Early proterozoic pillow lavas of Suisari as habitats of the earliest microorganisms

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<ul><li><p>ISSN 00310301, Paleontological Journal, 2013, Vol. 47, No. 10, pp. 11101115. Pleiades Publishing, Ltd., 2013.</p><p>1110</p><p>INTRODUCTION</p><p>The development of life in volcanogenic rocks ofthe remote past and colonization by microorganisms(both ancient and modern) of the boundary (surface)between the volcanogenic rock and water (deposits)are presently widely debated (Rasmussen, 2000; Fisket al., 2003, 2006; Furnes et al., 2004, 2007;McLoughlin, 2007; Astafieva et al., 2008, 2009a,2009b; Rozanov and Astafieva, 2009). The modernmicrobial life has been recorded in both surface rocksand deep underground. As commonly believed, mostof the biomass of microorganisms of the Earth occur inunderground habitats. Microorganisms dwell in dampcracks of volcanogenic rocks and are recorded byimprints in the rock or by chemical remains of the vitalactivity. On the other hand, in nearsurface conditions, modern microbial life is frequently closely connected with the volcanogenic rockwater interface(Fisk et al., 2006).</p><p>Volcanogenic and volcanogenicsedimentaryrocks (where the surfaces of the volcanogenic rockwater interface boundaries occur) of the Archeangreenstone belts (GSB) of western Greenland, SouthAfrica, and Australia are the most ancient terrestrialrocks, which enclose microfossils.</p><p>The most ancient extinct microorganisms connected with this interface were described from MesoArchean pillow lavas of the Barberton GreenstoneBelt in South Africa. It was proposed that microbesoccupied these underwater effusive rocks just aftereruption about 3.5 Ga (Furnes et al., 2004). Schopf(1993) was the first to discover fossil filamentousmicroorganisms resembling cyanobacteria in the EarlyArchean (3.465 Ga) rocks of western Australia. The</p><p>criticism of these early finds (Brasier et al., 2002)seems to have little force. Another record of Archean(3.235 Ga) microfossils in volcanogenic rocks comesfrom the sulfide volcanogenic strata in the PilbaraCraton in Australia. In this case, bacteria wererecorded in a system of underwater thermal springs(Rasmussen, 2000).</p><p>It is known that pillow lavas are formed as a resultof underwater flow of basalt lavas. Sometimes, pillowsreach several meters in thickness. In cross sections ofpillows, the external rapidly solidifying glassy crustand more devitrified internal core, often containingradial aggregates, are clearly visible. Gaps betweenlava pillows are filled with either sedimentary matteror products of lava disruption, small glassy debris. Fossil bacterial assemblages from different parts of pillowlavas have not been compared; therefore, it is urgent tostudy the distribution of microorganisms in solidifiedpillow lavas. The study of microfossils from the glassymatrix of Early Paleoproterozoic pillow lavas and theircomparison with extant forms suggest that recent andancient basaltic glasses of pillow lavas contain ratherdiverse microbial assemblages. It has been shown thatboth assemblages are dominated by various filamentous taxa and contain forms tentatively referred to prasinophytes, i.e., eukaryotes. At the same time, cocciand oval forms were probably subordinate (Astafieva etal., 2009). It was also corroborated that microorganisms colonized the basalt glass of Early Precambrianunderwater eruptions, as do extant microorganisms,colonizing modern volcanic glass. The present study isdevoted to prokaryotic assemblages from the interpillow debris, as well as marginal and internal parts of pil</p><p>Early Proterozoic Pillow Lavas of Suisari As Habitats of the Earliest Microorganisms</p><p>M. M. Astafievaa, A. A. Chistyakovb, M. M. Boginab, and E. V. SharkovbaBorissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Moscow, 117997 Russia</p><p>email: astafieva@paleo.rubInstitute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM), Russian Academy of Sciences, </p><p>Staromonetnyi per. 35, Moscow, 109017 Russiaemail: bogina@igem.ru</p><p>Received June 19, 2012</p><p>AbstractAssemblages of fossilized microorganisms from the Paleoproterozoic Suisarian Formation(Ludicovian stratotype of the Karelian Complex) of central Karelia are recognized and investigated. Fossilassemblages of microorganisms confined to different zones of pillow lavas are compared.