Stromatolites Research Articles

Porosity distribution in cyclic dolomites of the Lower Qiulitag Group (Upper Cambrian) in northwestern Tarim Basin, China

ABSTRACT Increasing interests in hydrocarbon resources at depths have drawn greater attentions to the deeply-buried carbonate reservoirs in the Tarim Basin in China. In this study, the cyclic dolomite rocks of Upper Cambrian Lower Qiulitag Group from four outcrop sections in northwestern Tarim Basin were selected to investigate and evaluate the petrophysical properties in relation to depositional facies and cyclicity. The Lower Qiulitag Group includes ten lithofacies, which were deposited in intermediate to shallow subtidal, restricted shallow subtidal, intertidal, and supratidal environments on a carbonate ramp system. These lithofacies are vertically stacked into repeated shallowing-upward, meter-scale cycles which are further grouped into six third-order depositional sequences (Sq1 to Sq6). There are variable types of pore spaces in the Lower Qiulitag Group dolomite rocks, including interparticle, intraparticle, and fenestral pores of primary origin, inter crystal, and vuggy pores of late diagenetic modification. The porosity in the dolomites is generally facies-selective as that the microbially-originated thrombolites and stromatolites generally yield a relatively high porosity. In contrast, the high-energy ooidal grainstones generally have very low porosity. In this case, the microbialite-based peritidal cycles and peritidal cycle-dominated highstand (or regressive) successions have relatively high volumes of pore spaces, although highly fluctuating (or vertical inhomogeneous). Accordingly, the grainstone-based subtidal cycles and subtidal cycle-dominated transgressive successions generally yield extremely low porosity. This scenario indicates that porosity development and preservation in the thick dolomite successions are primarily controlled by depositional facies which were influenced by sea-level fluctuations of different orders and later diagenetic overprinting.

LOWER TRIASSIC (INDUAN TO OLENEKIAN) CONODONTS, FORAMINIFERA AND BIVALVES FROM THE AL MAMALIH AREA, DEAD SEA, JORDAN: CONSTRAINTS ON THE P-T BOUNDARY

Upper Permian to Lower Triassic successions exposed in the Al Mamalih area, east of the Dead Sea, Jordan record the transition between the alluvial Umm Irna Formation (Upper Permian) and the overlying shallow marine Ma’in Formation (Lower Triassic). The Permian-Triassic boundary is constrained either within a hiatus represented by a sequence boundary between these formations or within ca 15 m of shallow marine beds overlying the boundary. Above the sequence boundary reddened, shallow-marine beds (Himara Member) mark the initial Triassic (presumed early Induan) marine transgression (Himara Member). Absence of both body fossils and vertical infaunal burrows indicates low-diversity, ecosystems following the Permian-Triassic extinction event. A gradational upward increase in grey, green and yellow siltstones beds (Nimra Member), accompanied by a concomitant increase in bioturbation (surface traces and infaunal vertical burrows), bivalves and brachiopods, stromatolites, conchostracans and lingulids in the lower part of the Nimra Member indicates colonisation of the substrate under shallow marine conditions during the recovery phase. Shallow-water carbonates in the Nimra Member yielded an abundant, low diversity assemblage of conodonts (e.g. Hd. aequabilis and H. agordina) and a foraminifera assemblage (Postcladella gr. kalhori-Earlandia spp.-Ammodiscus jordanensis n. sp.) that are interpreted as euryhaline recovery taxa that characterise the the mid-late Induan. Abundant new material has allowed revision of the conodont apparatus and the foraminifera include a new species Ammodiscus jordanensis n. sp. of Induan age. The discovery of the bivalves Claraia bittneri (C. aurita group) and Eumorphotis multiformis is worthy to note. Upper Permian alluvial lithofacies (Jordan) pass basinwards, about 50 km to the northwest, to coeval shallow marine siliciclastic and carbonates in the Negev and Mediterranean coast of Israel.

