Current molded, storm damaged, sinuous columnar stromatolites From Ectasian Mesoproterozoic China

Current molded, storm damaged, sinuous columnar stromatolites: Mesoproterozoic of northern China

Authors:

Tosti et al

Abstract:

A thin (~ 50 cm) horizon of sinuous stromatolites occurs within a succession of elongate upright columns in the ~ 1.4 Ga Tieling Formation, near Jixian, China. The upright columns form aligned closely spaced ridges, separated by narrow runnels with signs of current scour. The sinuous and upright stromatolites, and their intervening matrix, were originally mainly composed of carbonate mud. In end-on view, the sinuous columns incline back and forth. Each column consists of well-defined laminae that successively rotate relative to column curvature, maintaining their orientation approximately at right-angles to the column axis. In inclined parts of the columns, laminae are typically asymmetric and the steeper side faces the direction of column inclination. We interpret this column sinuosity to be a response to changes in current-direction, with accreting laminae facing into currents that supplied sediment. We find no evidence for heliotropism (mat growth towards the sun) in these examples. Adjacent columns typically show similar shapes, bending back and forth together, but their angles of curvature and inclination can change laterally from column to column, from near vertical to 45°, over distances of 30 cm. Columns can show breakage and separation of adjacent laminae. Some of this is enhanced by compaction and stress, but the occurrence of sinuous columns on their sides or upturned, in spaces between undisturbed columns, indicates that column curvature developed during growth and that toppling of columns was syndepositional. We infer that sinuosity developed in response to changes in current direction, that column inclination reflects current strength, and that breakage and toppling was produced by strong currents. Curved and sinuous columns could reflect shoaling. This would also have exposed them to storm damage and to the effects of currents that scoured sufficient matrix to locally break and topple columns. Markedly sinuous Mesoproterozoic columns also occur in Siberia and North America, suggesting that similar conditions and processes of stromatolite formation may have been widespread at this time. Formation and preservation of the sinuous stromatolites described here required a combination of conditions that included abundant fine-grained carbonate sediment, microbial mats capable of trapping it, reduced early lithification, and absence of bioturbation.

The Implications of a Stromatolite From the Olenekian (Spathian) Triassic of China

Upper Lower Triassic stromatolite from Anhui, South China: Geobiologic features and paleoenvironmental implications

Authors:

Luo et al

Abstract:

Widespread stromatolites and other microbialite deposits characterize Lower Triassic marine successions worldwide. This study documents a stromatolite deposit, 1.1 m thick, from the upper Spathian (Lower Triassic) of the Susong area, South China. The stromatolite comprises distinct laminated domes in the basal part and columns at the upper part. Dark laminae are loosely spaced and interlayered with thicker light colored laminae. Diffusive dark colored laminae are composed of peloidal micrite that grade locally into microclotted structures, and yield copies of bacteria clump-like and coccoid-like spheroid aggregates. The former are characterized by cloudy, micrite nuclei rimmed by coarse-grained, euhedral sparry calcite crystals, while the latter are comprised of solid calcite crystal nuclei coated with rather thin micrite envelopes. The cloudy, micrite nuclei resemble bacteria clump-like structures observed in present-day travertine. Both the coccoid-like spheroids and bacteria clump-like structures are surrounded by coarse-grained euhedral calcite crystals, suggesting a similar accretion mechanism. Both spherical structures therefore could be crucial in the accretion of the Susong stromatolite. The laminated/microclotted structures are interpreted as the result of variation in timing of lithification relative to the timing of the decay of microbes. Micro-analysis also unravels the common occurrence of authigenic micro-quartz crystals in association with Fe-bearing illite clay minerals in the stromatolite columns. Their coalescing nature with each other, together with the associated pyrite grains, strongly support the formation of micro-quartz crystals from microbial reduction of an Fe-bearing smectite precursor by sulfate reducing bacteria. A comparison of the Susong stromatolite with its counterparts from the upper Lower Triassic strata in Dajiang, South China reveals many similarities in stromatolite microstructures, suggesting that a harsh, euxinic–anoxic environment resulting in the bloom of sulfate reducing bacteria most likely extended into the latest Spathian in South China.

