensof Ma) timescales over which IDP flux variationswould be expected to occur (Farley et al. 1998,2006). Thus, relative variations in 3HeET fluxesin the sedimentary record over million-yeardurations are robust even though the absolutevalues of the fluxes may not be well defined.

The discovery of 3HeET in 480 Ma Ordovicianlimestones (Patterson et al. 1998) suggests that


IDP accretion rates could be reconstructed overmost of the Phanerozoic. The implied accretionrate of extraterrestrial 3He in the Late Ordovicianis*0.5 ±0.2 pcc STP/cm2/ka, which is similar tothe average flux over the Cenozoic. The Ordovi-cian sediments further demonstrate that 3HeET insediments is largely carried by IDPs, as co-exist-ing meteorites in the sedimentary section have Heconcentrations that are similar to or only slightlyhigher than the 3He concentration of the hostlimestones.

At the Permo-Triassic boundary (P/Tr) sec-tions at Meishan, China and Sasayama, Japan,3HeET has been reported, although not in IDPs butrather in fullerenes delivered through a bolideimpact (Becker et al. 2001). However, Farley andMukhopadhyay’s (2001) measurements of 3Hefrom the Meishan section did not detect 3HeET ator near the vicinity of the P/Tr boundary and thus,they found no evidence for fullerene-hosted

3HeET. Additional work by Farley et al. (2005)from the Opal Creek P/Tr section in Canada alsofound no evidence of extraterrestrial 3He, andhence, fullerene-hosted 3HeET. As a result, whe-ther or not fullerene-hosted 3HeET is present at theP/Tr boundary remains an open question.

In spite of 3HeET being retained for the past480 Ma, 3He fluxes are relatively well charac-terized only for the Cenozoic. The Cenozoichistory of 3HeET fluxes was first investigated byFarley (1995) in core LL44-GPC3 from thecentral North Pacific. The study found roughlyconstant 3HeET fluxes averaged over epochs fromthe Late Cretaceous to the Pliocene (*0.5±0.2 pcc STP/cm2/ka), with highest fluxes in theOligocene and lowest fluxes in the Miocene(Fig. 5). 3HeET fluxes were also calculated bynormalizing to Co concentrations in the sediment,based on the assumption that hydrogenous Coaccumulates at a constant rate (Kyte et al. 1993).

0 10 20 30 40 50 60 70Age (Ma)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

3H

e ET

2/k

a)

ODP 690 (Southern Ocean)

ODP 1266 (S Atlantic)

ODP 1209 (N Pacific)

LL44-GPC3 (N Pacific) Italian Apennines

ODP 757 (Trop Indian)

ODP 926 (Eq Atlantic)

3.8

Fig. 5 Records of 3HeET flux from the late Cretaceous tothe Pleistocene. Records from LL44-GPC3, ODP 690, ODP1209 and ODP 1266 represent the average 3HeET fluxesacross dated intervals. Records from ODP 757 and ODP926 reflect the 3-point moving average of ‘‘instantaneous’’3HeET fluxes (i.e., the product of a sample’s 3HeET

concentration and MAR derived from the age model). Datafrom the Italian Apennines reflect the authors’ best estimatebased on chron-averaged 3HeET fluxes, 3HeET

concentrations normalized to the non-carbonate fraction,and 3He/4He ratios. The short-lived flux increases at 35 and8 Ma are shown in greater detail in Fig. 6. Differences inabsolute fluxes between records are likely to reflectdifferences in 3HeET preservation or sediment focusing.LL44-GPC3: Farley (1995). ODP 690: Farley and Eltgroth(2003). ODP 1209: Marcantonio et al. (2009). ODP 1266:Murphy et al. (2010). Italian Apennines: Mukhopadhyayet al. (2001a). ODP 757 and ODP 926: Farley et al. (2006)


Co-based fluxes of 3HeET can be calculated atmuch higher resolution than epoch-averagedfluxes and show high short-term variability,including peaks just before the K/Pg boundaryand during the early Eocene and latest Eocene/early Oligocene. Of these, the first is related toCo-based accumulation rates and is not reflectedin 3HeET concentrations, while the latter two aremarked by increased 3HeET concentrations in thesediments. One of the most dramatic features ofthe GPC3 record is a factor of 2 increase in the3HeET flux from the Pliocene to the Quaternary.This change could reflect (1) a change in IDP flux,(2) diffusional loss of 3HeET, (3) an age modelerror that places the Quaternary/Plioceneboundary too high in the core, or (4) increasedlateral advection of sediments to the site duringthe Quaternary. The Quaternary/Pliocene changein 3HeET flux has not been studied at other sitesand offers an important avenue for future work.

Subsequent work investigated the Creta-ceous-Eocene portion of the record in greaterdetail in pelagic limestones exposed in theUmbria-Marche basin of the Italian Apennines(Farley et al. 1998; Mukhopadhyay et al. 2001a).The mean 3HeET flux in the Apennine sections isa factor of 3–5 lower than the mean flux over thesame period in the North Pacific core studied byFarley (1995), suggesting either 3HeET lossduring the burial and uplift of this section(Mukhopadhyay and Farley 2006) or systemati-cally higher lateral advection of sediments at theNorth Pacific site. Mukhopadhyay et al. (2001a)found approximately constant 3HeET fluxes fromthe late Cretaceous through the early Eocene inpelagic limestones in the Italian Apennines.Possible departures from a constant flux occurnear the Paleocene/Eocene boundary, with a2–4-fold increase in 3HeET flux, and during theearly Eocene, when a gradual decrease in flux isindicated; however, there are concerns abouttectonic disturbances and slumping in thissection (Mukhopadhyay et al. 2001a). Signifi-cantly, there is no evidence for an increase in3HeET flux associated with the K/Pg boundary ineither the Apennines or an expanded K/Pgsection in Morocco. A single asteroid or cometimpact is not accompanied by increased

accretion rate of IDPs, while a shower of cometsgenerated by perturbation of the Oort cloudleads to an increased terrestrial IDP accretionrate associated with multiple impacts (Farleyet al. 1998). Hence, the K/Pg 3He results suggestthat the impactor was not part of a comet showerbut rather an asteroid or a lone comet(Mukhopadhyay et al. 2001a, b).