</p><p>Keywords: microorganisms, bacteria, cyanobacteria, eukaryotes, Proterozoic, pillow lavas</p><p>DOI: 10.1134/S0031030113100055</p></li><li><p>PALEONTOLOGICAL JOURNAL Vol. 47 No. 10 2013</p><p>EARLY PROTEROZOIC PILLOW LAVAS OF SUISARI 1111</p><p>lows as exemplified by the Paleoproterozoic basalticpillow lavas from central Karelia.</p><p>MATERIAL</p><p>The material includes assemblages of fossilizedmicroorganisms from the Paleoproterozoic SuisarianFormation (Ludicovian stratotype of the KarelianComplex (Resolution of the III AllRussia , 2001)dated about 2.0 Ga) of the Onega Basin in centralKarelia. The Suisarian Formation is composed ofpicrite and picrobasalt, basalt, trachybasalt and theirtuffs, and terrigenous deposits. Pillow lavas (marginaland central parts and interpillow matter) from twolocalities were examined.</p><p>(1) A locality on the Keltnavolok Cape (Fig. 1),the northernmost cape of Suisari Island, is situated in</p><p>the southeastern Kondopoga Gulf of Lake Onega. Pillow lavas of plagioclase porphyry basalt, with a moreor less pronounced variolitic structure outcrop there.The pillows consist of the aphanitic chill zone, marginal and central (core) zones. The last is composed ofthe mostly devitrified matter and frequently containsgas cavities, which are sometimes filled with chalcedony and quartz matter.</p><p>(2) A locality in the upper part of the Suisarian Formation section of the Yalguba Range is situated on thebank of Lake Onega, opposite the village of Yalguba,approximately 20 km northeast of the city of Petrozavodsk (Fig. 1). The section is dominated by plagioclasepyroxene porphyry basalts with pillow units,which form 520thickm flows. These flows alternate with massive lava flows, ranging from 35 to 1820 m in thickness.</p><p>Barents Sea</p><p>Kola Peninsula</p><p>White Sea</p><p>Lake Onega</p><p>Ladoga</p><p>Suisari Island</p><p>Yalguba</p><p>La</p><p>ke</p><p> O</p><p>ne</p><p>ga</p><p>P e t r o z a v o d s k Ba y</p><p>Petrozavodsk</p><p>1 2 3 4</p><p>5 6 7</p><p>40 70</p><p>60 30</p><p>40</p><p>70</p><p>60</p><p>30</p><p>Fig. 1. Scheme of geological structure of the northwestern Onega Region, with the object investigated (encastre). Paleoproterozoic: (1) Suisarian Formation, (2) Shoksha Formation, (3) Padosska Formation, (4) Zaonega Formation, (5) gabbrodolerites ofthe Padosska Formation; (6) Quaternary beds; (7) sampling localities.</p></li><li><p>1112</p><p>PALEONTOLOGICAL JOURNAL Vol. 47 No. 10 2013</p><p>ASTAFIEVA et al.</p><p>Bacterial paleontological studies were performedusing a CamScan4 scanning electron microscope,with a Link860 microanalyzer. Only fresh chips ofrocks were examined.</p><p>RESULTS</p><p>Bacterial paleontological studies have shown thatthe marginal regions of pillows and interpillow matterare dominated by filamentous fossils. Biofilms alsoplay an important role among fossilized remains understudy. Note that descriptions only concern fossilizedbacteria (cyanobacteria) or, more precisely, pseudomorphs of bacteria and cyanobacteria.</p><p>Marginal Regions of Pillows with Interpillow Matter</p><p>These zones have yielded diverse microfossils,including:</p><p>Filamentous forms. They are sometimes very abundant, forming an impression that they compose particular elements of the rock. This suggests that bacteriacolonized the surface of cooling lava simultaneouslywith sedimentation. Fossil filamentous forms sometimes cooccur with coccoid forms (Pl. 1, fig. 1). Thefilaments are long, up to 100 m long or even longerand about 2 m thick. The cocci are about 34 m indiameter.