Proceedings of theNATIONAL ACADEMY OF SCIENCES

Volume 62 * Number 3 * March 15, 1969

PROTEROZOIC E( CARVOTES FROMI EASTERN CALIFORNIA *

BY P. E. CLOUD, JR., G. R. LICARI, L. A. WRIGHT, AND B. W. TROXEL

D)IEPARTMENT OF GEOLOGY, UNIVERSITY OF CALIFORNIA (SANTA BARBARA AND LOS ANGELES);DEPARTMENT OF GEOLOGY AND GEOPHYSICS, PENNSYLVANIA STATE UNIVEIRSITY;

AND CALIFORNIA DIVISION OF MINES AND GEOLOGY

Conmunicated December 30, 1968

Abstract. Both procaryotic and eucaryotic nannofossils occur in chert fromthe upper Beck Spring Dolomite (Pahrump Group) in northeastern San Bernar-dino County, California. These fossils include the oldest reasonably certainrecords to date of chlorophycean and chrysophycean algae, and hence of theeucaryotic or mitosing cell. Associated with these are cyanophycean procaryotesof still more ancient affinities. Indirect radiometric evidence implies an age of1.2 to 1.4 aeons (1.2 to 1.4 X 109 years) for the enclosing rocks. Associatedstromatolites are consistent with such an age assignment.

Introductioti. In seeking to build a durable framework of knowledge aboutpre-Paleozoic life, special demands are placed on those reporting downward ex-tensions in time for the appearance of major biological innovations. They mustbe sure of their facts. After the origin of life itself and the evolution of an auto-trophic style of life, the appearance of the mitosing (eucaryotic) cell is the mostsignificant event in evolution, for all subsequent elaborations are built on it. Allbiologists and biogeologists would like to know when eucaryotes first appeared.

Thus, although the fossils here reported were first collected, identified, andrecognized as significant in 1966, we have delayed publication until we could re-solve reservations about their nature and provenance. Our reservations werefinally removed by a joint field excursion in November 1968, when we found newand much better material at the same stratigraphic level at a new locality somemiles from the discovery locality and in another mountain range. This newmaterial is localized within partially silicified stromatolites. Field and micro-scopical studies of outcrops and samples at both localities reveal no reasonablealternative to all components of the host rocks being essentially contemporaneous,and to some of the included microscopical remains being eucaryotic.

Justice cannot be done to the quality and variety of this microflora in a shortpaper. Its definitive analysis and detailed systematics will comprise a substan-tial part of Licari's doctoral thesis. Our objective here is merely to make its

623

6GEOLOGY: CLOUD ET AL.

salient features available to other workers in the rapidly evolving field of pre-Paleozoic microbiology, pending completion of comprehensive studies.

Field Relations.-The location and stratigraphic position of the discoverylocality (Cloud's locality 3 of 24/11/66) are shown in Figures 1 and 2. Thenannofossils occur in chert masses within microcrystalline gray dolomite about40 feet below the top of the Beck Spring Dolomite at this locality, about a mileeast-southeast of the Acme Talc -Mine. At the second locality (3 of 8/11/68),in the northern Kingston Range, the fossils are found in silicified parts of gen-eralized "cabbage-head" stromatolites (sedimentary structures of algal origin)at the top of the Beck Spring Dolomite. The fossiliferous beds are about 10,000feet below the lowest definitely Cambrian fossils and about 8,000 feet beneaththe lower part of the Wood Canyon Formation, which contains trace fossils in-dicative of metazoan activity.The cliff-forming Beck Spring Dolomite is the middle formation of the Pah-

rump Group of later Proterozoic age. It is underlain by the Crystal SpringFormation, which rests unconformably on intensively metamorphosed and de-formed older gneisses and schists; and it is overlain by the Kingston Peak For-mation, which contains tillite-like deposits and which is itself unconformablyoverlain by the Noonday Dolomite.Age.-The broad stratigraphic relations of the Pahrump Group' (Figs. 1 and 2)

indicate only that it is of Precambrian age. Two other approaches, however,are available in narrowing down the probable age of the Pahrump, and henceof the Beck Spring Dolomite and its contained fossils. These are (1) correlationwith rocks that elsewhere are radiometrically dated, and (2) bracketing betweenstromatolites whose ranges elsewhere appear to be stratigraphically limited.The Pahrump generally has been referred to "later Precambrian" time be-