QUATERNARY BUILD-UPS AND RHODALGAL CARBONATES ALONG THE ADRIATIC AND IONIAN COASTS OF THE ITALIAN PENINSULA: A REVIEW

In the Mediterranean, build-ups (created by coralline algae, Cladocora caespitosa, deep-water corals, vermetids, polychaetes and bacteria) and rhodolith beds are important hot-spots of biodiversity. Being severely threatened by anthropogenic impact and climate change, they have been included in international directives on environmental protection. This work wants to support the ongoing research on modern bioconstructions by providing further data on the long-term effects of environmental factors on these habitats. Our results are based on the analysis of the existing literature on the outcropping Quaternary successions of the Adriatic and Ionian coasts of peninsular Italy. The existing reports of build-ups and rhodalgal carbonates have been summarized in an homogeneous data-set and then studied to highlight distribution patterns in space and time. The analyses consistently outlined the importance of sedimentation rate in controlling the general distribution of build-ups and rhodalgal carbonates. The majority of the reports is concentrated south of the Gargano, where the sediment-load of the rivers is small. The majority of the reports is related to coralline algae, suggesting that they were the main carbonate producers during the period. C. caespitosa general distribution is mainly controlled by temperature, with most of the occurrences dating back to the warm periods of the late Ionian and of the Tarantian. Large build-ups of Cladocora are restricted to embayments and gulfs well-protected against storm waves. The distribution of the outcrops of deep-water corals is biased by the geological setting. A remarkable uplift is necessary to bring these corals from their original deep-water setting to elevated areas onshore. Consequently, most of the outcrops are in Southern Calabria which is characterized by a strong Quaternary uplift. Chemosynthetic build-ups, intertidal bioconstructions (made by vermetids, polychaetes or coralline algae), as well as stromatolites, are rare in the study area.

The stratigraphic architecture and depositional environments of non-marine carbonates from barremian-aptian pre-salt strata of the Brazilian continental margin

The stratigraphic architecture and depositional environments of non-marine carbonates from barremian-aptian pre-salt strata of the Brazilian continental margin

Fiction: Transgressive treats

Paul L. McEuen relishes Margaret Atwood's acerbic tales of sex, hallucinations and death by stromatolite.

Modern microbial mats in siliciclastic tidal flats: Evolution, structure and the role of hydrodynamics

Fil: Cuadrado, Diana Graciela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Bahia Blanca. Instituto Argentino de Oceanografia (i); Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Bahia Blanca; Argentina. Universidad Nacional del Sur. Departamento de Geologia; Argentina

Stromatolites and MISS—Differences between relatives

Stromatolites and MISS—Differences between relatives

A Lagoa do Salgado e a Ação Antrópica em sua Faixa Marginal de Proteção, Região Norte do Estado do Rio de Janeiro

This study is about Salgado Lagoon, the anthropic action in its Protected Coastal Zone over the years and the possible impacts arising from urbanization occurred in the Acu Superport and in future enterprises in its region, by making a comparative analysis with the case of the Vigario Lagoon in the city of Campos dos Goytacazes, which suffers problems caused by an uncontrolled growth and lack of planning. The occurrence of recent stromatolites, only found in South America, included the Salgado Lagoon as a geo-paleontological site in UNESCO World Heritage list, which makes the problem even more relevant. Consequently, urgent and drastic measures must be taken to protect this geological-paleontological site.

Aspectos deformacionais em estromatólitos do Grupo Itaiacoca, a sul de Itapeva (SP)

Deformation of stromatolites were studied in metalimestones of the Itaiacoca Group (Ribeira Belt), at three outcrops located on the south of Itapeva, Sao Paulo, Brazil, with qualitative and quantitative methods. Among the stromatolites identified, we used the Conophyton on the study of the deformation, since the initial parameters are known. Different shape patterns of Conophyton found in several localities are related with the depositional environment and differences of preservation, mainly caused by deformation. The thickest lenses and beds, with larger concentration of stromatolites, are better preserved. In the Lavrinhas quarry, the stromatolites have well-defined margins and well-preserved lamination however the contrast is extinguishes on most samples due to the dolomitization/ recristalization of the metadolostones. Although in the metalimestones of the Indumine/Chiquinho of Barros quarries, the preservation of the stromatolitic lamination is commonly well-preserved, besides the columns are deformed, showing that the columns resisted to the deformation in a more rigid way than the intercolumnar sediment, with relative movements between them. They develop an intercolumnar foliation. The medium value of R s = 1,34 in the metadolostones of Lavrinhas is similar that the values of R s found in rocks of the Lajeado Subgroup (between 1,31 and 1,91), towards southeast of the analyzed localities. In Indumine the value of R s is higher (1,91) than those found in metalimestones of the Lajeado Subgroup. Therefore, the value of R s obtained for the metadolostones can be considered as a close value to the metalimestone´s medium value of the Grupo Itaiacoca, and the value of R s of Indumine is a restricted to this locality. The differences according to deformation patterns of these two lithologies are related to the distinct tectonic behavior of the more pure and competent metadolostones than the more argillaceous metalimestones, which has a more plastic behavior.