The Problems With Using Stromatolites for Detecting Paleoenvironments

Chemical and textural overprinting of ancient stromatolites: Timing, processes, and implications for their use as paleoenvironmental proxies

Authors:

Petrash et al

Abstract:

Shale-normalized Rare Earth Element (REESN) patterns and transition metal abundances in banded iron formations (BIF) and shales have long been used as paleoenvironmental proxies to investigate the evolving geochemistry of Precambrian oceans. Apparent similarities between the REESN of modern stromatolites and contemporary seawater values also mean that some ancient stromatolites could record paleo-ocean chemistry. To test this hypothesis, we present comparative mineralogical, textural, and spectral analyses of multifurcate, silicified and iron oxide/carbonate-rich, stromatolites from the ca.1.88 Ga Gunflint Formation (Ontario, Canada). Previous studies show that these organo-sedimentary structures represent the initiation of shallow marine sedimentation in the Animikie Basin on the southern tip of the Superior Province. We present evidence that these structures were originally stabilized by aragonite and Mg-bearing carbonates. Fabrics indicative of stromatolite accretion under local hypersaline conditions are also present, with La anomalies suggestive of laterally variable freshwater runoff. The admixture of partially evaporated seawater and silica-oversaturated deep seawater led to pervasive silicification of metastable carbonates and preservation of less soluble early diagenetic carbonate cements. Bulk rock transition metal contents point to lateral variability and dissimilar partitioning and fractionation during mineral formation, yet Ce anomalies amongst samples are similar. Considering the pronounced differences between the REE partitioning between Fe oxyhydroxide precipitates and carbonates, our results point to hematite and siderite as secondary minerals that postdate the stabilization of these structures by carbonates and silica. Stratabound relations of the Fe-rich stromatolites with diabase sills and dikes indicate that the pore water fluids evolved towards a localized state of hematite and siderite oversaturation towards the Mesoproterozoic. If hematite and siderite are both early diagenetic phases, then the Ce anomalies of these stromatolites may be a poor measure of the redox conditions of the shallow areas of the Animikie Basin at the time of accretion.

Evidence of Successions of Different Microbial Biota From MesoArchean South Africa

Sedimentology and facies analysis of Mesoarchaean stromatolitic carbonate rocks of the Pongola Supergroup, South Africa

Authors:

Shishi et al

Abstract:

The c. 3.0 Ga old Chobeni Formation (Nsuze Group, Pongola Supergroup) contains several carbonate successions interpreted to have been deposited in a tide-dominated, shallow-marine environment. Facies consist of mixed siliciclastic and carbonate rocks and include subtidal cross-bedded sandstone and oncolitic dolostone, intertidal wave-rippled oodolarenite, and supratidal wrinkly-laminated dolarenite–dololutite. Sedimentary facies are partially arranged in a shallowing-upward pattern reflecting cyclic variations of Mesoarchaean sea level. Microbialites occur in a variety of sedimentary sub-environments and include laminated as well as structureless, lenticular-domal types. Differences in microbialite morphology, macrofabric, and size suggest potentially distinct assemblages of microorganisms responding to different physicochemical and environmental conditions. Microbialite textures are consistent with in situ carbonate precipitation and to a lesser extent by trapping and binding of sediment. Despite their great age, the Pongola carbonates are compositionally and texturally very similar to much younger carbonate successions preserved in the geological record.

Pondering the Precambrian #1

Archean:

A study used diamonds to suggest the start of plate tectonics was approximately 3.5 billion years ago during the PaleoArchean.

Carbon deposited in the PaleoArchean Australia appears to be biological in origin.

Another study claims plate tectonics started 3 billion years ago during the MesoArchean through the examination of granites and magnesium.