In the latest Eocene, 3HeET fluxes recon-structed from limestones in the Italian Apenninesand from an Indian Ocean sediment core docu-ment a factor of *5.5 increase in the IDPaccretion rate, with peaks at *36 and 35 Ma(Farley et al. 1998, 2006). The peaks areaccompanied by spikes in Ir concentration inthe Apennine section and roughly correspond tothe ages of the Chesapeake Bay and Popigaiimpact structures and tektite layers found insediments around the world (Fig. 6). The impliedincrease in IDP flux begins 0.7 Ma before the firstIr spike and gradually decays for almost 1 Maafter the second spike. Two potential mechanismscan account for the simultaneous increase in IDPaccretion rates and the delivery of large impac-tors: a comet shower associated with a perturba-tion of the Oort cloud or a large collision in theasteroid belt. Farley et al. (1998) preferredthe comet shower hypothesis because (1) theobserved variations in the dust flux matched Hutet al.’s (1987) predictions of dust enhancement inthe inner solar system associated with a cometshower generated by perturbation of the Oortcloud and (2) comet showers would necessarilylead to an increase in both dust and large imp-actors in the inner solar system. While largecollisions in the asteroid belt can enhance dustaccretion rates to the Earth, simultaneous deliv-ery of large impactors and dust is not predicted apriori, unless the collision occurs in the closevicinity of one of the several secular and mean-motion resonances in the asteroid belt from whichlarge objects can be ejected on Earth-crossingorbits on timescales of \1 Ma (e.g., Gladmanet al. 1997). Furthermore, it is not clear whetherthe enhancement in dust accretion rate fromasteroid belt collisions would match the observedpattern seen in the late Eocene (Farley et al.1998). Recent work, however, has suggested an


L-chondrite composition for the Popigai impactor(Tagle and Claeys 2004) suggesting that theincrease in IDP flux may have an asteroidalorigin.

3HeET flux again increased transiently in thelate Miocene (8.2 Ma) (Fig. 6). The 3HeET fluxpattern recorded in sediment cores from both theIndian and Atlantic oceans is broadly similar tothat of the late Eocene (Farley et al. 2006); indetail, however, the increase in 3HeET during theMiocene occurs more abruptly than in the

Eocene event, rising a factor of *4 in\100 ka,followed by a *1.5 Ma decay to pre-eventlevels. Unlike the Eocene event, there are noknown large impacts of this age. Farley et al.(2006) provided evidence that the event reflectsthe breakup of a parent asteroid with a diametergreater than 100 km to form the Veritas familyof asteroid fragments, an event that has beenindependently dated to 8.3 ± 0.5 Ma (Nesvornyet al. 2003). The Veritas family currently orbitsat a distance of 3.17 AU and continues to be a

Fig. 6 Insights into past solar system events fromvariations in the 3HeET flux. Top—Comparison of lateMiocene 3HeET fluxes at two sites with flux changespredicted from a model of IDP creation and transportafter the Veritas asteroid break-up event (Farley et al.2006). An independent estimate for the age of this eventis shown at the top of the figure. I/K denotes thetransition from kaolinite to illite as the dominant claymineral at Site 926. Bottom—A Late Eocene increase in

3HeET flux measured in samples from the Italian Apen-nines (Farley et al. 1998). Independent ages of increasesin Ir concentration in marine sediments (a marker ofextraterrestrial impacts) and of the Chesapeake Bay andPopagai impact structures are shown. The solid lineindicates the modeled increase in IDP flux associatedwith a comet shower initiated by a perturbation of theOort cloud; the dashed line is the same result shifted upto reflect pre- and post-event baseline IDP fluxes


major source of IDPs to the zodiacal cloud(Nesvorny et al. 2006). The breakup event islikely to have formed abundant IDPs, but it isunlikely to have sent any large fragments intoEarth-impacting orbits (Farley et al. 2006).Though the link between the Veritas breakupand the 3HeET flux increase is compelling,remaining questions include (1) why modelsindicate a more prolonged decay of IDP fluxfollowing the event than is observed and(2) whether a similar peak in 3HeET flux isassociated with the Karin asteroid breakup eventdated to *5.8 Ma (Nesvorny et al. 2006).

Several studies have investigated the 3He-based IDP accretion rate during the Quaternary,as cyclic variations in IDP accretion rate weresuggested as a driver of the 100 ka glacial cycle(Muller and Macdonald 1995). Modeling of theterrestrial accretion rate of asteroid dust predicts100 ka variations in IDP accretion rate of up to afactor of 2, associated with changes in Earth’sorbital inclination (Kortenkamp and Dermott1998a). 3HeET fluxes from the Atlantic andPacific oceans over the last 2 Ma based onMARs derived from benthic d18O data do sug-gest a 100 ka periodicity in 3HeET fluxes overthe past 700 ka (Farley and Patterson 1995;Patterson and Farley 1998). Peak fluxes occurduring interglacial periods with variations inamplitude ranging from a factor of *1.5 to*3.5 between cycles and between cores. Sur-prisingly, however, the peaks in 3He fluxes are*180� (50 ka) out of phase with the predictedaccretion rate of IDPs based on orbital variations(Kortenkamp and Dermott 1998a). Hence, eitherthe observed peaks in 3HeET fluxes are not aconsequence of varying IDP accretion rate fromspace, or the models that predict IDP accretionrates based on variations in Earth’s orbitalparameters (Kortenkamp and Dermott 1998a)may not be fully capturing all of the accretionprocesses. For example, Dermott et al. (2001)suggested that accretion of asteroidal dust fromthe resonant ring of dust around the Earth maybe a possible mechanism for inducing a 50 kalag in the IDP accretion rate. This hypothesis hasyet to be verified.

The apparent variations in 3HeET flux duringthe late Quaternary have also been called intoquestion based on observations that the ratio of3HeET to scavenged 230Th—a tracer of sedi-mentary flux largely independent of age modelerrors and lateral advection of sediments—remains constant within ±40 % (one standarddeviation of the mean) through glacial-intergla-cial cycles in equatorial Pacific sediments, sug-gesting relatively constant 3HeET flux(Marcantonio et al. 1995, 1996, 1999, 2001b;Higgins et al. 2002) (see Sect. 4.2 for additionaldiscussion). Further, Winckler et al. (2004)found that age model-based 3HeET fluxes varywith a 41 ka periodicity in the early Quaternary;this period matches that of contemporaneousglacial-interglacial variability but does notmatch that of changes in orbital inclination.Winckler and Fischer (2006) also found nochanges in 3HeET fluxes in Antarctic ice fromthe last glacial period to the Holocene. Together,these results suggest that the observed 100 kacycles in late Quaternary 3HeET accumulation inmarine sediments are a consequence rather thana cause of climate variability, perhaps related toglacial-interglacial changes in sediment focusingor systematic age model errors caused byglacial-interglacial changes in carbonate disso-lution (Marcantonio et al. 1996, 2001b; Higginset al. 2002; Winckler et al. 2004). Variations inextraterrestrial 3He flux of smaller magnitude(±40 %), however, cannot yet be ruled out.