SEDIMENTAL RECORDS AND CHARACTERISTICS OF PALAEOCLIMATE AND PALAEOENVIRONMENT IN THE YANSHAN AREA，NORTH CHINA IN THE MESOPROT EROZOIC AND THE NEOPROTEROZOIC

The Proterozoic is one of critical periods Environment of the Earths surface tended to stabilization by degrees in the period Various forms of living beings in the Earth began to occur and develop A lot of studies indicated that the Rodinia supercontinent had been formed in the whole Earth at 1 0～0 8 Ga BP Then North China located in middle or low latitude region connected with Laurentia Platform and Siberia Platform The Mesoproterozoic and the Neoproterozoic in Yanshan area were deposited during the Yanshan-Liaohe Tectonic Cycle (1 8～0 85 Ga BP), and the aulacogen underwent an evolution from initiation through development to consumption in Changchen period, Jixian period and Qinbeikou period respectively The first cover upper the platform crystalline basement was formed mainly by the thick carbonate formation A series of palaeoenvironment variance took place on the Earth in the Proterozoic, such as O 2 level increased and CO 2 level reduced of the atmosphere ocean system, and it began to turn into oxidation from reduction 1 85 Ga BP ago Wide ranging red earth pile occurred with the ceasing of the banded silica-iron formations in the Earths history A large number of steranes, hopanes and isoprenoid were identified from the Precambrian samples Those show that eucaryotes, eubacteria and photoautrophs on the Earth might have appeared in the Palaeoproterozoic time A lot of organisms fossils of early stage of the Earth were found from the Mesoproterozoic Changchen system and Jixian system in Yanshan area They include eucaryotic algae, multicellular algae, coccolith, algal stromatolite, metazoan trace fossil and so on Especially the large-scale unicellular algae and macroscopic multicellular algae fossils found from Changzhougou Formation, Chuanlinggou Formation and Tuanshanzi Formation (1 8～1 6 Ga BP) of Changchen system Those discoveries are of important significance to explore the origin and evolution of different kinds of living things and recover palaeoclimate and palaeoenvironment

Algal biomodels as analogs of phosphorites, oncolites and stromatolites

Algal biomodels as analogs of phosphorites, oncolites and stromatolites

Crucial crises in biology: life in the deep biosphere.

The origin and evolution of life on Earth are the result of a series of crises that have taken place on the planet over about 4500 millions of years since it originated. Biopoiesis (origin of life), ecopoiesis (origin of ecosystems) and the first ecosystems (stromatolites and microbial mats), as well as eukaryopoiesis (origin of nucleated cells) are revised. The paper then focuses on the study of the deep biosphere, describing ecosystems never found before, which are independent of solar radiation and have changed previous assumptions about the requirements of life; even the concept of biosphere, as Vernadsky defined it, has increased its scope. Since the discovery, in 1987, of bacteria growing in the crevices of rocks at 500 m deep, in boreholes drilled near the Savanna River, Aiken, South Carolina, other bacteria have been found in the deep subsurface reaching depths of about 3 km (e.g., in the Columbia River Basalt Group, near Richland, Washington state), in an anaerobic, hot, high-pressure environment. Some kinds of microorganisms can thrive at such depths, living in many cases a geochemical existence, by using very specialized metabolisms, which depend on the local environments. The existence of organisms independent from photosynthetic production is the most outstanding, novel feature of the deep biosphere. Living beings might not need other energy and chemical sources than those which occur in the development of all planetary bodies. Life, therefore, could even be an ineluctable outcome of planetary evolution and, as a corollary, a natural continuation of the usual development of physical phenomena in the universe.

Stromatolite-thrombolite associations in a modern environment, Lee Stocking Island, Bahamas

Columnar buildups found in a tidal channel off Lee Stocking Island, Exuma Cays, Bahamas, have been interpreted as modern giant stromatolites growing in a subtidal normal marine environment. However, these organically-formed columns reveal three discernible internal structures: (1) prokaryotic stromatolites comprised of alternating layers of coarse-grained ooids and peloids, and fine micrite that formed exclusively by microbial activity; (2) eukaryotic stromatolites comprised of microbially-induced micritic layers alternating with detrital layers accumulated, bound, and cemented by eukaryotic algae; and (3) thrombolites displaying irregular, clotted fabrics and formed by microbes, algae, and metazoans. Phanerozoic thrombolites, in contrast, have been interpreted as unlaminated stromatolites constructed by cyanobacteria. Eukaryotic organisms overgrow all of the columns at present. Thus, the contemporaneous formation of prokaryotic stromatolites, eukaryotic stromatolites, and thrombolites under identical conditions within the present environment appears unlikely. We suggest that the prokaryotic stromatolites represent forms that began to develop in an intertidal setting with the Holocene flooding of the Great Bahama Bank. The thrombolites, however, began to form under the present, normal-marine subtidal conditions. The eukaryotic stromatolites represent intermediate forms between prokaryotic stromatolites and thrombolites. There is evidence for a gradual change from stromatolite to thrombolite reefs associated with rising sea-level. With the deepening, there would have been a decrease in salinity, an increase in energy, and possibly an increase in nutrient supply; all factors that favor thrombolite growth. We propose that the co-existing stromatolites and thrombolites found off Lee Stocking Island did not grow contemporaneously, but reflect a response to changing environmental controls with changing sea-level.