The Helen Iron Formation in Canada was formed during the NeoArchean, 2.75 billion years ago, in moderately deep water when underwater volcanism ceased for a time.

There is evidence of NeoArchean plate tectonics in India

PaleoProterozoic:

Oxygen levels during the PaleoProterozoic Great Oxygenation Event may have been higher than the following Proterozoic steady state.

MesoProterozoic:

Evidence of freshwater stromatolites have been found from the Stenian of Michigan in the Copper Harbor Conglomerate.

There is paleoclimatic evidence also from the Stenian of Michigan.  The paleosols appear to indicate it was a floodplain.

NeoProterozoic:

Evidence from China gives insight into marine plate subduction during the Tonian.

Evidence from the Doushantuo Formation in China suggest the Ediacaran there had a carbon anomaly and the phosphated embryos found predate the Gaskiers Glaciation.

*GIANT* (5.5m high and 7m diameter) Stromatolites From Eocene Paleogene Wyoming

Giant stromatolites of the Eocene Green River Formation (Colorado, USA)

Authors:

Awramik et al

Abstract:

The Eocene Green River Formation in the Sand Wash Basin, Colorado (United States), contains the largest known lacustrine columnar stromatolites. Spectacular columns, as much as 5.5 m high with diameters of 7 m, occur over a broad area. The stromatolites are composed of laterally continuous centimeter-thick layers that can be traced from the base to the top of the column (synoptic relief), thus these stromatolites stood as much as 5.5 m above the lake floor. The layers consist of one to several different kinds of microbialites, which makes these large columns even more unusual. The giant columns were the result of a combination of factors including the lake transgressing a flooded woodland, in situ tree stumps providing elevated substrates above the lake floor, an abundant supply of calcium-rich spring and surface water that mixed with saline-alkaline lake water, and the subsidence rate of the nearshore lake environment not exceeding the rate at which the stromatolites grew.

Exordinary Claim: Curiosity Mars Rover has Seen Structures Like Microbial Fossils on Earth

Ancient Sedimentary Structures in the less than 3.7 Ga Gillespie Lake Member, Mars, That Resemble Macroscopic Morphology, Spatial Associations, and Temporal Succession in Terrestrial Microbialites

Author:

Noffke

Abstract:

Sandstone beds of the less than 3.7 Ga Gillespie Lake Member on Mars have been interpreted as evidence of an ancient playa lake environment. On Earth, such environments have been sites of colonization by microbial mats from the early Archean to the present time. Terrestrial microbial mats in playa lake environments form microbialites known as microbially induced sedimentary structures (MISS). On Mars, three lithofacies of the Gillespie Lake Member sandstone display centimeter- to meter-scale structures similar in macroscopic morphology to terrestrial MISS that include ‘‘erosional remnants and pockets,’’ ‘‘mat chips,’’ ‘‘roll-ups,’’ ‘‘desiccation cracks,’’ and ‘‘gas domes.’’ The microbially induced sedimentary-like structures identified in Curiosity rover mission images do not have a random distribution. Rather, they were found to be arranged in spatial associations and temporal successions that indicate they changed over time. On Earth, if such MISS occurred with this type of spatial association and temporal succession, they would be interpreted as having recorded the growth of a microbially dominated ecosystem that thrived in pools that later dried completely: erosional pockets, mat chips, and roll-ups resulted from water eroding
an ancient microbial mat–covered sedimentary surface; during the course of subsequent water recess, channels would have cut deep into the microbial mats, leaving erosional remnants behind; desiccation cracks and gas domes would have occurred during a final period of subaerial exposure of the microbial mats. In this paper, the similarities of the macroscopic morphologies, spatial associations, and temporal succession of sedimentary structures on Mars to MISS preserved on Earth has led to the following hypothesis: The sedimentary structures in the less than 3.7 Ga Gillespie Lake Member on Mars are ancient MISS produced by interactions between microbial mats and their environment. Proposed here is a strategy for detecting, identifying, confirming, and differentiating possible MISS during current and future Mars missions.