The variations in the 3He-based IDP accretionhistory discussed above have provided importantobservational evidence for hypothesized solarsystem events, such as the possible cometshower in the Late Eocene (Farley et al. 1998),the collision disruption of an asteroid to createthe Veritas family 8.3 at Ma (Farley et al. 2006),and the nature of the impactor at the K/Pgboundary (single impactor vs. comet shower).Furthermore, the 3He-based accretion historyover the past 70 Ma strongly refutes the specu-lative hypothesis that mass extinctions in thegeological record are driven by quasi-periodiccomet showers (Hut et al. 1987). While a cometshower may have occurred in the Late Eocene,


not a single extinction event over the past 70 Maappears to be associated with comet showers,and one of the largest mass extinction events ofthe Phanerozoic—the K/Pg boundary event—isclearly not associated with a comet shower(Mukhopadhyay et al. 2001a, b).

4.2 Use of Extraterrestrial 3Heto Calculate SedimentaryAccumulation Rates

When the 3HeET concentration in a sedimentarysection varies, it implies either a variation in theflux from space or changing MAR. If the fluxfrom space is taken to be constant, then Eq. 2can be inverted to solve for the sediment MAR.A constant 3HeET flux from space can often beinferred when 3HeET concentrations co-varywith concentrations of a terrigenous sedimentarycomponent (e.g., terrestrial 4He, Fe, or the non-carbonate fraction) or with concentrations of230Th scavenged from the water column. 3HeET-based MARs differ in several important respectsfrom MARs derived from age models. First,3HeET-based MARs can be calculated at eachsample depth for which 3HeET measurements areavailable, while MARs based on age models arecalculated as average values between age modeltie points. Second, over the last 400 ka(when 3HeET fluxes have been determined by230Th-normalization, as described below),absolute 3HeET-based MARs are independent ofsedimentary age models. Finally, if 3HeET-bearing IDPs are transported with laterallyadvected sediments, sediment focusing or win-nowing will not substantially change the mea-sured 3HeET concentration at a site; 3HeET-basedMARs will then ‘‘see through’’ sediment focus-ing and provide estimates of the vertical rain rateof sediment at a site (e.g., Marcantonio et al.2001b; McGee et al. 2010). In periods prior to400 ka, when 3HeET fluxes must be calculatedfrom sedimentary age models, the 3HeET fluxestimates may be biased by systematic focusingor winnowing in the sediment, affecting theabsolute value of 3HeET-based MARs but not therelative changes in MARs.

A critical first step in constructing 3He-basedMARs is testing whether 3HeET fluxes are in factconstant over a given period. In late Quaternarymarine sediments, 3HeET fluxes have been cal-culated using 230Th-normalization (Marcantonioet al. 1995, 1996; Higgins et al. 2002). Briefly,230Th-normalization relies on the approximationthat 230Th produced in the water column from thedecay of dissolved 234U (230Thxs) is scavenged bysinking particles more quickly than it can be lat-erally mixed as a dissolved species. The flux of230Thxs to the seafloor is then taken to be equal tothe (known) production rate of 230Th in the watercolumn, and MARs can be calculated as the ratioof the 230Th production rate to the decay-cor-rected230Thxs concentration in the sediment (for areview of 230Th normalization, see Francois et al.2004). 230Th-based MARs have the same prop-erties as 3HeET-based MARs mentioned above:namely, they can be computed at high resolution;they are largely independent of age model errors;and they should be only minimally affected bylateral advection of sediments. 230Th-normaliza-tion can only be used in sediments from thelast *500 ka due to the radioactive decay of230Th (half-life 75.7 ka).

Marcantonio et al. (1995, 1996, 2001b) andHiggins et al. (2002) found 3HeET/230Thxs ratiosin sediments to be constant to within ±40 %throughout the equatorial Pacific Ocean over thelast 200 ka with no systematic glacial-intergla-cial variability, supporting a near-constant fluxof 3HeET during this time period. When 230Thxs

measurements are used to calculate MARs, theseresults indicate an average 3HeET accumulationrate of 0.8 ± 0.3 pcc STP/cm2/ka in the lateQuaternary (Fig. 7; all flux estimates are givenas mean ± one standard deviation of the mean).Marcantonio et al. (1999) determined a similar230Thxs-based 3HeET flux in an eastern equatorialIndian Ocean core for the past 200 ka(1.1 ± 0.4 pcc STP/cm2/ka). In a core from theArabian Sea, 230Thxs-based 3HeET fluxes are0.4 ± 0.3 pcc STP/cm2/ka over the past 23 ka,lower than observed at other sites, for reasonsthat are not clear (see discussion below)(Marcantonio et al. 2001a).


Independent corroboration of 3HeET flux esti-mates from marine sediments comes from mea-surements of 3HeET in ice cores, which find 3HeET

accumulation rates ranging from 0.62 ± 0.14 to1.25 ± 0.18 pcc STP/cm2/ka in four sets ofsamples of ice from Greenland and Antarcticaover the last 30 ka (Brook et al. 2000, 2009;Winckler and Fischer 2006). Similar fluxes havealso been found using accumulation rates inferredfrom an age model in Quaternary samples fromthe North Pacific core studied by Farley (1995)(*1.2 pcc STP/cm2/ka) and in equatorial Pacificsediments from the early Quaternary between1.36 and 1.6 Ma (0.73 ± 0.18 pcc STP/cm2/ka)(Winckler et al. 2004). Taken together, theseresults suggest approximately constant (±40 %)3HeET fluxes over the past 1.6 Ma and minimallatitudinal variations in 3HeET flux, providing abasis for using 3HeET for calculating MARs overthis time period. Importantly, these studiesestablish 3HeET as the only constant flux proxyavailable for paleoflux studies in sediments priorto 500 ka.