cause of its profoundly unconformable relations with the underlying "earlierPrecambrian" crystalline rocks, giving metamorphic ages of about 1.7 aeons.2' 3Although the Crystal Spring Formation is intruded by diabase, and both it andthe Kingston Peak, as well as the Johnnie (Fig. 1), contain probable ash layersthat might give independent radiometric ages, no dates on any of this materialare yet available to us. An indirect approach to dating is available, however.The diabase bodies that intrude but apparently do not reach above the CrystalSpring Formation closely resemble, in lithology and geologic setting, an arrayof similar bodies that intrude what are probably correlative sedimentary rocksof the Apache Group in Southern Arizona and that yield essentially concordant.radiometric dates implying an age of 1.2 to 1.4 aeons.4-6

Because the Beck Spring succeeds the Crystal Spring with only inconspicuousinterruption in sedimentation, and inasmuch as clasts of the diabase are found inconglomerates of the Kingston Peak, we infer that there is no great difference inage between the Beck Spring and the Crystal Spring and that neither can bemuch older than the intrusive diabase. If this diabase is correctly judged torepresent the same magmatic event as that which intrudes the Apache Group inArizona, the age of the Beck Spring Dolomite and associated algae presumablyalso is somewhere near 1.2 to 1.4 aeons.

Provisional information on stromatolite ranges is consistent with such an age

624 PROC. N. A. S.

GEOLOGY: CLOUD ET AL.

assignment. The lower merm-ber of the Johnnie Formationat the south end of the IbexHills, west of the area shownin Figure 2, contains stromato-lites that are referable toLinella and Paniscollenia of theVendian beds of the USSR(locality 2 of 24/11/66 in Fig.1); and the very distinctiveVendian and upper Ripheanform Boxonia occurs about 400feet below the top of theJohnnie north of the areashown in Figure 2. Theseforms imply a very late Pro-terozoic or very early Paleo-zoic age for rocks that truncatethe whole of the PahrumpGroup with striking erosionaland angular uncomformity andthus suggest the Pahrump tobe much older. The CrystalSpring Formation within themapped area (at locality 1 of7/11/68, Fig. 1) contains alarge Baicalia-like stromato-lite, a form which in the USSRranges from middle into lowerupper Riphean, implying anage range of 0.9 to 1.3 aeonsaccording to consistent radio-metric dates on glauconiteand associated intrusive rocks.The possible age range impliedby the stromatolites is thusconsistent with the range of1.2 to 1.4 aeons suggested byindirect radiometric evidenceas the age of the Beck Springnannofossils.

<C)s.sLower Cambrian

N WOOD CANYON Metazoao FORMATIONU.2-j2300'

0 STIRLINGN QUARTZITE .-_ -*2 2000'

aol teC\.ooli t .. e- volcanic ash ?o JOHNNIE J3O FORMATIONo 2200' . 2l. 2of 24/11/66i .',(stromotolites)

iE NOONDAYLLI DOLOMITE vertical tubes:

1500 of unknown origin

KINGSTON PEAK ..FORMATION . p-i.2500'k

o 2500. 0 ;.......*- volcanic ashO ________..0 3 of 241/11/66o X BECK SPRING 3of 8/11/68UJI~~~~~~~~~~s~~~ (nonnofossils,

_J DOLOMITE bs stromotolites)cl a 1200'0.. X-d io bo- + volcanic ash ?

tz CS~pYRSITA ert jf --S

diobose :0

U~=-w. CRYSTAL -,\

SPRING~~~~~~~Iof 7/11/68FORMATION cs (stromatolites)

4400'

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FIG. L.-Stratigraphic sequence, Alexander Hills andvicinity, eastern California.

