doi: 10.1038/ngeo2537 protracted development of ... · supplementary information for: protracted...

Tarhan et al. Supplementary Information of 67

Supplementary Information for: Protracted Development of Bioturbation through the Early Palaeozoic Era

Lidya G. Tarhan1,2*, Mary L. Droser2, Noah J. Planavsky1 and David T. Johnston3 1Department of Geology and Geophysics, Yale University, 210 Whitney Ave, New Haven, CT 06511; 2Department of Earth Sciences, University of California-Riverside, 900 University Ave, Riverside, CA 92521; 3Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St, Cambridge, MA 02138. *email: [email protected].

Palaeozoic Bioturbation and Infaunalisation

Previous work1–5 has documented that burrowing in the latest Ediacaran, at the Precambrian–

Cambrian transition and in the early Cambrian was shallow (≤ 2 cm depth). The exceptions, such

as Skolithos and Arenicolites, common in early Cambrian and younger nearshore, sandy, high-

energy environments (e.g., ref. 6) attained much greater depths. However, these structures, which

have been attributed to static filter-feeding rather than mobile deposit-feeding organisms2,7,

would have merely statically increased advection of bottom-waters into the sediment on a very

localized scale1,8, rather than mediating physical or chemical homogenization. Therefore, even

densely colonized ‘pipe rock’ does not represent well-mixed sediment.

Various workers1–2,4,9–11 have described earliest Cambrian advances in infaunalisation and

ichnogeneric diversity. However, systematic documentation of trends in sediment mixing—true

bioturbation by mobile deposit-feeding organisms, made from a jointly ichnological and

sedimentological perspective, as well as consideration of post-early Cambrian strata and on a

global scale, has hitherto been lacking. Recent work by Mangano and Buatois11, for instance,

although purporting to track early Cambrian mixed layer development, was derived largely by

culling the published literature for descriptions of lower Cambrian trace fossil assemblages and

assessing ‘mixing’ from examination of published photographs and collection-based individual

Protracted development of bioturbation through the early Palaeozoic Era

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NGEO2537

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specimens (only 20% of the units included in their study were examined in the field by the

authors, and these data are not presented in a stratigraphic context). Moreover, extent of

‘bioturbation’ was determined largely through ichnotaxonomic work and assignment of

ichnoethological (i.e. feeding or trophic strategy) categories to particular ichnogenera, rather than

sedimentological assessment of the extent to which sediment was mixed. Our study, in contrast,

attempts to track mixed layer development using a jointly sedimentological and paleontological

toolkit and a stratigraphically continuous, facies-controlled and global approach, spanning the

entirety of the early Palaeozoic (Cambrian–Silurian). The development of well-mixed sediments

has been invoked as a trigger for a wide range of geochemical, palaeobiological,

sedimentological and taphonomic phenomena, including changes in bioessential nutrient fluxes,

the cycling of redox-sensitive elements and seafloor oxygenation; declines in the diversity and

abundance of microbialites; the disappearance of the Ediacara Biota, Ediacara-style preservation

and matgrounds; the advent of the Cambrian Explosion; changes in lipid biomarker preservation;

changes in the stratigraphic character of event bedding and the decline of Burgess Shale-type

preservation12–22. Thus, firmer constraints upon the timing of the development of sediment

mixing are imperative.

Geologic Setting

The following units were included in this study (Supplementary Fig. 1): the lowermost Cambrian

Chapel Island Fm (Canada); lower Cambrian Uratanna Fm (Australia); lower Cambrian Wood

Canyon Fm (western USA); lower Cambrian Torreárboles Sandstone (Spain); lower Cambrian

Poleta and Harkless fms (western USA); lower to middle Cambrian Pioche Fm (and correlative



Bright Angel Shale) (western USA); lower to middle Cambrian Carrara Fm (western USA);

Supplementary Figure 1. Study localities. Areas of study from lower–middle Cambrian (red circles),

Cambro-Ordovician (yellow circles) and Ordovician–Silurian (blue circles) successions, including the

Great Basin, western USA (see inset map; from west to east: White-Inyo Mountains, CA [Harkless Fm];

Salt Spring Hills, CA [Wood Canyon Fm.]; Funeral Mountains, CA [Wood Canyon and Carrara fms];

Lida, NV [Poleta Fm]; Frenchman Mountain, NV [Pioche Fm.]; Pioche Mining District, NV [Pioche

Fm.]; House Range, UT [Pioche Fm.]); Newfoundland (Fortune Head [Chapel Island Fm.], Bell Island

[Beach, Powers Steps, Scotia and Grebes Nest Point fms]); southern Spain (Guadajira [Torreárboles

Sandstone]); South Australia [Uratanna Fm]; New South Wales [Bynguano Fm]; and the Appalachian

Basin of the eastern USA [Juniata, Tuscarora, Rose Hill, Clinch, Rockwood, Mifflintown, Red Mountain,

Herkimer and Bloomsburg fms].

Cambro-Ordovician Beach Fm (Canada); Cambro-Ordovician Bynguano Fm (Australia); Lower

to Middle Ordovician Wabana Group (Powers Steps, Scotia and Grebes Nest Point fms)

(Canada); Upper Ordovician Juniata Fm (eastern USA); Lower Silurian Tuscarora, Rose Hill,

Clinch and Rockwood fms (eastern USA); Lower to Upper Silurian Mifflintown and Red

Mountain fms (eastern USA); Middle Silurian Herkimer Fm (eastern USA) and Middle to Upper

Silurian Bloomsburg Fm (eastern USA). These units are characterised by fine-grained

heterolithic lithologies and are interpreted, on the basis of facies, fauna and palaeogeographic

reconstruction, to have been deposited under well-oxygenated normal marine conditions (pers.



observ.; ref. 23–36). The lithofacies and interpreted depositional environment of each of these

units is characterised in further detail below:

Chapel Island Formation—The lowermost Cambrian Chapel Island Formation (Fortune Head,

Newfoundland, Canada), which contains the GSSP for the Precambrian-Cambrian boundary,

consists of a well-exposed succession of thinly bedded heterolithic strata (Supplementary Fig. 6;

see end of Supplement). Stratigraphic successions surrounding the boundary stratotype in

Member 2 of the Chapel Island Formation are dominated by cm-thick packages of laminated

siltstone, separated by mm- to cm-scale sandstone beds. Bed junctions are well-defined and

typically planar. Evidence of bypass sedimentation, in the form of ‘floating’ sand-infilled

burrows and pot casts, is not uncommon. Trace fossils of the Treptichnus pedum and Rusophycus

avalonensis biozones are common. Both erosive sole structures, such as pot casts, and evidence

of soft sediment deformation are common, indicating rapid deposition in a rapidly subsiding

shallow shelfal environment subject to periodic high-energy, storm-mediated onshore to offshore

sediment transport5,23. Measured intervals of the Chapel Island Formation are characterised by

17% mm-scale, 61% mm- to cm-scale, 12% cm-scale and 10% cm- to dm-scale bedding.

Uratanna Formation—The lower Cambrian Uratanna Formation (Flinders Ranges, South

Australia, Australia), which records the regional Precambrian-Cambrian succession, consists of

mm- to cm-scale siltstone packages interbedded with mm- to cm-scale silty sandstone beds,

deposited as infill of megachannels cut into the underlying Rawnsley Quartzite. This thinly

bedded heterolithic succession coarsens and shallows upward into a sequence of thick (dm- to m-

scale) cross-bedded and ripple-topped sandstones and records a shelfal to shoreline sequence.



The Uratanna Formation, in addition to a rich assemblage of Cambrian trace fossils, also

contains Ediacara Biota fossils similar to Swarpuntia, as well as Kullingia scratch circles24.

Wood Canyon Formation—The lower Cambrian unnamed upper member of the Wood Canyon

Formation (Death Valley region, USA) is composed of interbedded siltstone and fine-

grained quartzitic sandstone. In the Death Valley region, stratigraphic exposures of the Wood

Canyon Formation are characterised by m-scale coarsening-upward successions, consisting of

mm-scale siltstone beds which grade upward into fine-grained, well-sorted quartz-arenite

quartzite. Quartzite beds are typically very fine- to fine-grained and range from mm-cm- to dm-

scale in thickness. Low-angle cross-laminae are common, bed junctions are commonly wavy and

upper bedding plane surfaces are characterised by symmetrical ripples. Olenellid trilobites and

trace fossils of the lower Cambrian Rusophycus avalonensis biozone are common. The upper

member of the Wood Canyon Formation encompasses a range of shallow nearshore and shelfal

passive margin settings25.

Torreárboles Sandstone—The lower Cambrian Torreárboles Sandstone (Guadajira,

Extremadura, Spain) consists of thinly (cm-scale) bedded quartzitic, very fine-grained sandstone

packages containing mm-scale siltstone interbeds (Supplementary Fig. 7; see end of

Supplement). Bed junctions are well defined and are typically planar or rippled, without

evidence for significant erosional exhumation. Symmetrical and interference ripples are

common, as are delicately preserved surficial erosional sedimentary structures (e.g., tool marks).

Trace fossils of the lower Cambrian Treptichnus pedum and Rusophycus avalonensis biozones

are common, particularly several ichnospecies of Rusophycus. Exposures of the Torreárboles



Sandstone at Guadajira record deposition in nearshore to shallow shelfal settings5,26. Measured

intervals of the Torreárboles Sandstone are characterised by 19% mm- to cm-scale and 81% cm-

scale bedding.