Stromatolites From Anisian Triassic Southwest China

Early Middle Triassic stromatolites from the Luoping area, Yunnan Province, Southwest China: Geobiologic features and environmental implications

Authors:

Luo et al

Abstract:

An early Middle Triassic stromatolite deposit is documented from the Guanling Formation of the Luoping area, Yunnan, SW China. The Luoping stromatolite shows five types of constructional microbial forms in various magnifications: 1) typical stratified columnar structures, up to 20 cm high, with crinkled laminae. Dark coloured laminae, 1 mm thick, are composed of upright filamentous tubes, averagely 29.4 μm in diameter, showing a vertical growth fabric. 2) Laminoid fenestrae, 0.5–1 mm wide, and 3) prostrate filaments, which are reflected by strong fluorescence in sharp contrast to dolomite cement in fluorescent images. 4) Rod-like aggregates, 4.6–18 μm in diameter, composed of minute dolomite rhombs, are very common in stromatolitic laminae; they resemble present-day cyanobacterial trichome, and thus may represent putative fossilized cyanobacteria. 5) Moreover, small pits, coccoid-like spheroids, calcified biofilms, and fibrous structures are also common in stromatolitic laminae. The last two may represent calcified extracellular polymeric substances (EPS) that contributed to the development and lithification of stromatolites. Authigenic quartz grains are common and may also have involved biological processes in stromatolite formation. Of these microbial functional-groups driving accretion and lithification processes of stromatolite documented in literature, both lithified cyanobacteria/oxygenic phototrophs and possible sulfate-reducing bacteria (SRB), which induced microbial formation of dolomite and contributed to the accretion of the Luoping stromatolite, are suggestive of biogenic origin. The Luoping stromatolite differs from the Permian–Triassic boundary microbialites (PTBMs) in having abundant filamentous structures and growing in an oxic marine environment. Both sedimentary facies analysis and abundant fossilized cyanobacteria may indicate proliferation of oxygenic phototrophs in a normal, oxic habitat during the middle Anisian (early Middle Triassic), a period when hospitable environments, coupled with biotic diversification, prevailed in South China and set an agenda for the full recovery of marine ecosystems in middle–late Anisian. However, the post-extinction stromatolites and other anachronistic facies are not necessarily indicative of anoxic or oxic conditions, and their environmental settings are much more complex than previously thought.

NeoArchean Tumbiana Formation Conical Stromatolites Were From Phototrophic Microorganisms?

Sedimentology, stratigraphy and geochemistry of a stromatolite biofacies in the 2.72 Ga Tumbiana Formation, Fortescue Group, Western Australia

Authors:

1. J.M. Coffey (a)
2. D.T. Flannery (a)
3. M.R. Walter (a)
4. S.C. George (a, b)

Affiliations:

a. Australian Centre for Astrobiology, School of Biotechnology and Biomolecular Sciences, University of New South Wales, New South Wales 2052, Australia

b. Department of Earth and Planetary Sciences, Macquarie University, New South Wales, 2109, Australia

Abstract:

The 2.72 Ga Tumbiana Formation is a succession of clastic and carbonate rocks outcropping along the southern margin of the Pilbara Craton in Western Australia. It hosts abundant, diverse and exceptionally well-preserved stromatolites and has provided the setting for numerous investigations focussing on the Archean biosphere. Despite its palaeobiological significance, the overall depositional setting of the Tumbiana Formation remains unclear. Here we present the results of stratigraphic, sedimentological and geochemical investigation of the Tumbiana Formation in the well-known Redmont/Knossos area and at several localities in the northwestern Pilbara sub-basin. We suggest these data are best explained by deposition in fluvial and lacustrine environments of an inward-draining continental basin. δ13Corg values vary from -49.9‰ to -15.0‰. Conical stromatolite morphologies, commonly attributed to cyanobacteria, are anomalously little depleted in 13Corg, implying a higher relative contribution of organic matter from phototrophic versus methane cycling metabolisms.