The Microbiota.-A variety of microstructures has been observed in thin sec-tions of the chert, of which some are clearly microorganisms, others are clearlynonvital structures, and some are problematical. Of those which are confidentlyinterpreted as Proterozoic fossils on grounds of demonstrable endemism in rela-

VOL. 62, 1969 6253

GEOLOGY: CLOUD ET AL.

tion to mineral boundaries and localization within the rock, abundance, narrowsize range, composition, and complexity of morphology resembling that of livingorganisms, six main varieties are here briefly described (types a tof).Although representatives of most of these categories are observed at both

localities mentioned above, they appear to comprise two different assemblages.The best-preserved and most numerous of these nannofossils are in cherty, early-replacement masses within dolomitic stromatolites of the upper Beck Spring inthe Kingston Range (Cloud's locality 3 of 8/11/68). This assemblage is domi-nated by filamentous and other colonial forms that appear to be related to con-struction of the "host" stromatolites. Thin sections of these cherts display alight amber-brown color due to their high content of kerogen-like material.

V; - - i{lI~r.\fkj,\;, ~. _ -.-I

,.,,,.. A.

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9-I-

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Z4~~~~~~~pa x...../

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._ SZ

0 -if --LIFEXILX 1Ei10

FIG. 2.-Geology of the Alexander Hills, south end of Nopah Range, eastern California(mapping by L. A. Wright), showing locality 3 of 24/11/66.

626 PROC. N. A. S.

GEOLOGY: CLOUD ET AL.

Laminations rich in carbonate may alternate with chert laminae in which fila-mentous and globular nannofossils are so numerous as to make some layersalmost opaque. The excellent preservation of this microbiota, and the alternat-ing laminae of chert and dolomite in some thin sections, implies a very earlydiagenetic origin for the silica. The nonstromatolitic assemblage of locality 3of 24/11/68 (Figs. 1 and 2) consists primarily of subglobular unicells that sug-gest a planktonic association.

Cyanophycean filaments-type a (Figs. 3-5): Type a includes the most abun-dant fossils in the stromatolitic chert from locality 3 of 8/11/68. They are tubu-lar, nonbranching, septate, Gunfiintia-like, presumably sedentary filaments 2-2.5 IA in diameter and up to hundreds of microns long. They form mats seen inthin section as fossiliferous laminations (Fig. 4). Septation is generally regular(Figs. 4 and 5), but larger, clear, heterocyst-like cells are spaced along some fila-ments, and some wider, more irregular filaments may represent a different cate-gory of organism (Fig. 3). The presence of enlarged cells resembling the hetero-cysts of living nostocacean algae suggests a similar function in starch storageand reproduction and favors assignment to the nostocacean cyanophytes (blue-greens) for filaments of type a.Some of these filaments appear to be replaced by hematitic pseudomorphs

after pyrite. Chains of such pseudomorphs display a sinuous pattern of globularand keg-shaped microstructures, often in parallel alignment with kerogenousfilaments. Although the hematitic chains are somewhat larger in diameter(4-8 ,u) than the associated kerogenous filaments, their geometry and associationargue for their representing altered pyritized filamentous algae, and the dif-ference in apparent size may be a result of differences in preservation. A similarinterpretation was made of pyrite chains in recent lake sediments.7

Stromatolite-associated unicells of chlorophycean affinities types b and c (Figs.6 and 9): A common variety (type b) of globular nannofossil that has been ob-served only at locality 3 of 8/11/68 includes reticulate-surfaced, alveolar cells12-25 , in diameter (Fig. 6). The best-preserved unicells occur singly or in pairs.Bodies of the same size-range, but lacking such well-preserved surface ornamen-tation, comprise many-celled aggregates in some laminations. Cells may bemutually compressed, giving rise to pseudofilamentous structures. Nearly allsuch cells possess dark spots or internal dark areas.

Unicells of type c have also been observed only at locality 3 of 8/11/68. Theyoccur as individuals or aggregates (Fig. 9), sometimes associated with cells oftype b. The type c unicells are exceptionally large for pre-Paleozoic nannofossils,ranging from 40 to 60,u in diameter. Dark spots and bands suggestive of eu-caryotic cell organelles are observed within these cells, and sections that cuttheir walls suggest a complex wall structure. Size, probable complexity of wall,and internal structures all imply a eucaryotic nature for the type c unicell. Bothcategories of stromatolite-associated unicell have their closest resemblancesto the green algae, the Chlorophyta, and general similarities to the orderChlorococcales.

Planktonic(?) unicells of chlorophycean, chrysophycean, and uncertain affinities-types d-g (Figs. 7, 8, and 10-12). A variety of minute, globular, and commonly

VOL. 62, 1969 627

GEOLOGY: CLOUD ET AL.

t. =*> > ill w|r % _Mai 3EF

i,---tt, Sll_ w is-... * ...a. i_S... w. l l_w 1t F..._..