Poleta Formation—The lower Cambrian Poleta Formation (White-Inyo Mountains, western

USA) crops out in eastern California and western Nevada as part of the Neoproterozoic–lower

Palaeozoic White-Inyo succession. The lower member of the Poleta Formation contains thinly

bedded, siltstone- and sandstone-dominated packages interbedded with thinly bedded (cm- to

dm-scale) archaeocyathid-rich carbonates and capped by an archaeocyathid bioherm. For

purposes of this study, we focused upon the siliciclastic portions of the Poleta Formation, which

are characterised by interbedded mm-scale siltstones and mm- to cm-scale sandstones

(Supplementary Fig. 8; see end of Supplement). Heterolithic intervals of the Poleta Formation

contain common small-scale (mm- to cm-scale) trace fossils along bedding planes. Both the

Poleta and the overlying Harkless formations record deposition in the more distal (deeper-water)

shelfal region offshore of western Laurentia25. Measured intervals of the Poleta Formation are

characterised by 46% mm-scale, 35% mm- to cm-scale and 19% cm-scale bedding.

Harkless Formation—The lower Cambrian Harkless Formation (White-Inyo Mountains, western

USA) overlies the Poleta Formation as part of the Neoproterozoic–lower Palaeozoic succession

of the White-Inyo Mountains. Like the Poleta Formation, the Harkless Formation is characterised

by thinly bedded and thinly interbedded mm-scale siltstones and planar mm- to cm-scale

sandstones and burrowed bed junctions (Supplementary Fig. 9; see end of Supplement).

Carbonate interbeds are locally rare in the Harkless Formation, which records deposition in distal



settings of the ‘geosynclinal’ shelfal passive margin sequence that characterised the western

margin of Laurentia during the early Cambrian25. Measured intervals of the Harkless Formation

are characterised by 9% mm-scale, 42% mm- to cm-scale and 49% cm-scale bedding.

Pioche Formation—The lower–middle Cambrian Pioche Formation crops out throughout the

western USA and was examined in detail at Frenchman Mountain (southeastern Nevada), in the

House Range (western Utah) and in the Pioche Mining District (eastern Nevada). At all three

localities, the Pioche Formation is characterised by thinly bedded (mm- to cm-scale) heterolithic

successions and well-defined bed junctions. At Frenchman Mountain (Supplementary Fig. 10;

see end of Supplement), exposures of the Pioche Formation range from cm-scale packages of

siltstone containing mm- to cm-scale sandstone interbeds to mm- to cm-scale sandstone packages

characterised by silty bed junctions. In the House Range (Supplementary Fig. 11; see end of

Supplement), exposures of the Pioche Formation consist of mm- to cm-scale beds of very fine- to

fine-grained sandstone interbedded with mm-scale siltstone horizons. The upper member (also

known as the Tatow Member) of the Pioche Formation in the House Range contains carbonate-

rich sandstone and oncolitic sandy carbonate horizons. In the Pioche Mining District

(Supplementary Fig. 12; see end of Supplement), the Pioche Formation is characterised by

alternating packages of siltstone, commonly containing articulated trilobites, with sparse, mm-

scale interbeds of very fine-grained sandstone; and coarsening upward successions of very fine-

to fine-grained sandstone with silty interbeds, capped by cross-bedded very fine- to fine-grained

carbonate-rich sandstones and bioclastic carbonates. Bedding is coherent, with well-defined

junctions and evidence for significant erosional exhumation is uncommon. Delicately preserved,

mm-scale surficial sedimentary structures, such as tool marks, are common and frequently



abundant. Sclerites and articulated remnants of early and middle Cambrian trilobite (e.g.

Olenellus) and small shelly fossil horizons are common at both Frenchman Mountain and in the

Pioche Mining District, but rare in the House Range. Shallow-tier trace fossils are abundant and

commonly occur as dense assemblages along bedding planes at all examined localities where the

Pioche Formation is exposed. The Pioche Formation records deposition in shelfal (epeiric)

settings, ranging from cratonic or deltaic to deeper shelfal environments5,25. Measured intervals

of the Pioche Formation at Frenchman Mountain are characterised by 76% mm-scale, 2% mm-

to cm-scale and 22% cm-scale bedding; in the House Range by 7% mm-scale, 21% mm- to cm-

scale, 47% cm-scale, 13% cm- to dm-scale and 12% dm-scale bedding; and in the Pioche Mining

District by 23% mm-scale, 21% mm- to cm-scale, 34% cm-scale, 7% cm- to dm-scale and 16%

dm-scale bedding.

Carrara Formation—The lower to middle Cambrian Carrara Formation (Death Valley region,

western USA) crops out throughout the western USA, and is particularly prominent in the Death

Valley region of eastern California. The Carrara records a significant transition between the

predominantly terrigenous siliciclastic deposition recorded in Neoproterozoic and lower

Cambrian units of the Death Valley region and the carbonate platform facies recorded in middle–

upper Cambrian and Ordovician regional successions. The lower Cambrian Eagle Mountain

Member, which conformably overlies the Emigrant Pass Member of the Zabriskie Quartzite, is

the stratigraphically lowest member of the Carrara Formation and records the first of four to five

“grand cycles” of shallowing-upward successions in the Carrara Formation. The Eagle Mountain

Member consists of mm-scale beds of mudstone and siltstone, interbedded with mm- to cm-scale

sandstone beds (Supplementary Fig. 13; see end of Supplement). Sandstone beds are commonly



characterised by low-angle cross-lamination. Symmetrical ripples range from rare to common.

Tool-marked bed soles are also rare to common; where tool marks occur, they occur abundantly

and on a very fine scale (sub-mm- to mm-scale diameters; mm- to cm-scale lengths). The

thickness, grain size and frequency of sandstone beds increase from the base to the top of the

member. Similarly, the frequency of carbonate and carbonate-cemented sandstone beds notably

increases upsection. Carbonate-cemented sandstone beds are commonly characterised by

quartzitic, bioturbated junctions and carbonate-rich wackestone to packstone interiors. Olenellid

trilobite sclerites are commonly associated with both mudstone interbeds and carbonate-

cemented sandstone and carbonate interbeds; carbonate and carbonate-cemented packstones

contain sclerites and intraclasts of up to pebble size. This facies package suggests a subtidal,

shelfal marine setting subject to increasingly high-energy conditions, corresponding to a

shallowing environment and progradation of the carbonate platform25. Measured intervals of the

Carrara Formation are characterised by 56% mm-scale, 20% mm- to cm-scale, 13% cm-scale,

9% cm- to dm-scale and 1% dm-scale bedding.

Bell Island and Wabana groups—The Cambro-Ordovician Bell Island and Lower–Middle

Ordovician Wabana groups of Bell Island, Newfoundland, Canada consist of a thick (1000 m-

scale), well-exposed succession of siliciclastic, thin-bedded, heterolithic strata, interpreted to

have been deposited in a shallow marine to shelfal setting. In particular, the thinly interbedded

mudstones, siltstones and sandstones of the Beach Formation (Bell Island Group) and Powers

Steps, Scotia and Grebes Nest Point formations (Wabana Group), of probable Tremadocian-

Arenigian age (Ranger et al. 1984), contain prolific and exceptionally preserved trace fossil

assemblages. The Beach Formation (Supplementary Fig. 14–15; see end of Supplement) is



characterised by thinly bedded and sharply interbedded siltstone and sandstone horizons which

alternate between cm- to dm-scale sandstone-dominated packages, characterised by cross-

lamination and rippled tops and separated by silty interbeds; and cm-scale packages of mm-scale

siltstone beds containing mm- to cm-scale lenses, stringers or laminae of sandstone. The Powers

Steps Formation (Supplementary Fig. 16–17; see end of Supplement) is characterised by thin

packages of mm- to cm-scale very fine-grained sandstone interbedded with mm-scale siltstone

beds. Sandstone beds are commonly lenticular and characterised by low-angle cross-lamination.

Small-scale (mm- to cm-scale length, sub-mm to mm-scale width) tool marks, which are

common throughout the Bell Island and Wabana groups, are especially common along bedding

planes of the Powers Steps Formation. The Scotia Formation (Supplementary Fig. 17; see end of

Supplement) is characterised by thin (cm- to dm-scale) hematitic sandstone beds with silty

partings, alternating with oolitic ironstone beds. The Grebes Nest Point Formation

(Supplementary Fig. 18; see end of Supplement) is characterised by mm-scale mudstone and

siltstone horizons interbedded with cm-scale sandstones, which are commonly lenticular and

range from laminated and ripple-topped to well-churned and densely burrowed. Evidence for

strong or frequent erosion (rip-ups, scoured bed bases, truncation of burrows) is lacking and

evidence for even moderate-scale erosion is uncommon in the Bell Island and Wabana groups.

Dense, diverse and well-preserved trace fossil assemblages are common throughout the Bell

Island and Wabana groups. Soft sediment deformation is not uncommonly observed in sandy

intervals, suggesting, in conjunction with cross-laminated horizons and a general lack of trace

fossil compaction, that deposition of sand-rich intervals occurred fairly rapidly. The above

lithological and sedimentological data indicate a shallow marine origin, ranging from storm-

dominated nearshore or deltaic to shelfal settings27,28. Measured intervals of the Powers Steps



and Scotia Formations are characterised by 31% mm-scale, 5% mm- to cm-scale, 38% cm-scale,

11% cm- to dm-scale and 16% dm-scale bedding. Measured intervals of the Grebes Nest Point

Formation are characterised by 65% mm-scale, 23% cm-scale and 12% dm-scale bedding.

Measured intervals of the Beach Formation are characterised by 1% mm-scale, 4% mm- to cm-

scale, 46% cm-scale, 20% cm- to dm-scale, 21% dm-scale and 9% m-scale bedding.

Bynguano Formation—The Cambro-Ordovician (Tremadocian?) Bynguano Formation

(Mootwingee, New South Wales, Australia) of New South Wales, Australia, consists of thinly

bedded (cm- to dm-scale) cross-bedded to planar-laminated to ripple-bedded quartzitic

sandstones interbedded with mudstones and siltstones (Supplementary Fig. 19; see end of

Supplement). Symmetrical ripple-topped bedding planes are common. The Bynguano Formation

contains diverse, architecturally complex and well-preserved trace fossil assemblages, notably

the anomalous capture of both Rusophycus-dominated ‘pre-depositional’ and Skolithos-

dominated ‘post-depositional’ assemblages associated with individual bedding planes. Trilobites

occur in the lower portion of the section. Evidence for erosion locally ranges from rare to

common. The Bynguano Formation is interpreted to have been deposited in a shallow marine

shelf (above storm wavebase) subject to alternating low- and episodic high-energy conditions29.