3HeET can also been used as a constant fluxproxy for MAR calculations in studies rangingback to at least the K/Pg boundary, if 3HeET

fluxes from space and the fraction of original3HeET lost to diffusion are roughly constant overthe timescale of interest. The first assumptiondoes not hold during the late Eocene and lateMiocene (see Sect. 4.1), and the second may notbe appropriate in transitions between oxic andanoxic sediments, but in much of the lateCretaceous and Cenozoic they appear reason-able. In the carbonate-rich sections that havebeen studied, 3HeET concentrations are relativelyconstant with respect to the non-carbonatefraction, a rough indicator of relative sedimen-tation rates, supporting an approximately con-stant 3HeET flux (e.g., Mukhopadhyay et al.2001a, b; Farley and Eltgroth 2003; Marcantonioet al. 2009).

3HeET fluxes for these earlier periods aretypically determined in portions of a given sed-imentary section in which the age model is wellconstrained (usually by orbital tuning or mag-netostratigraphy) and that either are adjacent toor span the period of interest. These 3HeET fluxesare then applied to the interval of interest, whichis often a time of substantial changes in sedi-mentation when orbital signals are in doubt.Absolute 3HeET fluxes for a given time periodvary from site to site due to differences in 3HeET

preservation or sediment focusing (Fig. 5); forexample, 3HeET fluxes for the late Eocene andearly Paleocene are a factor of 3 or more higherin sediment cores from the central and westernNorth Pacific, South Atlantic and SouthernOcean (Farley 1995; Farley and Eltgroth 2003;Marcantonio et al. 2009; Murphy et al. 2010)than in a sediment core from Blake Nose in theNorth Atlantic (Farley and Eltgroth 2003). To theextent that these differences reflect differences insediment focusing (which increases 3HeET fluxesduring a dated interval by laterally advectingIDPs to a core site), 3HeET-based MARs will besystematically biased low in sites with highfocusing but relative changes in accumulationrates will still be robust. As noted above, absolute3HeET-based MARs are not independent of the

1 2 3 4

Eq. Indian

(0-2

00 ka

)5

Arabian

Sea

(0-2

3 ka)6

Antarc

tic ic

e (Holo

cene)

7

Antarc

tic ic

e (Holo

cene)

8

Antarc

tic ic

e (0-

29 ka

)9

Green

land ic

e (Holo

cene)

7

0.0

0.5

1.0

1.53H

e ET F

lux

(pcc

/cm

2/k

a)230Th-basedAge model-based

Fig. 7 Estimates of the Quaternary 3HeET flux. Fluxesare estimated using both sedimentary and ice core agemodels (open circles) and using 230Th-normalization(closed circles). 1-sigma confidence intervals are shown.Most estimates are consistent with a flux of 0.8 ± 0.3 pccSTP 3HeET/cm2/ka (indicated by the line and shadedbox). The results do not suggest a latitudinal dependenceof 3HeET flux. Data sources: Marcantonio et al. (1995),Higgins et al. (2002), Winckler et al. (2004), 4Farley(1995), Marcantonio et al. (1999), Marcantonio et al.(2001a), Brook et al. (2000), Brook et al. (2009,Winckler and Fischer (2006)


chronology used to determine the mean 3HeET

flux, but relative MAR changes are independentof the chronology within a given core.

3HeET has been used as a constant flux proxyto estimate the duration of two prominent inter-vals of carbonate dissolution in the late Creta-ceous and early Cenozoic: the K/Pg boundaryclay and clays associated with the Paleocene-Eocene Thermal Maximum (PETM). Mukho-padhyay et al. (2001b) calculated the mean3HeET flux immediately prior to the K/Pgboundary from Gubbio in the Italian Apenninesand then used this flux combined with 3HeET

concentration data within the boundary clay todetermine sedimentation rates and the durationof the K/Pg boundary event (Fig. 8). This was theoriginal purpose of measuring Ir in the boundaryclay (Alvarez et al. 1980), but while the asteroidimpact created an Ir spike at the boundary, 3HeET

shows little change. This is to be expected as thelarge impactor should have been degassed andtherefore would not have left a 3He signature in

the sedimentary record. Dividing the density andthickness of the clay by the 3HeET-based MAR ofthe clay, Mukhopadhyay et al. (2001b) founddurations for the boundary event of only7.9 ± 1.0 ka and 10.9 ± 1.6 ka in two Apenninesections and 11.3 ± 2.3 ka in an expanded K/Pgsection in Tunisia.

Farley and Eltgroth (2003) and Murphy et al.(2010) used a similar approach to estimate theduration of the PETM carbonate dissolutionevent in sediment cores from the SouthernOcean (ODP Site 690), South Atlantic (ODPSite 1266) and North Atlantic (ODP Site 1051).All three cores had age models established byastronomical calibration (in which variations insediment composition are tuned to orbitalchanges) that had previously been used to esti-mate the durations of the onset, peak andrecovery phases of the carbon isotope excursionsand carbonate dissolution associated with theevent. Farley and Eltgroth (2003) determined amean 3HeET flux during two magnetic chronsspanning the PETM, while Murphy et al. (2010)determined the 3HeET flux over six eccentricitycycles preceding the event. These mean fluxeswere then combined with 3HeET concentrationdata from PETM sediments to estimate thedurations of each phase of the event. In eachcore, the 3HeET-based age model suggests thatthe peak duration of the carbon isotope excur-sion is longer, and the recovery period shorter,compared to results from cyclostratigraphy(Fig. 9) (Röhl et al. 2000, 2007; Farley and El-tgroth 2003; Murphy et al. 2010). If the 3HeET

age models are correct, the longer duration ofthe CIE suggests sustained release of light car-bon following the initial rapid burst of lightcarbon into the ocean–atmosphere system(Murphy et al. 2010). Determination of whetherthe 3HeET or cyclostratigraphic age-model iscorrect is also essential for evaluation ofhypothesized mechanisms for removing excesscarbon from the ocean–atmosphere systemduring and after the PETM. Additionally, the3HeET age-model from Site 690 (Farley andEltgroth 2003) suggests a faster pace of thePETM event compared to Site 1266 (Murphy

Fig. 8 3HeET-based sedimentation rates for the Creta-ceous-Paleogene boundary section at Gubbio, Italy(Mukhopadhyay et al. 2001b). Points indicate instanta-neous sedimentation rates, while the line is the three-point moving average. The diamond indicates thesedimentation rate in the K/Pg (K/T in the figure)boundary clay. Note that the sedimentation rate in theboundary clay is only a factor of *3 lower than insurrounding carbonate-rich layers. Based upon results atthis and two other sections, the authors determined aduration for the K/Pg boundary clay of only 8–11 ka. Bycombining sedimentation rate estimates with measure-ments of stratigraphic height, time relative to the K/Pgboundary can be estimated in the rest of the section


et al. 2010). The reason for this discrepancy isnot completely clear, but may be related to the3HeET flux calibration from Site 690.