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Figs. 3-6 and 9 from location 3 of 8/,11/68; Figs. 7, 8, and 10-12 from 3 of 24/11/66.

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628 PROC. N. A. S.

V.,OW.-T4,xv.5. 5p

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GEOLOGY: CLOUD ET AL.

FIG. 3.-Irregular filament of myxophycean affinities-type a? [slide C250 (1)].FIG. 4.-Mat of myxophycean filaments of type a preserved in silicified laminae of stroma-

tolites [slide C250 (1)].FIG. 5.-Regularly septate filament of type a passes from amber-brown chert into area of

clear silica [slide C250 (2)].FIG. 6.-Spheroids of type b with reticulate surface ornamentation [slide C250 (1)].F1G. 7.-Smooth-surfaced cell of type d with internal dark spot [slide C74 (9)].FIG. 8.-Assemblage of smooth-surfaced cells of type d with internal dark spots that

suggests pyrenoid bodies and implies chlorophycean affinities [slide C74 (9)].FIG. 9.-Aggregate of large unicells of type c with internal dark areas [slide C250 (1)].FIG. 10.-Siiceous cell of type e with prominent plug resembling chrysophycean statospore

[slide C74 (6)].FIG. I1.-Granular-surfaced cell of typef with numerous short spines [slide C74 (9)].FIG. 12.-Dark, reticulately ornamented cell of type f with long spine and surface ridges

[slide C74 (6)].

spiny-surfaced nannofossils, suggesting a planktonic association, is found in thenonstromatolitic black chert of locality 3 of 24/11/66 and sparingly in the stro-matolitic chert of locality 3 of 8/11/68.

Unicells of type d (Figs. 7 and 8) include smooth-surfaced spheroids 5-7 , indiameter which consistently include dark spots suggesting the preservation ofeucaryotic cell structures such as pyrenoid bodies (or even nuclei?). They occursingly (Fig. 7) and in small clusters (Fig. 8). Their morphology and habit wouldbe consistent with assignment to living green algae of the families Chlorosphaera-ceae or Chlorococcaceae, and they also resemble the slightly larger and thicker-walled fossil Glenobotrydium Schopf.8 In any case, assignment to the Chloro-phyta is made without reservation.The type e unicell (Fig. 10), contrary to the above-described kerogenous micro-

structures, consists of bodies composed of a mineral slightly more refractive thanthe silica matrix, possibly also silica. These 6-8 MA diameter bodies have a micro-granular surface and a stout and prominent pluglike projection. Smaller, thinnerspines are also present on some specimens. These fossils occur sparingly in boththe presumably planktonic microassemblages of locality 3 of 24/11/66 and areassociated with chertified portions of stromatolites at locality 3 of 8/11/68.They resemble in detail the siliceous statospores or cysts of certain yellow-brownalgae, the Chrysophyta.The type f unicell shows the same size range (5-8 u) as do types d and e, but

its wall seems to be kerogenous, it has a reticulate or spiny surface, and it isornamented with one to many longer spines of a more birefringent mineral thanthe chert matrix. This may be a composite type, and we have had our mis-givings about its vital origin, particularly questioning the refractive crystal-likespines. Tentatively we suggest affinities with type e and the chrysophytes, butsome euglenophytes possess similar spiny protuberances.

Conclusions.-Both sedentary blue-green algae and probably planktonic greenand yellow-brown algae occur in cherts of the upper Beck Spring Dolomite.Partially chert-replaced, biogenic sedimentary structures (stromatolites) con-tain an assemblage of microorganisms that is dominated by probably sedentaryblue-green filamentous algae and which also includes unicelled green algae. Asecond, probably planktonic, microflora is found in nonstromatolitic cherts, andsparingly in the stromatolites. It consists of solitary and aggregated unicells ofgreen and yellow-brown algal affinities.

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GEOLOGY: CLOUD ET AL.