</p><p>The rock contains complete cavities filled withinterlacing fossilized bacterial filaments. Bacteriaapparently inhabited the surface of pillows during theformation of the interpillow matter.</p><p>There are also pseudomorphs of solitary filaments(Pl. 1, fig. 2), which are usually at most 3 m thick andmore than 20 m long. Some pseudomorphs arelarger, up to 10 m thick, and some are short tubular(Pl. 1, fig. 3). Moreover, it seems that, on the left of atubule (4b, arrow), there is an imprint of the sametubular form (4b, double arrow) and that the entirerock fragment is composed of small (up to 1 m)cocci.</p><p>The sample contains many holes, which are sometimes partially filled with rock and probably representsections of filamentous forms (Pl. 1, fig. 4). Some sections of filaments (about 10 m in diameter) are halffilled by enclosing rock, with a thick (about 1.5 m)heterogeneous cover (Pl. 1, fig. 4). Filaments ofsmaller diameter (about 5 m) are also present; theircovers are rather dense, about 1 m thick (Pl. 1, fig. 5).Many filaments are apparently completely embeddedin the rock (Pl. 1, figs. 4, 5), thus, suggesting theirundoubted in situ formation. In places, the matter isapparently composed of abundant small (up to 1 m)cocci (Pl. 1, fig. 4).</p><p>Judging from the size and morphology, all theforms in question are bacteria and (or) cyanobacteria.</p><p>Cocci are less frequent than filamentous specimens. They are mostly singular, have a rough surface,usually about 36 m in diameter. Colonies of cocci</p><p>are rare. An accumulation of cocci about 3 m indiameter is only recorded in glycocalyx, composing arock fragment (Pl. 1, fig. 6).</p><p>Biofilms and biofilm fragments are common (Pl. 2,fig. 1).</p><p>There are also larger (about 10 m in diameter)spherical forms (Pl. 2, fig. 2), united in accumulations.Perhaps, these are planktonic forms deposited on thebottom. They are similar in morphology to prasinophytes, although available data are insufficient formore precise identification. Since spherical formsusually compose rock units, they were apparently buried simultaneously with sedimentation.</p><p>Marginal Zone of Pillows</p><p>Microfossils coming from the marginal zone of pillows are also rather diverse, including:</p><p>Isolated filamentous forms (Pl. 2, fig. 3) more than30 m long and about 2 m in diameter are present.Interlacing of filaments has not been recorded.</p><p>The holes produced by filaments and filled withenclosing matter are present (Pl. 2, fig. 4).</p><p>The cocci are extremely scarce (Pl. 2, fig. 5); theyare usually less than 3 m in diameter. Only individualcocci are present, although they do not form colonies.</p><p>Biofilms are common (Pl. 2, fig. 6); some presumable biofilm fragments are treated as flattened coversof cyanobacteria.</p><p>Central Part (Core) of Pillows</p><p>Basalts of pillow lavas enclose rare microfossils, inparticular, individual pseudomorphs of filaments,tubes, and cocci. However, these microfossils were notnecessarily buried in their lifetime, because all formslie on the rock surface, not embedded into the rock.</p><p>DISCUSSION AND CONCLUSIONS</p><p>Bacterial paleontological studies of various pillowlavas, including rocks from the interpillow space, marginal and central zones, have shown significant differences in the distribution of microfossils. The mainpoint is that microfossils from the interpillow spaceand marginal regions of pillows are much more abundant and diverse than those from the central parts(Table 1).</p><p>The chemical composition of fossilized organismscorresponds in all cases (interpillow matter, marginaland central parts of pillows) to the composition ofenclosing matter. This agrees with the in situ burial ofmicroorganisms and confirms the fact that we dealexclusively with pseudomorphs and almost completelyexclude the possibility of preservation of organic matter.