3HeET-based MARs have also provided thebasis for a number of paleoflux studies. As3HeET-MARs can be calculated at much higherresolution than age model-based MARs, theyallow novel insights into variations in pastfluxes—for example, distinguishing whether anincrease in the terrigenous fraction of sedimentsis due to increased terrigenous flux or decreaseddilution by other sedimentary constituents.3HeET data from Farley and Eltgroth’s (2003)study have been used to determine accumulationrates of excess barium, a productivity proxy, inorder to demonstrate that marine productivity didnot play a major role in lowering atmosphericCO2 levels after the PETM (Torfstein et al.2010). Marcantonio et al. (2009) used 3HeET datato determine relative changes in bulk MARs andfluxes of dust and calcium carbonate during thelate Eocene prior to the PETM. In addition toidentifying orbitally-paced variations in

carbonate preservation, this study found thatorbital variations in aeolian dust deposition inthis greenhouse climate were similar in magni-tude to those observed in the icehouse climate ofthe late Pleistocene. Similarly, Winckler et al.(2005) used 3HeET-based MARs to determinefluxes of productivity-related trace elements(barium, aluminum, phosphorous) and dust in theequatorial Pacific during a 1 Ma period spanningthe mid-Pleistocene transition (MPT). Whileprevious studies normalized productivity proxiesto titanium and concluded that productivityincreased during the MPT, 3HeET-normalizedfluxes of productivity proxies indicate no changein productivity across the MPT and insteadindicate lower fluxes of titanium and 4He fromaeolian dust (Winckler et al. 2005).

Given the fact that sedimentary 3HeET appearsto be predominantly contained in parti-cles \20 lm in diameter (see Sect. 3.3), oneconcern in using 3HeET as a constant flux proxy isthat grain size fractionation during lateraladvection of sediments by ocean currents

Fig. 9 Age models for the Paleocene-Eocene ThermalMaximum (PETM) based on 3HeET (black) and cyclos-tratigraphy (red) (Murphy et al. 2010). The panels showthe d13C and calcium carbonate preservation changesassociated with the PETM at ODP Site 1266. Grey errorbars reflect the 2r uncertainty in the 3HeET-based agemodel based on the uncertainty of the 3HeET fluxcalibration for the interval. Note that in the 3HeET-based

age model, the duration of the carbon isotope excursion issignificantly longer than in the cyclostratigraphic agemodel, the recovery from the d13C excursion is more rapid,and the return to high carbonate preservation is slower.Arrows indicate the relative ages of the ends of two phasesof the PETM recovery estimated by the two methods, withthe 3HeET-based model indicating a slightly longer(*45 ka) total duration for the PETM event


(sediment focusing) will enrich focused sedi-ments in 3HeET-bearing IDPs. This fractionationwould increase 3HeET concentrations in sites ofsediment focusing while decreasing concentra-tions in winnowed sediments; 3HeET-basedMARs would then be biased low by sedimentfocusing and biased high by winnowing. Such aneffect was suggested by Marcantonio et al.(2001a), who observed 3HeET/230Thxs ratios in anIndian Ocean core a factor of 1.8 lower than atother sites. To test this suggestion, McGee et al.(2010) measured He and U-Th isotopes in sedi-ments from two cores on the Blake Ridge in thewestern North Atlantic. The cores are \10 kmapart and should thus receive similar verticalfluxes of sediment, but one core received muchgreater inputs of focused sediments over the past20 ka. Despite substantial differences in focus-ing, 3HeET-based MARs agree between the twosites and are largely consistent with 230Thxs-basedMARs. Though the uncertainties in 3HeET-basedMARs in this study are large due to uncertaintiesin the correction for terrigenous 3He, the resultssuggest that 3HeET-based MARs are not sub-stantially affected by lateral advection.

The work summarized above builds on theobservation that implied 3HeET fluxes at a givensite are largely constant over Ma timescales,allowing 3HeET to be used as a constant fluxproxy for determining sedimentary mass accu-mulation rates. In studies seeking to determinevariations in fluxes of sedimentary constituents,such as dust and paleoproductivity proxies, 3He-based MARs currently provide the only meansof obtaining data that are independent of agemodels and capable of resolving sub-orbital fluxvariations. (Many studies multiply point-by-point concentration data by longer-term averagefluxes determined from age models and give theappearance of sub-orbital resolution, but inreality these changes in concentration couldreflect either short-term changes in flux or short-term changes in dilution by other sedimentaryconstituents with no change in flux.) Applica-tions of 3He-normalization have provided novelinsights into the K/Pg and PETM events and into

changes in productivity and dust flux during thelate Eocene and the mid-Pleistocene transition.Even so, the use of 3HeET as a constant fluxproxy has been relatively limited compared to itspotential applications.

5 Summary and Future Work

Measurement of 3HeET in marine sediments hasprovided important insights into past changes inthe accretion rates of IDPs. Additionally, 3HeET

has shown promise as a constant flux proxycapable of quantifying sub-orbital variability inpast sedimentary fluxes and in constrainingsedimentary age models, particularly duringperiods of carbonate dissolution. In lookingahead to future work, several questions offerpromising avenues of research. These include:• Can we improve our ability to distinguish

3HeET from terrigenous 3He in detrital-rich,rapidly accumulating sediments such as con-tinental margin deposits or lake sediments?

• What phases are responsible for the long-termretention of 3HeET in marine sediments, and isthe stability of these phases affected bychanging redox conditions? Is 3HeET retainedin anoxic sediments, allowing 3HeET-basedstudies of ocean anoxic events?

• What is the relative importance of asteroidalvs. cometary sources of IDPs? Why do themeasured 3HeET fluxes not match the pre-dicted variability in IDP accretion rate overorbital timescales?

• What is the pace of environmental changeduring major climatic transitions? Severalmajor transitions—including those associatedwith the Eocene–Oligocene, Oligocene–Mio-cene, and Pliocene–Pleistocene boundaries—have not yet been studied at high resolution,and 3HeET is perhaps the best timekeeperavailable for such studies.

Acknowledgement The authors would like to thankKen Farley for reviewing this chapter.