Thus the eucaryotic cell was already in existence as early as 1.2 aeons and

possibly as early as 1.4 aeons ago, a fact which implies the availability of at leasta minimal level of free oxygen by then. This is the oldest record of eucaryotes sofar known. The beautiful and important Bitter Springs microbiota of central

Australia8 is very uncertainly dated, but is probably not as old as an aeon.9-'The eucaryotic nannofossils from the Hector Formation in Balif Park, Alberta,12may be older than an aeon, but their age has not been established, and they areprobably not as old as the Beck Spring fossils.The major preconditions for the origin of the 'Metazoa free oxygen and the

eucaryotic cell-were thus present by about 1.2 to 1.4 aeons ago. The -Metazoamight have arisen at any later time that all conditions were sufficient, includingthe level of available free oxygen.13' 14

This new datum in the microbiological record is one more evidence that well-

preserved nannofossils are indeed widespread and abundant in pre-Paleozoicrocks, and that in time we shall be able to produce a much better model of bio-logical processes and events on the primitive earth than is now available.

Our thanks toA. A. Semikhatov of the Institute of Geology, Academia Nauk, USSR,for informationon stromatolite zonation.

* The research of Cloud and Licari was supported by NASA grants N(G1-05-007-169 andNGR-05-010-035, andby NSF grant GB-7851; that of Wright by the Pennsylvanlia StateUniversity; and that of Troxel by the California Division of iIines and(eology.

1 Hewett, D. F., "Geology and mineral resources of the Ivanpah quadrangle, California andNevada," U.S. Geol. Sorv., Profess. Papers, 275, 25-28 (19.56).

2 Wasserburg,G. J.,G. W. Wetherill, and L. A. Wright, "Ages in the Precambrian terraneof Death Valley, California," J. Geol., 67(6), 702-708 (1959).

Silver, L. T., C. 1'. McKinney, and L. A. Wright, "Some Precambrian ages in the Pana-mint Range, Death Valley, California," Geol. Soc. Am., Spec. Papers, 68, 55 (1962).

4Livingstone, 1). E., and Paul E. Damon, "The ages of stratified Precambrian rock sequencesin central Arizona and northern Sonora," Can. J. Earth Sci., 5(3), pt. 2, 763-772 (1968).

5Shride, A. F., "Younger Precambrian geology in southern Arizona," U.S. Geol. Stirv.,Profess. Papers, 566, 76-77 (1967).

6 Silver, L. T., "Age determinations on Precambrian diabase differentiates in the SierraAncha, Gila County, Arizona," Bull. Geol. Soc. Am., 71(12), pt. 2, 1973-1974 (1960).

7 Cowgill, U. M., and G. E. Hutchinson, "A general account of the basin and the chemistryand mineralogy of the sediment cores," in The History of Lagina de Petenxil, a Small Lake inNorthern Guatemala (Connecticut Acad. Arts and Sci., 1966), Memoir 17, pp. 2-62.

8 Schopf, J. W., "Microflora of the Bitter Springs Formation, Late Precambrian, centralAustralia," J. Paleontol., 42(3), pt. 1, 651-688 (1968).

Dunn, P. R., K. A. Plumb, and H. G. Roberts, "A proposal for time-stratigraphic sub-division of the Australian Precambrian," J. Geol. Soc. Australia, 13(2), 593-608 (1966).

10 Compston, Wm., and P. A. Arriens, "The Precambrian geochronology of Australia,"Can. J. Earth Sci., 5(3), 561-583 (1968).

11 The occurrence of the stromatolite Jurusania (Cloud and Semikhatov, in preparation) inthe Love Creek Member of the Bitter Springs Formation would seem to bracket the age be-tween about 950 and 570 million years if the Russian stromatolite zonation is accurately datedand applies worldwide.

12 Licari, Gerald, and P. E. Cloud, Jr., "Eucaryotic nlannofossils in kerogens from the pre-Paleozoic Windermere Series of Alberta," in Abstracts, 1968 Annual Meeting of the GeologicalSociety of America, pp. 174-175.

13 Berkner, Lloyd, and L. C. Marshall, "History of major atmospheric components," thesePROCEEDINGS, 53, 1215-1225 (1965).

14 Cloud, P. E., Jr., "Pre-metazoan evolution and the origins of the Metazoa," in Evolutionand Environment, ed. E. T. Drake (New Haven: Yale Univ. Press, 1968), pp. 1-72.

630 PRO)C.. N. A.S.