</p><p>Pillow lavas of the Suisarian Formation were probably formed in connection with repeated underwatereruptions; as a result, the earlier formed pillow lavaswere covered by products of later eruptions. The inter</p></li><li><p>PALEONTOLOGICAL JOURNAL Vol. 47 No. 10 2013</p><p>EARLY PROTEROZOIC PILLOW LAVAS OF SUISARI 1113</p><p>Plate 1</p><p>10 m1 2 3 m</p><p>3 m43 10 m</p><p>3 m65 3 m</p><p>E x p l a n a t i o n o f P l a t e 1</p><p>Microfossils from the marginal zones of pillows of pillow lavas with interpillow matter; central Karelia, Onega Basin, SuisariIsland; Paleoproterozoic, Suisarian Formation.Fig. 1. Interlacing filamentous forms against a background of cocci.Figs. 2 and 3. Fragments of filamentous forms: (2) thread fragment; (3) pseudomorph of filamentous (tubular) form and imprintof short and thick filamentous (tubular) forms.Figs. 4 and 5. Holes in the rock, traces of filamentous forms.Fig. 6. Coccus colony.</p></li><li><p>1114</p><p>PALEONTOLOGICAL JOURNAL Vol. 47 No. 10 2013</p><p>ASTAFIEVA et al.</p><p>Plate 2</p><p>10 m1 10 m2</p><p>10 m3</p><p>10 m4</p><p>3 m5 3 m6</p><p>E x p l a n a t i o n o f P l a t e 2</p><p>Microfossils from the marginal regions of pillows of pillow lavas with interpillow matter; central Karelia, Onega Basin, SuisariIsland; Paleoproterozoic, Suisarian Formation.Fig. 1. Biofilm fragment.Fig. 2. Spherical forms.Microfossils from the marginal zone of pillows of pillow lavas; central Karelia, Onega Trough, Suisari Island; Lower Proterozoic,Suisarian Formation.Fig. 3. Filamentous form.Fig. 4. Holes produced by filamentous forms filled with rock.Fig. 5. Individual coccoidal structure.Fig. 6. Biofilm fragment.</p></li><li><p>PALEONTOLOGICAL JOURNAL Vol. 47 No. 10 2013</p><p>EARLY PROTEROZOIC PILLOW LAVAS OF SUISARI 1115</p><p>pillow matter was also formed in the Suisarian timeduring interruptions between eruptions. The distribution of microfossils in pillow lavas (Table 1) shows thatthe most favorable conditions for the development andflourishing of life were in the deposits on the pillowlava surface, which gave rise to the interpillow matter.The marginal region of pillow lavas bordered bydeposits was also rather favorable for the developmentof microorganisms.</p><p>Thus, the present study corroborates the assumption that almost all oldest volcanogenic rocks arepromising for bacterial paleontological investigation.</p><p>ACKNOWLEDGMENTS</p><p>This study was supported by the Program of thePresidium of the Russian Academy of Sciences Problems of the Origin of Life and Formation of the Biosphere (Subprogram 2), the Russian Foundation forBasic Research, project nos. 110400129, 110500695, and 120400102, and the Russian State Program for Support of Leading Scientific Schools,project no. NSh65493.2010.4.</p><p>We are sincerely grateful to all colleagues participating in discussions and editing the manuscript andto A.V. Kravtsev and L.T. Protasevich for help inexamination using a CamScan4 SEM.</p><p>REFERENCES</p><p>Astafieva, M.M., Rozanov, A.Yu., Cornell, D.H., andHoover, R.B., Development of Living Organisms on theLavaWater Interface of Palaeoproterozoic Ongeluk Lavasof South Africa, Proc. SPIE, 2008, vol. 7097, pp. 709703170970313.Astafieva, M.M., Rozanov, A.Yu., Sadovnikov, G.N., andSapova, E.V., Fossil Bacteria from the Permotriassic Trappean Strata of Siberia, Paleontol. J. (Moscow), 2009, vol. 43,no. 8, pp. 4654.Astafieva, M.M., Rozanov, A.Yu., Sharkov, E.V., Chistyakov, A.V., Bogina, M.M., and Hoover, R.B., VolcanicGlasses As Habitat for Microfossils: Evidence from theEarly Paleoproterozoic Pillow Lavas of Karelia and TheirModern Analogues in the MidAtlantic Ridge, Proc. SPIE,2009, vol. 7441, pp. 744104174410412.Brasier, M.D., Green, O.K., Jephcoat, A.P., et al., Questioning the Evidence for Earths Oldest Fossils, Nature,2002, vol. 416, pp. 7681....</p></li></ul>