References

Alvarez LW, Alvarez W, Asaro F, Michel HV (1980)Extraterrestrial cause for the cretaceous-tertiaryextinction: experimental results and theoretical inter-pretation. Science 208(4448):1095–1108

Amari S, Ozima M (1985) Search for the origin of exotichelium in deep-sea sediments. Nature 317(6037):520–522

Amari S, Ozima M (1988) Extraterrestrial noble gases indeep-sea sediments. Geochim Cosmochim Acta52(5):1087–1095

Andrews JN (1985) The isotopic composition of radio-genic helium and its use to study groundwatermovement in confined aquifers. Chem Geol49:339–351

Basu S, Stuart FM, Klemm V, Korschinek G, Knie K, HeinJR (2006) Helium isotopes in ferromanganese crustsfrom the central Pacific Ocean. Geochim CosmochimActa 70(15):3996–4006. doi:10.1016/j.gca.2006.05.015

Becker L, Poreda RJ, Hunt AG, Bunch TE, Rampino M(2001) Impact event at the permian-triassic boundary:Evidence from extraterrestrial noble gases in fuller-enes. Science 291:1530–1533

Benkert JP, Baur H, Signer P, Wieler R (1993) He, Ne,and Ar from the solar wind and solar energeticparticles in lunar ilmenites and pyroxenes. J GeophysRes 98(E7):13147–13162

Bradley JP, Sandford SA, Walker RM (1988) Interplan-etary dust particles. In: Kerridge J, Mathews MS (eds)Meteorites and the Solar System. University ofArizona Press, Tucson, pp 861–895

Brook EJ, Kurz MD, Curtice J (2009) Flux and sizefractionation of He-3 in interplanetary dust fromAntarctic ice core samples. Earth Planet Sci Lett286(3–4):565–569. doi:10.1016/J.Epsl.2009.07.024

Brook EJ, Kurz MD, Curtice J, Cowburn S (2000)Accretion of interplanetary dust in polar ice. GeophysRes Lett 27(19):3145–3148

Brownlee DE (1985) Cosmic dust: collection andresearch. Ann Rev Earth Planet Sci 13:147–173

Burns JA, Lamy PL, Soter S (1979) Radiation forces onsmall particles in the solar-system. Icarus 40(1):1–48

Dermott SF, Grogan K, Durda DD, Jayaraman S,Kehoe TJJ, Kortenkamp SJ, Wyatt MC (2001) Orbitalevolution of interplanetary dust. In: Grün E,Gustafson BÅS, Dermott SF, Fechtig H (eds) Inter-planetary dust. Springer, Berlin, pp 569–641

Du XQ, Wang YH, Ren JG, Ye XR, Lu HY (2007)Helium isotope investigation on magnetic reversalboundaries of loess-paleosol sequence at Luochuan,central Chinese Loess Plateau. Chin Sci Bull52(17):2407–2412

Farley KA (1995) Cenozoic variations in the flux ofinterplanetary dust recorded by He-3 in a deep-seasediment. Nature 376(6536):153–156

Farley KA (2000) Extraterrestrial helium in seafloorsediments: identification, characteristics, and accretionrate over geologic time. In: Peucker-Ehrenbrink B,

Schmitz B (eds) Accretion of extraterrestrial mat-ter throughout Earth’s history. Kluwer, New York,pp 179–204

Farley KA, Eltgroth SF (2003) An alternative age model forthe Paleocene-Eocene thermal maximum using extra-terrestrial He-3. Earth Planet Sci Lett 208(3–4):135–148. doi:10.1016/S0012-821x(03)00017-7

Farley KA, Love SG, Patterson DB (1997) Atmosphericentry heating and helium retentivity of interplanetarydust particles. Geochim Cosmochim Acta 61(11):2309–2316

Farley KA, Montanari A, Shoemaker EM, Shoemaker CS(1998) Geochemical evidence for a comet shower inthe late eocene. Science 280(5367):1250–1253

Farley KA, Mukhopadhyay S (2001) An extraterrestrialimpact at the permian-triassic boundary? Science293:2343

Farley KA, Patterson DB (1995) A 100-Kyr periodicityin the flux of extraterrestrial He-3 to the sea floor.Nature 378(6557):600–603

Farley KA, Vokrouhlicky D, Bottke WF, Nesvorny D(2006) A late miocene dust shower from the break-upof an asteroid in the main belt. Nature 439(7074):295–297. doi:10.1038/Nature04391

Farley KA, Ward P, Garrison G, Mukhopadhyay S(2005) Absence of extraterrestrial He-3 in permian-triassic age sedimentary rocks. Earth Planet Sci Lett240(2):265–275. doi:10.1016/J.Epsl.2005.09.054

Fireman EL, Kistner GA (1961) The nature of dust collectedat high altitudes. Geochim Cosmochim Acta 24:10–22

Flynn GJ (1989) Atmospheric entry heating: a criterion todistinguish between asteroidal and cometary sourcesof interplanetary dust. Icarus 77(2):287–310

Fourre E (2004) A 475 kyr record of extraterrestrial 3Heand 230Th in North Atlantic sediments: caveats toderive MAR from these tracers. Eos Trans AGU85(47):Fall Meet Suppl, Abstract PP33A–0910

Francois R, Frank M, van der Loeff MMR, Bacon MP(2004) Th-230 normalization: an essential tool forinterpreting sedimentary fluxes during the late quater-nary. Paleoceanography 19(1):PA1018. Doi: 10.1029/2003PA000994

Fraundorf P, Brownlee DE, Walker RM (1982) Laboratorystudies of interplanetary dust. In: Wilkening LL (ed)Comets. University of Arizona Press, Tucson, pp 383–409

Fredriksson K (1956) Cosmic Spherules in Deep-SeaSediments. Nature 177(4497):32–33

Fredriksson K, Gowdy R (1963) Meteoric debris from thesouthern California desert. Geochim CosmochimActa 27:241–243

Fredriksson K, Martin LR (1963) The origin of blackspherules found in Pacific islands, deep-sea sedi-ments, and Antarctic ice. Geochim Cosmochim Acta27:245–248

Fukumoto H, Nagao K, Matsuda J (1986) Noble gas studieson the host phase of high 3He/4He ratios in deep-seasediments. Geochim Cosmochim Acta 50:2245–2253