Juniata Formation—The Upper Ordovician (Ashgillian) Juniata Formation (Appalachian Basin,

eastern USA) is characterised by mm- to dm-scale fine-grained sandstone beds interbedded with

mm-scale siltstone beds (Supplementary Fig. 20–21; see end of Supplement). These heterolithic

sequences are packaged either as cm- to dm-scale very fine- to fine-grained sandstone beds

containing siltstone interbeds or silty partings; or as cm-scale siltstone packages containing mm-



scale sandstone lenses or thin interbeds. Sandstones range from planar- to cross-laminated and

ripple-topped. Bed bases range from planar to wavy to scoured. Mudstone and siltstone

intraclasts occur rarely to commonly along the bases of thicker sandstone beds. Siltstones are

burrowed; thinner (mm- to low cm-scale) sandstones are characterised by burrowed bed tops and

bases and muddier (‘scrambled’ or mixed) lithologies. Thicker sandstones (cm- to dm-scale),

however, are commonly laminated. Sandstone bed bases are characterised by dense trace fossil

assemblages, preserved via infill and casting of the underlying siltstone, and typically dominated

by Rusophycus. Pot casts are not uncommon. The Juniata Formation is, in the examined sections,

interpreted to record deposition in a shallow marine, passive margin deltaic environment30.

Measured intervals of the Juniata Formation are characterised by 29% mm-scale, 7% mm- to cm-

scale, 23% cm-scale, 33% cm- to dm-scale and 8% dm-scale bedding.

Tuscarora Formation—The Lower Silurian (Llandoverian) Tuscarora Formation (Appalachian

Basin, eastern USA) is characterised by mm- to dm-scale fine-grained sandstone beds

interbedded with mm-scale mudstone and siltstone beds (Supplementary Fig. 22; see end of

Supplement). These heterolithic sequences are packaged either as cm- to dm-scale very fine- to

fine-grained sandstone beds containing mudstone or siltstone interbeds, silty partings or mud-

draped cross-laminae; or as cm-scale siltstone packages containing mm-scale sandstone lenses or

stringers. Sandstones range from planar- to cross-laminated and ripple-topped. Siltstones are

burrowed; thinner sandstones are characterised by burrowed bed tops and bases and muddier

(‘scrambled’ or mixed) lithologies. Bed tops and the upper portion of sandstone beds are not

uncommonly well burrowed. Thicker sandstones, however, are commonly laminated. Sandstone

bed bases are characterised by dense assemblages of trace fossil assemblages, preserved via



casting of the upper surface of the underlying siltstone, and are typically dominated by

Arthrophycus. The Tuscarora Formation is regionally interpreted to record both pre-

transgressional deposition in shallow, shelfal, wave-dominated settings and transgressional

deposition under conditions of glacioeustatic sea level rise and/or thrust loading-mediated active

subsidence in a foreland basin setting31,32. Measured intervals of the Tuscarora Formation are

characterised by 31% mm-scale, 9% cm-scale, 14% cm- to dm-scale, 27% dm-scale, 12% dm- to

m-scale and 7% m-scale bedding.

Clinch Formation—The Lower Silurian (Llandoverian) Clinch Formation (Appalachian Basin,

eastern USA) is characterised by mm- to cm-scale fine-grained sandstone beds interbedded with

mm-scale mudstone and siltstone beds and occasional dm-scale fine-grained sandstone beds

(Supplementary Fig. 23; see end of Supplement). Sandstone bedforms are commonly topped by

symmetrical or interference ripples and range from continuous to lenticular to stringers.

Channelized sandstone bases are not uncommon. Rare low-angle cross-laminae are also observed

in sandstone beds. Pot casts and brachiopod and pebble lags occur rarely along sandstone bed

bases. The Clinch Formation contains abundant, diverse and well-preserved bedding-plane

assemblages of trace fossils. The Clinch Formation (and particularly more distal portions of the

Poor Valley Ridge Sandstone Member, which were examined as part of this study) is interpreted

to record transgressional deposition as part of a prograding clastic wedge in a storm-dominated

shoreface setting, under conditions of glacioeustatic sea level rise and/or compression-mediated

subsidence in the Appalachian foreland basin30,32. Measured intervals of the Clinch Formation

are characterised by 30% mm-scale, 9% mm- to cm-scale, 33% cm-scale, 22% cm- to dm-scale

and 7% dm-scale bedding.



Rockwood Formation—The Lower Silurian (Llandoverian) Rockwood Formation (Appalachian

Basin, eastern USA) is characterised by cm-scale (rarely dm-scale) fine-grained sandstone beds

interbedded with mm- to cm-scale siltstone beds, organized as packages of thicker sandstone

beds with siltstone interbeds or siltstone-dominated packages with sandy interbeds

(Supplementary Fig. 24; see end of Supplement). Sandstone beds are commonly lenticular and

planar-based and rarely ripple-topped. Rare thicker sandstone beds may be channelized and

cross-bedded. Pot casts, gutter casts and tool marks are common along bed bases, as are diverse

and well-preserved trace fossil assemblages. The Rockwood Formation is interpreted to have

been deposited in a storm-dominated mid- to outer-shelf setting as part of the post-glacial and

syn-tectonic subsidence-mediated transgressional sequence of which the upper Tuscarora, Rose

Hill and Clinch formations are also part30,32. Measured intervals of the Rockwood Formation are

characterised by 28% mm-scale, 25% mm- to cm-scale, 34% cm-scale and 14% cm- to dm-scale

bedding.

Rose Hill Formation—The Lower Silurian (Llandoverian) Rose Hill Formation (Appalachian

Basin, eastern USA) is characterised by cm-scale fine-grained sandstone beds interbedded with

mm-scale mudstone and siltstone beds (Supplementary Fig. 25; see end of Supplement).

Siltstone and thinner sandstone beds are planar; thicker sandstone beds are hematitic and not

uncommonly symmetrical ripple-topped. The Rose Hill Formation contains abundant, diverse

and well-preserved bedding-plane assemblages of trace fossils, as well as rare brachiopod and

pelycopod pavements. The Rose Hill Formation is deposited at the base of what is interpreted to

be a transgressive systems tract associated with eustatic sea level rise31,32. Measured intervals of



the Rose Hill Formation are characterised by 49% mm-scale, 6% mm- to cm-scale, 29% cm-

scale and 17% cm- to dm-scale bedding.

Mifflintown Formation—The Lower–Upper Silurian (Llandoverian–Ludlovian) Mifflintown

Formation (Appalachian Basin, eastern USA) is characterised by very fine- to fine-grained cm-

scale sandstones interbedded with cm-scale packages of mm-scale siltstone beds, with rare dm-

scale sandstone interbeds separated by silty veneers (Supplementary Fig. 26; see end of

Supplement). Thicker sandstone beds are characterised by planar lamination and symmetrically

rippled tops. Body fossils characteristic of early- to mid-Palaeozoic normal marine faunas—

including ostracods, brachiopods, ramose byrozoans, crinoids and pelycopod bivalves—are

common as either shell hash lenses, concretionary lags or wackestone or packstone bioclastic

horizons. Dense, diverse and well-preserved trace fossil assemblages are also common along bed

junctions. The Mifflintown Formation is interpreted to represent storm-mediated deposition

along a deepening ramp, with facies variability driven largely by eustatic, rather than tectonic

variation33. Measured intervals of the Mifflintown Formation are characterised by 39% mm-

scale, 1% mm- to cm-scale, 33% cm-scale, 15% cm- to dm-scale and 12% dm-scale bedding.

Red Mountain Formation—The Lower–Upper Silurian (Llandoverian–Pridolian) Red Mountain

Formation (Appalachian Basin, eastern USA) is characterised by thinly interbedded cm- to dm-

scale, very fine- to fine-grained sandstones, mm- to cm-scale siltstones and rare thin-bedded,

sandy bioclastic (wackestone to packstone) carbonates and ironstone beds (Supplementary Fig.

27; see end of Supplement). This study includes the Taylor Ridge, Duck Springs and

Birmingham members. Strata of the Red Mountain Formation occur either as siltstone-dominated



packages containing thin sandstone interbeds or as thicker-bedded sandstone packages

containing siltstone interbeds or silty partings. Thicker sandstones not uncommonly contain low-

angle cross-laminae and may have channelized bases; tool marks and groove casts are also not

uncommon along sandstone bed bases. Sandstone beds commonly pinch and swell laterally;

planar sandstone bed bases and wavy to rippled bed tops are common. Both coarsening

(shallowing) and fining (deepening) upward sequences are common, reflecting variation in the

balance between accommodation space, subsidence rates and sea level change. Body fossils

characteristic of early- to mid-Palaeozoic normal marine faunas—including brachiopods,

crinoids, ramose bryozoans and rugose and tabulate corals—are common and occur either as

bioclastic stringers, lenses or wackestones (ranging from disarticulated and fragmented sclerites

to complete specimens), or as isolated molds within sandstone beds. Dense, diverse and well-

preserved trace fossil assemblages are also common along bed junctions. The examined facies of

the Red Mountain Formation are interpreted to represent deposition along a storm-dominated

shelf, ranging from “inner shelf” (between normal and storm wavebase) and “outer shelf” (near

storm wavebase) and characterised by variable siliciclastic sediment input34. Measured intervals

of the Red Mountain Formation are characterised by 35% mm-scale, 22% cm-scale, 26% cm- to

dm-scale and 16% dm-scale bedding.