Abiological origin of described stromatolites older than 3.2 Ga: Comment and Reply

Abiological origin of described stromatolites older than 3.2 Ga: Comment and Reply

Stromatolites Discovered in Nihewan Formation and Their Paleoenvironment

Columnar stromatolites have been discovered in two beds of the upper part of the Nihewan Formation, a series of lacustrine deposits. The structure of the stromatolites is characterized by alternation of light, intergranular pore-rich laminae and dark, organic substance-rich laminae. Abundant filamentous algal remains have been discovered in stromatolite laminae, some of them are similar to the species present on the shore of the Caribbean Sea that are living in warmer climate than in the Nihewan area now. With the ESR and U-series age methods, it has been determined that the ages of the lower and upper stromatolite beds are about 130,000 and 93,000 a B. P. , respectively. Compared with many other geologic events taking place during the period in Northern China, we conclude that the two stromatolite beds were formed during the two warmer stages of the Last Interglacial.

The Middle Proterozoic Purcell Supergroup in the Southwestern Rocky and Southeastern Purcell Mountains, British Columbia and the Initiation of the Cordilleran Miogeocline, Southern Canada and Adjacent United States

ABSTRACT Purcell Supergroup strata exposed in the southeastern Purcell and southwestern Rocky Mountains comprise a turbidite sequence (Aldridge Formation) gradationally overlain by shallow-water deposits. The lower member of the Kitchener Formation represents the transition from intertidal and shallow-subtidal clastic sedimentation of the Creston Formation to the shallow-subtidal shelf facies of the upper member. Varicoloured siltite and argillite of the Van Creek Formation mark the return to shallow-water clastic sedimentation. They are abruptly overlain by volcanic rocks and shallow-water clastic sediments of the Nicol Creek Formation. Stromatolitic dolomite and quartzite of the Sheppard Formation comformably to disconformably overlie the Nicol Creek Formation. The siltite and argillite comprising the Gateway Formation are interpreted as lagoonal deposits. The overlying subaerial quartzites of the Phillips Formation form a northward and westward thinning marker unit. The Roosville Formation, which forms the top of the Purcell succession, has been removed by pre-Devonian erosion over much of the area. The shallow-water deposits comprising the Creston through Phillips Formations can be subdivided into three composite stratigraphic units that are recognized throughout the northern Belt-Purcell basin. Thickness variations in the lower two units outline a north-trending basin margin that is deflected more than 200 km westward near 49°N latitude. The rectilinear shape can be ascribed to deeply rooted block faults developed during continental rifting. This shape governed the later development of a major structural re-entrant in the Rocky Mountain thrust and fold belt. Thickness variations in the upper unit record the evolution of epeirogenic structures that apparently controlled the distribution of volcanic rocks within the Belt-Purcell basin. A re-evaluation of middle and upper Belt-Purcell correlations indicates that the hypothesis of a 'dome' supposed to have formed during deposition of the lower Missoula Group was based on incorrect correlation.

Stromatolites and publishers' dishonesty

Stromatolites and publishers' dishonesty

Regressive Stromatolite Reefs and Associated Facies, Middle Goulburn Group (Lower Proterozoic), in Kilohigok Basin, N.W.T.: An Example of Environmental Control of Stromatolite Form

ABSTRACT The Goulburn Group is a thick succession of intracratonic sedimentary rocks deposited within the lower Proterozoic Kilohigok Basin, northwestern Canadian Shield, which have been correlated with strata of the Coronation Geosyncline and the Athapuscow aulacogen. The middle part of the Goulburn Group is comprised of mudstone, carbonate and stromatolitic carbonate rocks and is classified as the 'carbonate-mudstone stratigraphic interval' of the Kilohigok Basin. This interval of sedimentation can be subdivided into early and late stages. The late stage consists of a vertical succession of facies representing: basinal mudstone-dominated and carbonate-dominated environments, a shallow submarine shelf with clastic carbonate and thick mudstones, a complex stromatolite reef and associated stromatolite facies and intertidal-supratidal mudstone. These facies represent a diachronous sequence of once laterally juxtaposed environments which is interpreted to represent a major regression that affected the entire Kilohigok Basin. Stromatolite forms characterize different stratigraphic assemblages that correspond with changes in environmental conditions. Reconstruction of the lateral distribution of a now vertical succession of stromatolitic carbonates shows a basinward to landward pattern of: fore-reef clastics with subtidal stromatolite mounds, reef tract with large subtidal mounds and channeled columns, and a quiet-water back-reef with stromatolite biscuits. Stromatolite elongations are interpreted to define paleo-reef-tract trends.

Stromatolites Used to Determine the Time of Nearest Approach of Earth and Moon

Stromatolites Used to Determine the Time of Nearest Approach of Earth and Moon