Futagami T, Ozima M, Nakamura Y (1990) Helium ionimplantation into minerals. Earth Planet Sci Lett101(1):63–67


http://dx.doi.org/10.1016/j.gca.2006.05.015

http://dx.doi.org/10.1016/J.Epsl.2009.07.024

http://dx.doi.org/10.1016/S0012-821x(03)00017-7

http://dx.doi.org/10.1038/Nature04391


Gladman BJ, Migliorini F, Morbidelli A, Zappala V,Michel P, Cellino A, Froeschle C, Levison HF,Bailey M, Duncan M (1997) Dynamical lifetimes ofobjects injected into asteroid belt resonances. Science277(5323):197–201

Grimberg A, Baur H, Bochsler P, Bühler F, Burnett DS,Hays CC, Heber VS, Jurewicz AJG, Wieler R (2006)Solar wind neon from Genesis: implications for thelunar noble gas record. Science 314:1133–1135. doi:10.1126/science.1133568

Higgins SM, Anderson RF, Marcantonio F, Schlosser P,Stute M (2002) Sediment focusing creates 100-kacycles in interplanetary dust accumulation on theOntong Java Plateau. Earth Planet Sci Lett203(1):383–397

Hiyagon H (1994) Retention of solar helium and neon inIDPs in deep-sea sediments. Science 263:1257–1259

Hut P, Alvarez W, Elder WP, Hansen T, Kauffman EG,Keller G, Shoemaker EM, Weissman PR (1987)Comet showers as a cause of mass extinctions. Nature329(6135):118–126

Kortenkamp SJ, Dermott SF (1998a) A 100,000-yearperiodicity in the accretion rate of interplanetary dust.Science 280(5365):874–876

Kortenkamp SJ, Dermott SF (1998b) Accretion ofinterplanetary dust particles by the Earth. Icarus135(2):469–495

Kurz MD, Kenna TC, Lassiter JC, Depaola DJ (1996) Heliumisotopic evolution of Mauna Kea: first results from the1 km drill core. J Geophys Res 101:11781–11791

Kyte FT, Leinen M, Heath GR, Zhou L (1993) Cenozoicsedimentation history of the central North Pacific:Inferences from the elemental geochemistry of coreLL44-GPC3. Geochim Cosmochim Acta 57(8):1719–1740

Laevastu T, Mellis O (1955) Extraterrestrial material in deep-sea deposits. Trans Am Geophys Union 36(3):385–389

Lal D, Jull AJT (2005) On the fluxes and fates of He-3accreted by the Earth with extraterrestrial particles.Earth Planet Sci Lett 235(1–2):375–390. doi:10.1016/J.Espl.2005.04.011

Love SG, Brownlee DE (1991) Heating and thermaltransformation of micrometeroids entering the Earth’satmosphere. Icarus 89(1):26–43

Love SG, Brownlee DE (1993) A direct measurement ofthe terrestrial mass accretion rate of cosmic dust.Science 262(5133):550–553

Love SG, Joswiak DJ, Brownlee DE (1994) Densities ofstratospheric micrometeorites. Icarus 111(1):227–236

Mamyrin BA, Tolstikhin IN (1984) Helium isotopes innature. Elsevier, Amsterdam

Marcantonio F, Anderson RF, Higgins S, Fleisher MQ,Stute M, Schlosser P (2001a) Abrupt intensification ofthe SW Indian Ocean monsoon during the lastdeglaciation: constraints from Th, Pa, and He iso-topes. Earth Planet Sci Lett 184(2):505–514

Marcantonio F, Anderson RF, Higgins S, Stute M,Schlosser P, Kubik P (2001b) Sediment focusing inthe central equatorial Pacific Ocean. Paleoceanogra-phy 16(3):260–267

Marcantonio F, Anderson RF, Stute M, Kumar N,Schlosser P, Mix A (1996) Extraterrestrial He-3 as atracer of marine sediment transport and accumulation.Nature 383(6602):705–707

Marcantonio F, Higgins S, Anderson RF, Stute M,Schlosser P, Rasbury ET (1998) Terrigenous heliumin deep-sea sediments. Geochim Cosmochim Acta62(9):1535–1543

Marcantonio F, Kumar N, Stute M, Andersen RF, SeidlMA, Schlosser P, Mix A (1995) Comparative study ofaccumulation rates derived by He and Th isotopeanalysis of marine sediments. Earth Planet Sci Lett133(3–4):549–555

Marcantonio F, Thomas DJ, Woodard S, McGee D,Winckler G (2009) Extraterrestrial He-3 in Paleocenesediments from Shatsky Rise: Constraints on sedi-mentation rate variability. Earth Planet Sci Lett287(1–2):24–30. doi:10.1016/J.Epsl.2009.07.029

Marcantonio F, Turekian KK, Higgins S, Anderson RF,Stute M, Schlosser P (1999) The accretion rate ofextraterrestrial He-3 based on oceanic Th-230 fluxand the relation to Os isotope variation over the past200,000 years in an Indian Ocean core. Earth PlanetSci Lett 170(3):157–168

Matsuda J, Murota M, Nagao K (1990) He and Ne isotopicstudies on the extraterrestrial material in deep-seasediments. J Geophys Res 95(B5):7111–7117

McGee D, Marcantonio F, McManus JF, Winckler G(2010) The response of excess Th-230 and extrater-restrial He-3 to sediment redistribution at the BlakeRidge, western North Atlantic. Earth Planet Sci Lett299(1–2):138–149. doi:10.1016/J.Epsl.2010.08.029

McGee D (2010) Reconstructing and interpreting the dustrecord and probing the plumbing of Mono Lake.Dissertation, Columbia University

Merrihue C (1964) Rare gas evidence for cosmic dust inmodern pacific red clay. Ann Ny Acad Sci 119(A1):351–367

Mukhopadhyay S, Farley KA (2006) New insights intothe carrier phase(s) of extraterrestrial 3He in geolog-ically old sediments. Geochim Cosmochim Acta70(19):5061–5073

Mukhopadhyay S, Farley KA, Montanari A (2001a) A 35Myr record of helium in pelagic limestones fromItaly: Implications for interplanetary dust accretionfrom the early Maastrichtian to the middle Eocene.Geochim Cosmochim Acta 65(4):653–669

Mukhopadhyay S, Farley KA, Montanari A (2001b) Ashort duration of the cretaceous-tertiary boundaryevent: evidence from extraterrestrial helium-3. Sci-ence 291(5510):1952–1955

Muller RA, Macdonald GJ (1995) Glacial cycles andorbital inclination. Nature 377(6545):107–108