Herkimer Formation—The Joslin Hill Member of the Middle Silurian (Wenlockian) Herkimer

Formation (Appalachian Basin, eastern USA) is characterised by interbedded shale and fine- to

medium-grained cm-scale dolomitic sandstones, packaged as a coarsening (shallowing) upward

sequence. Sedimentary structures consist primarily of symmetrical ripples and locally abundant

tool marks; sandstones in the upper portion of the studied interval are also characterised by low-



angle cross-lamination. The Joslin Hill Member contains dense, diverse and well-preserved trace

fossil assemblages, which are dominated by Rusophycus-Palaeophycus composite trace fossils

which have been interpreted as “hunting burrows” recording predatory interactions between

trilobites and the Palaeophycus tracemaker. Due to the predominance of mud and erosive

sedimentary structures, the Joslin Hill Member is interpreted to have been deposited in a shallow

shelfal environment between normal and storm wavebase in the Appalachian foreland basin35.

Bloomsburg Formation—The Moyer Ridge Member of the Middle–Upper Silurian (Ludlovian–

Pridolian) Bloomsburg Formation (Appalachian Basin, eastern USA) is characterised by thin

packages of cm-scale fine-grained sandstone interbedded with siltstones. Sandstone beds are

commonly planar-based and rarely rippled. The Moyer Ridge Member contains dense and likely

mono-ichnospecific assemblages of intergradational Rusophycus and Cruziana, which appear to

commonly be paleocurrent-aligned. These fossiliferous beds are interpreted to have been

deposited in low-energy nearshore shallow marine settings, ranging from intertidal to marginal

marine36.

Criteria for Assessment of Intensity of Sediment Mixing

1) Bedding thickness: The thickness of beds separated by clear bed junctions indicates the

maximum depth to which bioturbation penetrated without having disrupted the coherency

of individual beds. Bed junctions will be erased by intensive and deep burrowing;

sediment deposited as thin event beds will be homogenized and merged into thicker beds

(cf. ref. 6). In contrast, thin event beds preserved in a stratigraphic succession imply

relatively reduced infaunal reworking intensities. Bedding thickness was assessed on the



individual bed scale (absolute thickness, measured for each individual, discrete bed) over

representative, 50 cm- or 100 cm-thick ‘microstratigraphic sections.’ Additionally,

bedding thickness was assessed on the package scale (approximate thickness of beds,

demarcated as mm-scale [1–10 mm], cm-scale [1–10 cm], dm-scale [1–10 dm] or m-scale

[≥1 m], determined for individual lithologically distinct facies packages over each one-

meter stratigraphic interval) for each stratigraphic section (tens to hundreds of meters).

2) Fabric disruption: Biogenic fabric disruption constitutes another parameter for

measurement of the extent to which burrowing organisms have disrupted the stratigraphic

expression of original depositional (physical) fabrics. The Ichnofabric Index (ii) of

Droser and Bottjer37 schematically demarcates the intensity of infaunal disruption of

sedimentary fabrics (i.e., extent of preservation of primary physical sedimentary

structures) into six indices, ranging from ii 1 (laminated) to ii 2 (discrete but isolated

burrows, up to 10% of depositional fabric disrupted), ii 3 (both isolated and locally

overlapping burrows, approximately 10-40% of depositional fabric disrupted), ii 4 (last

vestiges of depositional fabric preserved, approximately 40-60% of depositional fabric

disrupted), ii 5 (no vestige of depositional fabric, but discrete burrows still visible) and ii

6 (completely homogenized—neither depositional fabric nor discrete burrows are

preserved). The Ichnofabric Index provides a useful and efficient metric for both field

(particularly where stratigraphic exposure is greater than bedding-plane exposure) and

laboratory assessment of infaunal mixing intensity. Ichnofabric Index was measured

throughout field exposures, wherever possible, as well as for selected hand samples,

which were collected at regular (m-scale) intervals from each distinct facies package, cut,

polished and scanned. For each hand sample, maximum Ichnofabric Index (irrespective



of scale) and average (‘whole-rock’) Ichnofabric Index were measured. Average

Ichnofabric Indices were measured in order to provide scale normalization (e.g., a 1 cm2

zone of ii 6, although a valid maximum Ichnofabric Index, is not necessarily

representative of a bed or stratigraphic interval). In this regard, maximum Ichnofabric

Indices are illustrative as to infaunal behaviour, whereas average (‘whole-rock’)

Ichnofabric Indices are better metrics of the extent of sediment mixing. Subsequently, the

mean of individual average Ichnofabric Index measurements was calculated for each time

interval in order to measure shifts in the range of variability characteristic of each time

interval.

3) Depth of bioturbation: The depth of discrete burrows, particularly where contact with the

ancient sediment-water interface can be clearly determined, indicates the maximum depth

of the zone of infaunal activity (i.e., the infaunal ‘habitable zone’). This, in turn, provides

information concerning the morphological and physiological ability of animals to

penetrate the substrate. Maximum burrow depth was noted, wherever possible, over each

stratigraphic interval.

4) Bioglyphic preservation: The fidelity of preservation of shallowly emplaced trace fossils

is a direct metric of substrate consistency; soupy, well-mixed sediment will not capture

the same level of detail as a firm and undisturbed substrate. The preservation of

bioglyphs—finely-preserved burrow ornamentation or other organismal “fingerprints”

such as scratch marks38—is a particularly useful indicator of exceptional preservation and

thus a firm (i.e., unmixed) substrate at the depth of emplacement. When coupled with

data documenting depth of bioturbation, trace fossil preservation can provide information

on substrate conditions at a reliably estimated distance from the ancient sediment-water



interface and thus an approximate depth of the mixed layer. The presence or absence of

bioglyphic preservation was noted throughout all measured stratigraphic successions.

5) Palaeobiological and palaeoecological complexity: The morphological and assemblage-

level complexity of shallowly emplaced trace fossils, including trace fossil size, density,

diversity and taphonomy are important metrics of the extent and character of substrate

colonization, as well as of infaunal behavioural complexity. The preservation of open

burrows, such as Treptichnus, Gyrolithes, Monocraterion (e.g. ref. 2, 39–40) indicates

that shallow sediment was cohesive and unmixed, whereas truncated burrows and infill

by foreign material suggest intensive and multi-generational substrate colonization and

sediment mobilization41. Additionally, the Bedding Plane Bioturbation Index (BPBI) of

Miller and Smail42, which demarcates burrowed bed surfaces according to the density of

surface coverage and disruption (from BPBI 1 [0% disruption] to BPBI 5 [60–100%

disruption]), was used to characterise the extent of infaunal colonization of bedding plane

exposures. Cross-cutting and consistent tiering relationships were further used to quantify

maximum depth of bioturbation41,43.

6) Surficially produced physical sedimentary structures: Like surficially and shallowly

produced trace fossils, surficially produced physical sedimentary structures, such as tool

marks are particularly informative metrics of substrate consistency and the depth of

sediment mixing (e.g., ref. 44). Sedimentologists have long noted that “hydroplastic” or

cohesive sediment is required for the formation and preservation of tool and flute

marks44. Well-preserved and fine-scale tool marks are therefore especially suggestive of

cohesive (unmixed) sediment at the sediment-water interface and, in conjunction with

conformable bed junctions, suggest limited erosion and near-complete preservation of the



palaeo-sediment water interface. Tool marks and similar features were noted as “absent,”

“present/rare,” “common” or “abundant” for all available basal bedding plane exposures.

Assessment of Early Palaeozoic L

All of the criteria discussed above (bed thickness, frequency of occurrence of surficial

sedimentary structures, burrow depth, fidelity of preservation and frequency of occurrence of

bioglyphs, Ichnofabric Index and trace fossil morphology, dimensions and architectural

complexity) were used to determine an average mixed layer depth (L) for each of the three

temporal intervals. Bed thickness (Main Text Fig. 2) and Ichnofabric Index (Main Text Fig. 3)

were given the greatest weight, on grounds that these are quantitative criteria that directly reflect

sediment properties, with significant input from the other criteria. Data from middle Palaeozoic

(Devonian–Carboniferous) successions were not collected as part of this study (nor does a

middle Palaeozoic bioturbation dataset, comparable to that presented here for the lower

Palaeozoic, exist). However, for purposes of modelling marine [SO4] using our bioturbation-

dependent sulphate model, a Devonian L was estimated on the basis of previously reported body

fossil, trace fossil and sedimentological evidence. In the absence of stratigraphically-grounded,

facies-specific bioturbation data, 125% and 50% of the estimated Devonian L were used in lieu

of maximum and minimum L values, respectively, for purposes of conducting model sensitivity

tests (e.g., see Lmin and Lmax curves in Main Text Fig. 4a).

Data used to estimate early Palaeozoic L values (in cm) were based on a combination of

quantitative, semi-quantitative and descriptive data. Therefore, although there is no formulaic

calculation of L, our L estimates are tied directly to the presented empirical dataset. Justification



for L estimates for each time interval are given below. Macrostratigraphic (all lithologies; intra-

facies package quantification of the proportion of mm-, mm- to cm-, cm-, cm- to dm-, dm-, dm-

to m- and m-scale bedding within each stratigraphic metre) and microstratigraphic (precise [to

the 0.1–1 cm] measurement of all sandstone event beds within a given stratigraphic interval)

thickness, and cumulative frequency distributions (in 0.10-1.0 cm bins), mean thickness and

median thickness of microstratigraphic event beds were given the greatest weight. Typically the

15-20% and 50% cumulative frequency distributions of microstratigraphic event bed thicknesses

were used as a first approximation of minimum and maximum L values, respectively, for each

temporal interval. However, particularly since, although bioturbation sets a lower threshold for

minimum event bed thickness, depositional energy dynamics may, in the early Palaeozoic, have

played a larger role than bioturbation in controlling maximum event bed thickness, other

bioturbation metrics (e.g., Ichnofabric Index, burrow depth and tier, the frequency of tool mark

and bioglyph preservation and minimum, mean and maximum trace fossil dimensions) were used

to refine (increase or decrease) these minimum and maximum estimates, as well as to estimate an

average L value for each temporal interval.

Lower–middle Cambrian macrostratigraphic bed thicknesses are, on average, mm- to cm-scale.

For the lower–middle Cambrian, cumulative frequency distributions indicate that >50% of

sandstone beds are <0.5 cm and that >30% are <0.2 cm thick. Moreover, almost 20% of

sandstone beds are <0.1 cm in thickness. Median sandstone bed thickness is <0.5 cm; mean

sandstone bed thickness is 1.3 cm. Ichnofabric analysis reveals an almost complete lack of well-

mixed beds (mean ii of 2.1), and zones of hand samples, beds and even entire stratigraphic

intervals characterised by ii 1 are common. Burrows are typically sub-mm-scale in diameter and



depth. These data, coupled with the high abundance of surficially-produced trace fossils, the high

frequency of bioglyphic preservation and the high abundance of mm-scale tool marks (mm-scale

length, sub-mm-scale width and depth; suggesting firmground conditions within 0.1 cm of the

palaeo-sediment-water interface) indicate that the lower–middle Cambrian mixed layer could not

have exceeded 0.5 cm and may have been as thin as <0.1 cm. Within this range, due to the

preponderance of surficial, sub-mm- to mm-scale tool marks; bioglyphic, cryptobioturbational,

bedding plane-parallel trace fossils; and the high frequency of event beds of <0.2 cm, we

approximated an average lower–middle Cambrian L of 0.2 cm, with a maximum and minimum L

of 0.5 cm and <0.1 cm, respectively.

Cambro-Ordovician heterolithic, shelfal strata are also characterised by mm- and mm- to cm-

scale macrostratigraphic bed thicknesses. Median sandstone bed thickness is 2.5 cm; mean

sandstone bed thickness is 3.4 cm. Cumulative frequency distributions indicate that >65%

sandstone beds are <3 cm, >55% are ≤2.5 cm, >40% are ≤2 cm and nearly 20% are <1 cm (with

5% ≤0.5 cm). However, these slightly higher values for event bed thickness are counterbalanced

by the common occurrence of cryptobioturbation-scale (burrow diameter <0.1 cm) trace fossils

(even intensively burrowed fabrics are characterised by cryptobioturbation-scale structures and

are limited to the mm- to cm-scale) and low mean ii of 2.4. Likewise, the common occurrence of

small (mm- to cm-scale length, sub-mm- to mm-scale width and depth) tool marks and bioglyphs

indicate firmground conditions within millimetres of the palaeo-sediment-water interface. These

observations indicate that Cambro-Ordovician mixed layer depth could not have exceeded 2.5

cm (maximum L) and may have been as low as 0.5 cm (minimum L), and indicate an average

Cambro-Ordovician mixed layer depth of 1 cm.



Ordovician–Silurian heterolithic successions are characterised by a very similar or potentially

(albeit not significantly) slightly thinner scale of bedding to Cambro-Ordovician successions:

median sandstone bed thickness is 1.6 cm; mean sandstone bed thickness is 3.1 cm; 15%

sandstone beds are <0.5 cm, >35% are <1 cm, >55% are <2 cm, >70% are <3 cm). Ordovician–

Silurian successions are likewise characterised by similar average intensities of fabric disruption

(mean ii = 2.8), preponderance of cryptobioturbation, common occurrence of mm-scale tool

marks and common occurrence of bioglyphs to Cambro-Ordovician strata, indicating a similar

range in probable mixed layer depths (minimum L of 0.5 cm; maximum L of 2.5 cm). However,

zones of higher ii, albeit rare, are more common in Ordovician–Silurian than in Cambro-

Ordovician successions which, coupled with the relatively greater frequency of relatively large,

deep, cm- to dm-scale burrows characteristic of Ordovician–Silurian successions, indicates a

slightly greater average mixed layer depth, approximated as 1.5 cm.

Independent lines of evidence, derived from the body fossil record of immobile muddy substrate-

dwelling suspension feeding taxa7, infaunal tiering depths45, tempestite bed thicknesses46 and the

reworking rates of modern bulldozing taxa7,47, suggest that a major radiation of bulldozing taxa

began in the Devonian, later followed by major Mesozoic increases in reworking depth and

intensity47–48 in conjunction with the Mesozoic Marine Revolution. Although this hypothesized

Devonian radiation of bulldozing taxa has yet to be tested through detailed and systematic

examination of the Devonian stratigraphic record of sediment mixing (i.e. assessment of whether

the Devonian stratigraphic record is indeed characterised by a major expansion in the efficiency

and extent of sediment mixing, indicating a radiation in mobile deposit-feeding), on the basis of



the currently available body fossil, trace fossil and sedimentary evidence we have, for purposes

of modelling secular changes in [SO4], predicted a Devonian L of 3 cm. Due to the absence of

stratigraphically-grounded, facies-specific, globally representative bioturbation data that could be

used to more directly approximate minimum and maximum L values, 125% and 50% of the

estimated Devonian L were used in lieu of maximum and minimum L values, respectively, for

purposes of conducting model sensitivity tests (e.g., Main Text Fig. 4).

Sulphur Mass Balance and Model Parameters

The model we employ builds from a previously developed bioturbation-dependent global sulphur

mass balance model19 (see Supplementary Table 1 for list of parameters), in which marine

sulphate concentrations will vary as a response to marine sulphur input and burial fluxes:

d[SO4]

dt=Fluxin-Fluxout (1),

The balance between riverine delivery (Fluxin) and burial (Fluxout) of sulphur, as either sulphide,

primarily pyrite (FeS2) or sulphate, primarily gypsum (CaSO4·5H2O) evaporites, can be

estimated from a mass balance that utilizes the geologic record of sulphide and sulphate δ34S

values:

fpyr = (δ34Sinput – δ34Ssulphate)/(δ34Ssulphide – δ34Ssulphate) (SI 1),

where fpyr is equivalent to the proportion of total sulphur buried as sulphide and is dependent

upon the isotopic composition of sulphur delivered to the ocean and that of sulphur buried as



either sulphide or sulphate. Like Canfield and Farquhar19, we employed this equation to calculate

fpyr values for the lower and middle Palaeozoic, using previously published δ34Ssulphide and

δ34Ssulphate databases (e.g., ref. 49–50; see Supplementary Table 2) and assuming a constant input

flux19, 49–50. However, we also explored sensitivity of the model to various proposed input flux

values and considered invariant fpyr values (e.g. ref. 51; Supplementary Fig. 3c–d, 4–5).

Supplementary Table 1. Model input parameters.

Parameter Magnitude

Sulphur input rate (Fin) 3.3 x 1012 mol∙yr-1

Modern sulphate reduction rate (SR) 11.3 x 1012 mol∙yr-1

Modern pyrite burial rate (x∙SR) 1.2 x 1012 mol∙yr-1

Modern x 0.106

Modern [SO4] 28 mM

Modern sulphate reservoir 3.8 x 1019 mol

Isotopic composition of S input (δ34Sin) 5‰

Ocean volume (Vo) 1.36 x 1021 L

Pre-bioturbation x 1

Pre-bioturbation [SO4] 5 mM

Pre-bioturbation SR 3.1 x 1012 mol∙yr-1

aOC 9.28 x 1011

y 0.75

Model start time 542 Ma

Time-step duration (T) 3 x 105 yr

Palaeozoic x (initial, LMC, CO, OS, D) 1, 0.801, 0.656, 0.579, 0.398

Total burial of sulphur, Fluxout is the sum of the burial fluxes of pyrite and evaporite:

Fluxout = x∙SR + evap (SI 2),

where SR is the globally integrated sulphate reduction rate, x is the stoichiometric proportion of

sulphide buried as pyrite from sulphide produced through bacterial sulphate reduction and evap



is the rate of sulphur burial as evaporites. Since fpyr reflects not only the S isotope mass balance

but also the mass balance of S fluxes, evap can be placed in the context of fpyr:

fpyr = xSR∙(xSR + evap)-1 (SI 3)

which can be rearranged to:

evap = xSR∙(fpyr)-1 – xSR (SI 4)

Therefore, the total sulphur burial flux can be considered in terms of x, SR and fpyr:

Fluxout=x∙SRt-1

fpyr

(2).

Supplementary Table 2. Time-binned sulphur isotope (δ34S) data used to calculate fpyr. Values from ref.

50.

Time Interval (Ma) δ34Spyrite (‰) δ34Ssulphate (‰)

542–530 4.25 30.18

530–510 3.76 33.36

510–490 4.08 35.30

490–470 0.72 30.48

470–450 -2.52 25.90

450–430 -4.76 27.06

430–410 -5.60 26.04

410–390 -7.38 21.84

390–370 -8.92 20.90

370–359 -10.22 19.06

An initial sulphate reduction rate can be calculated using the following equation:



SR = aOC[SO4]y (SI 5),

where a is a proportionality constant, OC represents the availability of reactive carbon for

sulphate reduction and y is an exponential factor scaling SR to [SO4]. Similarly to previous

studies19, we calibrated this equation using modern values for [SO4] (28 mM) and estimates for

modern SR (ranging from 11.3 x 1012 mol∙yr-1 [ref. 52] to 40 x 1012 mol∙yr-1 [ref. 53]) and

explored various values of y within the range of 0.3 to 0.75. Iterations run with varying y and

aOC indicate that the model is not strongly sensitive to variations in y relative to variations in

aOC (Supplementary Fig. 3e, 5). Using the modern values of [SO4] = 28 mM, SR = 11.3 x 1012

mol∙yr-1 and y = 0.75, we solved for aOC = 0.93 x 1012. Various initial (latest Neoproterozoic

and earliest Cambrian) [SO4] values54–56 were explored within the probable range of 1–10 mM;

the model is relatively insensitive to variation in initial [SO4], within this range (Supplementary

Fig. 3b).