Murphy BH, Farley KA, Zachos JC (2010) An extrater-restrial He-3-based timescale for the Paleocene-Eocene thermal maximum (PETM) from WalvisRidge, IODP Site 1266. Geochim Cosmochim Acta74(17):5098–5108. doi:10.1016/J.Gca.2010.03.039

Murray J (1876) On the distribution of volcanic debrisover the floor of the ocean—its character, source and


http://dx.doi.org/10.1126/science.1133568

http://dx.doi.org/10.1016/J.Espl.2005.04.011



http://dx.doi.org/10.1016/J.Gca.2010.03.039

some of the products of its disintegration anddecomposition. Proc R Soc Edinb 9:247–261

Nesvorny D, Bottke WF, Levison HF, Dones L (2003)Recent origin of the solar system dust bands.Astrophys J 591(1):486–497

Nesvorny D, Jenniskens P, Levison HF, Bottke WF,Vokrouhlicky D, Gounelle M (2010) Cometary originof the zodiacal cloud and carbonaceous micromete-orites. Implications for hot debris disks. Astrophys J713(2):816–836. doi:10.1088/0004-637x/713/2/816

Nesvorny D, Vokrouhlicky D, Bottke WF, Sykes M(2006) Physical properties of asteroid dust bands andtheir sources. Icarus 181(1):107–144. doi:10.1016/J.Icarus.2005.10.022

Nier AO, Schlutter DJ (1990) Helium and neon instratospheric particles. Meteoritics 25:263–267

Nier AO, Schlutter DJ (1992) Extraction of helium fromindividual interplanetary dust particles by step-heat-ing. Meteoritics 27(2):166–173

Nier AO, Schlutter DJ (1993) The thermal history ofinterplanetary dust particles collected in the Earth’sstratosphere. Meteoritics 28(5):675–681

Nier AO, Schlutter DJ, Brownlee DE (1990) Helium andneon isotopes in deep Pacific Ocean sediments.Geochim Cosmochim Acta 54(1):173–182

Patterson DB, Farley KA (1998) Extraterrestrial 3He inseafloor sediments: Evidence for correlated 100 kyrperiodicity in the accretion rate of interplanetary dust,orbital parameters, and Quaternary climate. GeochimCosmochim Acta 62(23/24):3669–3682

Patterson DB, Farley KA, Schmitz B (1998) Preservationof extraterrestrial He-3 in 480-Ma-old marine lime-stones. Earth Planet Sci Lett 163(1–4):315–325

Pepin RO, Palma RL, Schlutter DJ (2000) Noble gases ininterplanetary dust particles, I: the excess helium-3problem and estimates of the relative fluxes of solarwind and solar energetic particles in interplanetaryspace. Meteorit Planet Sci 35(3):495–504

Pepin RO, Palma RL, Schlutter DJ (2001) Noble gases ininterplanetary dust particles, II: excess helium-3 incluster particles and modeling constraints on inter-planetary dust particle exposures to cosmic-ray irra-diation. Meteorit Planet Sci 36(11):1515–1534

Röhl U, Bralower TJ, Norris RD, Wefer G (2000) Newchronology for the late paleocene thermal maximumand its environmental implications. Geology 28(10):927–930

Röhl U, Westerhold T, Bralower TJ, Zachos JC (2007)On the duration of the paleocene-eocene thermalmaximum (PETM). Geochem Geophy Geosy8:Q12002. doi:10.1029/2007GC001784

Stuart FM, Harrop PJ, Knott S, Turner G (1999) Laserextraction of helium isotopes from antarctic micro-meteorites: source of He and implications for the fluxof extraterrestrial He-3 to earth. Geochim CosmochimActa 63(17):2653–2665

Takanayagi M, Ozima M (1987) Temporal variation of3He/4He ratio recorded in deep-sea sediment cores.J Geophys Res 92(B12):12531–12538

Tagle R, Claeys P (2004) Comet or asteroid shower in thelate Eocene? Science 305(5683):492

Thiel E, Schmidt RA (1961) Spherules from the antarcticice cap. J Geophys Res 66(1):307–310

Tilles D (1962) Primordial gas in the Washington countymeteorite. J Geophys Res 67(4):1687–1689

Tolstikhin I, Lehmann BE, Loosli HH, Gautschi A (1996)Helium and argon isotopes in rocks, minerals, andrelated groundwaters: a case study in northern Swit-zerland. Geochim Cosmochim Acta 60(9):1497–1514

Tolstikhin IN, Drubetskoy ER (1975) The 3He/4He and(4He/40Ar)rad isotope ratios for earth’s crust. Geo-chem Int 12:133–145

Torfstein A, Winckler G, Tripati A (2010) Productivityfeedback did not terminate the paleocene-eocenethermal maximum (PETM). Clim Past 6(2):265–272

Wieler R, Grimberg A, Heber VS (2007) Consequences ofthe non-existence of the ‘‘SEP’’ component for noblegas geo- and cosmochemistry. Chem Geol 244:382–390

Winckler G, Anderson RF, Schlosser P (2005) EquatorialPacific productivity and dust flux during the mid-Pleistocene climate transition. Paleoceanography20(4): PA4025. doi:10.1029/2005pa001177

Winckler G, Anderson RF, Stute M, Schlosser P (2004)Does interplanetary dust control 100 kyr glacialcycles? Quatern Sci Rev 23(18–19):1873–1878. doi:10.1016/J.Quascirev.2004.05.007

Winckler G, Fischer H (2006) 30,000 years of cosmicdust in antarctic ice. Science 313(5786):491. doi:10.1126/Science.1127469

Zähringer J (1962) Ueber die Uredelgase in denAchondriten Kapoeta und Staroe Pesjanoe. Geochi-mica et Cosmochimica Acta 26(6):665-680. doi:10.1016/0016-7037(62)90045-5


http://dx.doi.org/10.1088/0004-637x/713/2/816

http://dx.doi.org/10.1016/J.Icarus.2005.10.022

http://dx.doi.org/10.1016/J.Icarus.2005.10.022

http://dx.doi.org/10.1029/2007GC001784

http://dx.doi.org/10.1029/2005pa001177

http://dx.doi.org/10.1016/J.Quascirev.2004.05.007

http://dx.doi.org/10.1126/Science.1127469

http://dx.doi.org/10.1016/0016-7037(62)90045-5

extraterrestrial he in sediments: from recorder of...

Documents