We incorporated the impact of bioturbation upon marine sulphate concentrations by utilizing the

term x, the stoichiometric proportion of sulphide buried as pyrite from sulphide produced

through bacterial sulphate reduction. Using data from a range of modern marine localities19,57–64,

the relationship between mixed layer depth, L (and, in one case, ii) and x was calibrated

(Supplementary Fig. 2). For the one case for which modern ii and not L had been reported

(Georgia Bight; ref. 64), ii was normalized to L on the assumption that the maximum observed

shelfal marine L of ~15 cm correlated approximately to the maximum ii of 6. The resulting

calibration between x and L was found to have a strong exponential fit (r2 = 0.9143;

Supplementary Fig. 2, Supplementary Table 3):



x = 0.84183∙e-0.25L (3)

Supplementary Figure 2. Relationship between the stoichiometric proportion of sulphide buried as

pyrite from sulphide produced through bacterial sulphate reduction (x) and mixed layer depth (L) from a

range of modern marine shelfal localities. Data from Long Island Sound (FOAM57–58, NWC58–59,

Sachem58), Cape Lookout Bight60–61, Georgia Bight63–64 and global average compilations19,52,62. This

relationship can be expressed exponentially, as x = 0.84183∙e-0.25L (Eq. SI 3; r2 = 0.9143). Black line

denotes best-fit curve; grey lines denote upper- and lower-boundary exponential curves (constraining

highest and lowest y-intercept values, respectively).

Palaeozoic values for L were calculated from the suite of mixing intensity data discussed above.

Using Eq. 3, we calculated Palaeozoic x values. Each temporal interval (lower–middle Cambrian,

Cambro-Ordovician and Ordovician–Silurian) was assigned an x value. Additionally, a predicted

Devonian x value was calculated on the basis of evidence from the body fossil and sedimentary

records (see above discussion)7,45–48. Given the small size of the modern x-L database, we ran

additional tests to assess the sensitivity of the model to the fit of the modern x-L curve



(Supplementary Fig. 3g). These tests demonstrate that the model is not strongly sensitive to

variation in the fit of this curve and that the trend indicated by the existing data is robust.

Supplementary Table 3. Modern marine shelfal x and L values, with reported standard deviations (sd)

and analytical error.

Locality L (cm) L error (cm) x x error (%) Ref.

LIS-FOAM 8.0 ±4.0 0.15 ±10 51-52

LIS-NWC 13.0 ±3.0 0.06 ±10 52-53

LIS-Sachem 0 ±0.5 0.75 ±10 52

Cape Lookout Bight 0 ±0.5 0.77 ±19 54-55

Georgia Bight 13.9 - 0.017 - 57-58

Modern Global Average 9.8 ±4.5 sd 0.033 - 19, 56

Modern Global Average 9.8 ±4.5 sd 0.11 - 46, 56

Hypothetical Pre-Bioturbation 0 - 1.0 - 19

We solved for marine sulphate concentrations using the Euler method, with a time step of

300,000 years and a constant marine reservoir volume. We modelled the cumulative growth of

the sulphate reservoir over the approximately 180 million-year interval encompassing the early

and middle Palaeozoic (Cambrian–Devonian). Varying the time-step duration did not appear to

have any significant effect upon model outputs. At steady state, the model can also be expressed

as:

[SO4] = ((δ

34

Sinput

– δ34

Ssulphate

)∙Fluxin∙e0.25L

(δ34

Ssulphide

– δ34

Ssulphate

)∙0.84183∙aOC)

1/y

(SI 6)



Supplementary Figure 3.

Sensitivity tests of bioturbation-

mediated [SO4] model. Iterations

of the model were run with both

Palaeozoic (stratigraphic) and

modern x values (a), and while

varying: initial [SO4] (b), fpyr (c),

δ34Sin (d), aOC and y (e), Fluxin

(f) and the exponential

relationship between x and L (g)

in order to test the sensitivity of

the model to these parameters.

Solid black curve denotes

baseline conditions (preferred

model parameters). Unless

otherwise stated, all model

iterations were run with the

parameters of a 542 Ma start

time; initial [SO4] of 5 mM;

time-step of 300 kyr; aOC =

9.2835 x 1011; y = 0.75; modern-

level Fluxin of 3.3 x 1012 mol/yr;

geologically varying x, as

calculated from the stratigraphic

record of L, using Eq. 3; and

geologically varying fpyr

calculated from the δ34Ssulph and

δ34Spyr records (ref. 49–50) and

δ34Sin of 5‰. Note log scale for

[SO4] values in (a).



Supplementary Figure 4. Sensitivity analysis of the relationship between L and steady-state outputs of

the bioturbation-dependent [SO4] model. Iterations of the model were run at five distinct values of L

(representing early–middle Cambrian, Cambro-Ordovician, Ordovician–Silurian, Devonian and modern

levels of sediment mixing intensity), held constant throughout the model, and with constant fpyr (0.8).

Model iterations were run with a range of Fluxin magnitudes and aOC values. Solid black curve denotes

baseline conditions (preferred model parameters). Unless otherwise stated, all tests were run with the

parameters of aOC = 9.2835 x 1011; y = 0.75; modern-level Fluxin of 3.3 x 1012 mol/yr; and x values

calculated from L (see Supplementary Table 1). Note log scale for [SO4] values.

Sulphur Mass Balance Model Results and Implications for the Evolution of Biogeochemical

Cycling

Our reference model is based on our new stratigraphic mixing intensity data and what we feel are

the most reasonable previously estimated sulphur cycle parameters (e.g., ref. 19, 49, 52). In our

reference model, the [SO4] curve is static throughout the early and middle Palaeozoic. This trend

is robust given a range of reasonable estimates for sulphur cycle parameters (See Supplementary

Fig. 3–5 for a full range of model sensitivity tests). Conversely, as discussed in the main text,

model iterations run with modern-level mixing intensities (Supplementary Fig. 3a, 4–5) result in

unreasonably high marine sulphate concentrations.



Supplementary Figure 5. Time-dependent sensitivity

tests of the impact of L upon

outputs of the bioturbation-

dependent [SO4] model.

Iterations of the model were

run at five distinct values of

L (representing early–middle

Cambrian, Cambro-

Ordovician, Ordovician–

Silurian, Devonian and

modern levels of sediment

mixing intensity), held

constant throughout the

model, and with constant fpyr

(0.8). Model iterations were

run with a range of Fluxin

magnitudes (a–c) and aOC

and y values (a, d–g) until

steady-state conditions were

achieved (with the exception

of g, within the first 100 myr

and commonly sooner).

Unless otherwise stated, all

tests were run with the

parameters of a 542 Ma start

time, initial [SO4] of 5 mM;

time-step of 300 kyr; aOC =

9.2835 x 1011 and y = 0.75;

modern-level Fluxin of 3.3 x

1012 mol/yr; and x values

calculated from L (see

Supplementary Table 1).

Note log scale for [SO4]

values.



The sulphate concentration stasis observed in the reference model is a reflection of decreased

pyrite burial (a drop in fpyr) and a corresponding increase in gypsum burial, with the backdrop of

a constant input flux to the oceans. Increased bioturbation is associated with decreased pyrite

burial (decreasing x values). However, concurrent increases in marine evaporite burial, as

estimated from the fpyr record, result in static [SO4] values in close agreement with independent

geologic constraints (cf. ref. 54–56). This switching in the balance of sinks is driven by increased

bioturbation (decreasing x values). Although the model was run with a constant sulphur input

flux, this observation holds true for a range of magnitudes for the sulphur input flux (see

Supplementary Fig. 3f, 4–5). We think there is strong evidence for decreasing fpyr values through

the Palaeozoic (e.g., ref. 19, 65). However, we also explored using near-constant Palaeozoic fpyr

values (Supplementary Fig. 3c, 4–5)—these latter iterations resulted in increasing and higher

[SO4] not in agreement with estimates provided by the fluid-inclusion and modelled CAS

records54–56. It is interesting to note that relatively high [SO4] values (>20 mM) for the Ediacaran

have been suggested on the basis of fluid-inclusion data from the Ara evaporites of Oman55,

which contrasts with the relatively low (<10 mM) levels observed through the early

Palaeozoic19,54–56. These results may suggest that, during the Precambrian, it was possible to have

significant growth of the marine sulphate reservoir without significant bioturbation. However,

the values suggested by the Ara evaporites still need to be confirmed and supported with

additional work, given that they conflict with the generally held view that Precambrian marine

sulphate concentrations were low19. It was recently suggested that during the late Cambrian

marine sulphate concentrations were lower than previously proposed66. Specifically, Gill et al.

(ref. 66) suggested, on the basis of the modelled recovery of sulphate sulphur isotopes following

the Steptoean Positive Carbon Isotope Excursion (SPICE), that seawater sulphate preceding the



SPICE was < 2.5 mM, which is at the lower end of the range suggested from previous lower

Palaeozoic work. However, this recent suggestion that does not affect our central conclusions; if

sulphate was low during the late Cambrian, this only provides additional support for very limited

bioturbation during this time interval.

In sum, a strong case can be made that the Palaeozoic was characterised by low sulphate

concentrations and high fpyr values relative to the modern oceans. Based on the presented

modelling work coupled to our ichnological and sedimentological stratigraphic records of

sediment mixing, we propose that bioturbation remained limited through the early Palaeozoic,

keeping sulphide reoxidation low. Lower extents of sulphide reoxidation were likely a key

reason that early Palaeozoic marine sulphate concentrations were much lower than in the

modern. The strong sensitivity of sulphate concentration to x values, relative to all other

parameters (Supplementary Fig. 3a, 4–5), implies that, although tectonic controls will of course

influence sulphur delivery to and thus sulphate concentrations in the marine reservoir,

bioturbation intensities exercise the strongest influence upon marine sulphate concentrations.

Stratigraphic, paleontological and ichnological evidence indicate that it was likely not until the

late Palaeozoic and early–mid Mesozoic that bioturbation intensities were high enough to have

increased sulphide reoxidation rates sufficiently to outpace gypsum deposition and allow

significant levels of dissolved sulphate to accumulate in the ocean.

Effects of Bioturbation on Atmospheric Oxygen Levels

Bioturbation may have also influenced Palaeozoic fluctuations in the carbon cycle and

atmospheric oxygen level. Although certain burrowing behaviours, such as reverse-conveyor



burrowing, involve transport of sediment from the sediment-water interface to deep within the

sediment pile and thus increase carbon burial, these are outweighed in importance by sediment

mixing which, particularly in modern marine settings, dramatically increases sediment porosity

and thus the remineralization of organic carbon58, ultimately decreasing carbon burial. Therefore,

particularly on long time scales, major increases in the intensity of bioturbation can be expected

to lead to decreases in reductant burial and thus atmospheric oxygen.

Given the ability of bioturbation to influence organic carbon and sulphide burial, it follows that

major increases in bioturbation intensity could change atmospheric oxygen concentrations. This

basic conclusion is likely valid regardless of the effects of bioturbation on marine phosphorus

burial (cf. ref. 67). Boyle et al.67 recently proposed that increased bioturbation in the early

Cambrian caused a decrease in atmospheric oxygen levels—and supported this model with Mo

and U enrichment data suggesting ocean deoxygenation. This appears to clash with our evidence

for limited burrowing throughout the early Palaeozoic. However, additional work is needed to

better gauge the sensitivity of C-P cycling to minor increases in mixing intensity—given that

there is likely a measurable, albeit minor (~0.2 cm), increase in mixed layer depth through the

early–middle Cambrian. In contrast, a dramatic increase in bioturbation intensity in the

Devonian—with the onset of extensive mobile deposit feeding—should, by decreasing organic

and sulphide carbon burial, have caused a drop in atmospheric oxygen. This major bioturbation

radiation event, as predicted from the body fossil record7,47, could cause an early and mid-

Devonian decline in surface oxygen levels—which, interestingly, is predicted by Berner’s

GEOCARBSULF model of Phanerozoic atmospheric oxygen levels from global carbon and

sulphur isotope records68. In contrast, Mo and U enrichments and isotope values in marine



sediments track the marine redox landscape which, although heavily influenced by atmospheric

oxygen concentrations, is also controlled by the strength and operation of the biological pump

(e.g., particulate packaging). Therefore, although oxygen levels in the early Palaeozoic are

poorly constrained and were likely characterised by high variability, we find that current

paleontological, stratigraphic and geochemical constraints, as well as the data presented herein,

provide stronger support for a significant and bioturbation-mediated drop in atmospheric oxygen

levels in the early Devonian than for a bioturbation-mediated middle Cambrian drop. Subsequent

radiations in land plant abundance and diversity, particularly in the late Palaeozoic (mid-

Devonian, Carboniferous and Permian)69, likely dramatically increased organic carbon delivery

to the oceans. Specifically, the mid-late Devonian marked the rise of many early land plant

clades, as well as the first forests and the Carboniferous was marked by further development and

diversification of extensive forests with lignin-rich trees (e.g., lycopod forests)69. These changes

in land plant evolution, which are often evoked as drivers of oxygenation67, would have allowed

for extensive organic carbon burial and thus increases in atmospheric oxygen levels despite

continually increasing intensities of sediment mixing. The evolution of sediment mixing can thus

be considered to have, in part, shaped the Palaeozoic evolution of atmospheric oxygen (e.g. ref.

67). However, better quantitative constraints on the effect of sediment mixing on organic carbon

oxidation rates at varying sulphate levels could be used to refine this idea. We further hope that

the framework we have developed for investigation of the impact of the evolution of sediment

mixing on sulphur cycling can also be used, in future, to explore the impact of bioturbation upon

the carbon cycle.



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Supplementary Information for: Protracted Development of Bioturbation through the Early

Palaeozoic Era

Figure Legends for Stratigraphic Logs

Supplementary Figure 6. Stratigraphic profile of the Chapel Island Formation (Fortune Head,

Newfoundland, Canada). Macrostratigraphic (metre-scale) record of sedimentological and

palaeontological features, with microstratigraphic (bed-scale) inset of metres 10–11. Dashed lines

indicate points of correlation between sections. Along a single horizon, one sedimentological or

palaeontological symbol denotes that the feature is ‘present,’ two symbols denote that the feature is

‘common’ and three that it is ‘abundant.’ Grain sizes: mu, mud; si, silt; vf, very fine-grained sand; f,

fine-grained sand; m, medium-grained sand; c, coarse-grained sand; cgl, conglomeratic-sized particles

(granules, pebbles, cobbles). Modified from ref. 5.

Supplementary Figure 7. Stratigraphic profile of the Torreárboles Sandstone (Guadajira, Spain).

Macrostratigraphic (metre-scale) record of sedimentological and palaeontological features. Along a

single horizon, one sedimentological or palaeontological symbol denotes that the feature is ‘present,’

two symbols denote that the feature is ‘common’ and three that it is ‘abundant.’ “Burrowing

indeterminate,” abbreviated as “burrowing ind.” denotes that, within bedding-plane trace fossil

assemblages, specific ichnotaxa were not noted. Grain sizes: mu, mud; si, silt; vf, very fine-grained

sand; f, fine-grained sand; m, medium-grained sand; c, coarse-grained sand. Modified from ref. 5.

Supplementary Figure 8. Stratigraphic profile of the Poleta Formation (Lida, Nevada, USA).

Macrostratigraphic (metre-scale) record of sedimentological and palaeontological features, with

microstratigraphic (bed-scale) inset of metres 0–0.5. Dashed lines indicate points of correlation between

sections. Along a single horizon, one sedimentological or palaeontological symbol denotes that the

feature is ‘present,’ two symbols denote that the feature is ‘common’ and three that it is ‘abundant.’

“Burrowing indeterminate,” abbreviated as “burrowing ind.” denotes that, within bedding-plane trace

fossil assemblages, specific ichnotaxa were not noted. Grain sizes: mu, mud; si, silt; vf, very fine-

grained sand; f, fine-grained sand; m, medium-grained sand; c, coarse-grained sand; cgl/carb,

conglomeratic-sized particles (granules, pebbles, cobbles) or carbonate.

Supplementary Figure 9. Stratigraphic profile of the Harkless Formation (Poleta Flats, California,

USA). Macrostratigraphic (metre-scale) record of sedimentological and palaeontological features, with

microstratigraphic (bed-scale) inset of metres 1.5–1.7. Dashed lines indicate points of correlation

between sections. Along a single horizon, one sedimentological or palaeontological symbol denotes that

the feature is ‘present,’ two symbols denote that the feature is ‘common’ and three that it is ‘abundant.’



grained sand; f, fine-grained sand.

Supplementary Figure 10. Stratigraphic profile of the Pioche Formation (Frenchman Mountain,

Nevada, USA). Macrostratigraphic (metre-scale) and microstratigraphic (bed-scale) record of

sedimentological and palaeontological features. a, Macrostratigraphic section with b, microstratigraphic

inset of metres 4.5–5. c, Second macrostratigraphic section, <1 km to north of section depicted in A.

Dashed lines indicate points of correlation between sections. Along a single horizon, one

sedimentological or palaeontological symbol denotes that the feature is ‘present,’ two symbols denote

that the feature is ‘common’ and three that it is ‘abundant.’ Grain sizes: mu, mud; si, silt; vf, very fine-



grained sand; f, fine-grained sand; m, medium-grained sand; c, coarse-grained sand. Modified from ref.

5.

Supplementary Figure 11. Stratigraphic profile of the Pioche Formation (House Range, Utah, USA).

Macrostratigraphic (metre-scale) record of sedimentological and palaeontological features. a,

Macrostratigraphic section measured at the mouth of Marjum Canyon, House Range. b, Second

macrostratigraphic section, <1 km to east of section depicted in A. Dashed lines indicate points of

correlation between sections. Along a single horizon, one sedimentological or palaeontological symbol

denotes that the feature is ‘present,’ two symbols denote that the feature is ‘common’ and three that it is

‘abundant.’ “Burrowing indeterminate,” abbreviated as “burrowing ind.” denotes that, within bedding-

plane trace fossil assemblages, specific ichnotaxa were not noted. Grain sizes: mu, mud; si, silt; vf, very

fine-grained sand; f, fine-grained sand; m, medium-grained sand; c, coarse-grained sand; cgl/carb,

conglomeratic-sized particles (granules, pebbles, cobbles) or carbonate. Modified from ref. 5.

Supplementary Figure 12. Stratigraphic profile of the Pioche Formation (Pioche Mining District,

Nevada, USA). Macrostratigraphic (metre-scale) and microstratigraphic (bed-scale) record of

sedimentological and palaeontological features. a, Macrostratigraphic section measured east of Comet

Mine, Highland Range. b, Microstratigraphic inset of metres 2.5–3. c, Microstratigraphic inset of metres

28.5–29.5. d, Microstratigraphic inset of metres 54–55. Dashed lines indicate points of correlation





grained sand; f, fine-grained sand; m, medium-grained sand; c/carb, coarse-grained sand or carbonate;

cgl, conglomeratic-sized particles (granules, pebbles, cobbles). Modified from ref. 5.

Supplementary Figure 13. Stratigraphic profile of the Eagle Mountain Member of the Carrara

Formation (Death Valley National Park, California, USA). Macrostratigraphic (metre-scale) and

microstratigraphic (bed-scale) record of sedimentological and palaeontological features. A:

Macrostratigraphic section measured in Echo Canyon, Death Valley National Park. B:

Microstratigraphic inset of metres 7–8. Along a single horizon, one sedimentological or palaeontological

symbol denotes that the feature is ‘present,’ two symbols denote that the feature is ‘common’ and three

that it is ‘abundant.’ Grain sizes: mu, mud; si, silt; vf, very fine-grained sand; f, fine-grained sand; m,

medium-grained sand; c, coarse-grained sand; cgl/carb, conglomeratic-sized particles (granule, pebble,

cobble) or carbonate.

Supplementary Figure 14. Stratigraphic profile of the Beach Formation (northeastern exposure at the

Beach, Bell Island, Newfoundland, Canada). Macrostratigraphic (metre-scale) record of

sedimentological and palaeontological features, with microstratigraphic (bed-scale) inset of metres 2-3.

Along a single horizon, one sedimentological or palaeontological symbol denotes that the feature is

‘present,’ two symbols denote that the feature is ‘common’ and three that it is ‘abundant.’ Grain sizes:

mu, mud; si, silt; vf, very fine-grained sand; f, fine-grained sand; m, medium-grained sand; c, coarse-

grained sand; cgl, conglomeratic-sized particles (granule, pebble, cobble). Modified from ref. 28.

Supplementary Figure 15. Stratigraphic profile of the Beach Formation (southwestern exposure at the

Beach, Bell Island, Newfoundland, Canada). Macrostratigraphic (metre-scale) record of

sedimentological and palaeontological features, with microstratigraphic (bed-scale) inset of metres 5–6.

Along a single horizon, one sedimentological or palaeontological symbol denotes that the feature is



‘present,’ two symbols denote that the feature is ‘common’ and three that it is ‘abundant.’ Grain sizes:

mu, mud; si, silt; vf, very fine-grained sand; f, fine-grained sand.

Supplementary Figure 16. Stratigraphic profile of the Powers Steps Formation (Upper Grebes Nest

Point, Bell Island, Newfoundland, Canada). Macrostratigraphic (metre-scale) record of sedimentological

and palaeontological features, with microstratigraphic (bed-scale) inset of metres 8-9. Along a single

horizon, one sedimentological or palaeontological symbol denotes that the feature is ‘present,’ two

symbols denote that the feature is ‘common’ and three that it is ‘abundant.’ Grain sizes: mu, mud; si,

silt; vf, very fine-grained sand; f, fine-grained sand; m, medium-grained sand; c, coarse-grained sand;

cgl, conglomeratic-sized particles (granule, pebble, cobble). Modified from ref. 28.

Supplementary Figure 17. Stratigraphic profile of the Powers Steps and Scotia formations (Grebes

Nest Point, Bell Island, Newfoundland, Canada). Mesostratigraphic (centimetre-scale) record of

sedimentological and palaeontological features. Along a single horizon, one sedimentological or


‘common’ and three that it is ‘abundant.’ Grain sizes: mu, mud; si, silt; vf, very fine-grained sand; f,

fine-grained sand; m, medium-grained sand; c, coarse-grained sand; cgl, conglomeratic-sized particles

(granule, pebble, cobble).

Supplementary Figure 18. Stratigraphic profile of the Grebes Nest Formation (Grebes Nest Point, Bell

Island, Newfoundland, Canada). Macrostratigraphic (metre-scale) record of sedimentological and

palaeontological features, with microstratigraphic (bed-scale) inset of metres 1-2. Along a single

horizon, one sedimentological or palaeontological symbol denotes that the feature is ‘present,’ two

symbols denote that the feature is ‘common’ and three that it is ‘abundant.’ Grain sizes: mu, mud; si,

silt; vf, very fine-grained sand; f, fine-grained sand; m, medium-grained sand; c, coarse-grained sand;

cgl, conglomeratic-sized particles (granule, pebble, cobble). Modified from ref. 28.

Supplementary Figure 19. Stratigraphic profile of the Bynguano Formation (Mootwingee, New South

Wales, Australia). Along a single horizon, one sedimentological or palaeontological symbol denotes that


Grain sizes: mu, mud; si, silt; vf, very fine-grained sand; f, fine-grained sand; m, medium-grained sand;

c, coarse-grained sand; cgl, conglomeratic-sized particles (granule, pebble, cobble). Modified from ref.

28.

Supplementary Figure 20. Stratigraphic profile of the Juniata Formation (South Gap, Virginia, USA).


microstratigraphic (bed-scale) insets of metres 13–14 and 24–25. Dashed lines indicate points of

correlation between sections. Along a single horizon, one sedimentological or palaeontological symbol

denotes that the feature is ‘present,’ two symbols denote that the feature is ‘common’ and three that it is

‘abundant.’ “Burrowing indeterminate,” abbreviated as “burrowing ind.” denotes that, within bedding-

plane trace fossil assemblages, specific ichnotaxa were not noted. Grain sizes: mu, mud; si, silt; vf, very

fine-grained sand; f, fine-grained sand.

Supplementary Figure 21. Stratigraphic profile of the Juniata Formation (Narrows, Virginia, USA).


microstratigraphic (bed-scale) insets of metres 2.4–3.5. Dashed lines indicate points of correlation








Supplementary Figure 22. Stratigraphic profile of the Tuscarora Formation (Macedonia, Pennsylvania,


microstratigraphic (bed-scale) insets of metres 0–1. Dashed lines indicate points of correlation between





grained sand; f, fine-grained sand; m, medium-grained sand.

Supplementary Figure 23. Stratigraphic profile of the Clinch Formation (Hagan, Virginia, USA).

Macrostratigraphic (metre-scale) record of sedimentological and palaeontological features of the Poor

Valley Ridge Sandstone Member, with microstratigraphic (bed-scale) insets of metres 16–17. Dashed

lines indicate points of correlation between sections. Along a single horizon, one sedimentological or


‘common’ and three that it is ‘abundant.’ “Burrowing indeterminate,” abbreviated as “burrowing ind.”

denotes that, within bedding-plane trace fossil assemblages, specific ichnotaxa were not noted. Grain

sizes: mu, mud; si, silt; vf, very fine-grained sand; f, fine-grained sand; m, medium-grained sand; c,

coarse-grained sand; cgl/carb, conglomeratic-sized particles (granule, pebble, cobble) or carbonate.

Supplementary Figure 24. Stratigraphic profile of the Rockwood Formation (Green Gap, Tennessee,


microstratigraphic (bed-scale) insets of metres 7.2–8.2. Dashed lines indicate points of correlation






Supplementary Figure 25. Stratigraphic profile of the Rose Hill Formation (Danville, Pennsylvania,


microstratigraphic (bed-scale) insets of metres 13–14. Dashed lines indicate points of correlation





grained sand; f, fine-grained sand; m, medium-grained sand.

Supplementary Figure 26. Stratigraphic profile of the Mifflintown Formation (Danville, Pennsylvania,


microstratigraphic (bed-scale) insets of metres 61–62. Dashed lines indicate points of correlation








conglomeratic-sized particles (granule, pebble, cobble) or carbonate.

Supplementary Figure 27. Stratigraphic profile of the Red Mountain Formation (Gadsden, Alabama,

USA). Macrostratigraphic (metre-scale) record of sedimentological and palaeontological features of the

Taylor Ridge and Duck Springs members (a) and Birmingham Member (b), with microstratigraphic

(bed-scale) insets of metres 32–33 from section a. Dashed lines indicate points of correlation between






conglomeratic-sized particles (granule, pebble, cobble) or carbonate.



Supplementary Figure 6. Stratigraphic log for the lowermost Cambrian Chapel Island Formation

(Newfoundland, Canada).



Supplementary Figure 7. Stratigraphic log for the lower Cambrian Torreárboles Sandstone (Extremadura,

Spain).



Supplementary Figure 8. Stratigraphic log for the lower Cambrian Poleta Formation (western USA).

Supplementary Figure 9. Stratigraphic log for the lower Cambrian Harkless Formation (western USA).



Supplementary Figure 10. Stratigraphic log for the lower–middle Cambrian Pioche Formation (Frenchman

Mountain, western USA).



Supplementary Figure 11. Stratigraphic log for the lower–middle Cambrian Pioche Formation (House Range,

western USA).



Supplementary Figure 12. Stratigraphic log for the lower–middle Cambrian Pioche Formation (Pioche Mining

District, western USA).



Supplementary Figure 13. Stratigraphic log for the lower–middle Cambrian Carrara Formation (western USA).



Supplementary Figure 14. Stratigraphic log for the Cambro-Ordovician Beach Formation (northeastern Beach

exposure, Bell Island, Newfoundland, Canada).



Supplementary Figure 15. Stratigraphic log for the Cambro-Ordovician Beach Formation (southwestern Beach

exposure, Bell Island, Newfoundland, Canada).



Supplementary Figure 16. Stratigraphic log for the Lower–Middle Ordovician Powers Steps Formation




Supplementary Figure 17. Stratigraphic log for the Lower–Middle Ordovician Powers Steps and Scotia

formations (Newfoundland, Canada).



Supplementary Figure 18. Stratigraphic log for the Lower–Middle Ordovician Grebes Nest Point Formation




Supplementary Figure 19. Stratigraphic log for the Cambro-Ordovician Bynguano Formation (New South

Wales, Australia).



Supplementary

Figure 20. Stratigraphic log

for the Upper

Ordovician

Juniata

Formation

(South Gap,

eastern USA).



Supplementary

Figure 21. Stratigraphic log for

the Upper

Ordovician Juniata

Formation

(Narrows, eastern

USA).



Supplementary

Figure 22. Stratigraphic

log for the

Lower Silurian

Tuscarora

Formation

(eastern USA).



Supplementary


for the Lower

Silurian Clinch

Formation (eastern

USA).



Supplementary


for the Lower

Silurian

Rockwood

Formation

(eastern USA).



Supplementary Figure 25. Stratigraphic log for the Lower Silurian Rose Hill Formation (eastern USA).



Supplementary


for the Lower–

Upper Silurian

Mifflintown

Formation

(eastern USA).



Supplementary

Figure 27. Stratigraphic

log for the

Lower–Upper

Silurian Red

Mountain

Formation

(eastern USA).


doi: 10.1038/ngeo2537 protracted development of ... · supplementary information for: protracted...

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