Smaller Foraminifers Research Articles

Bashkirian foraminifera in the Sanandaj-Sirjan Zone (Iran): Their importance in taxonomy, biostratigraphy, and palaeobiogeographic reconstruction of the southern margin of Western Palaeotethys

A noteworthy Lower Pennsylvanian fusulinid fauna is, for the first time, reported from the Sanandaj-Sirjan Zone in Iran. From the main outcrop, eighty five species of thirty genera belonging to two classes, five orders, five suborders, seven superfamilies, sixteen families, and seven subfamilies are examined. The present fusulinids are assigned to the early–late Bashkirian (Syuranian, Akavassian, and Askynbashian substages). The characteristic taxa include Semistaffella spp., Plectostaffella varvariensis, Millerella marblensis, Pseudostaffella spp., Profusulinella cf. parva, and Ozawainella spp. Three successive assemblages spanning the early–late Bashkirian are proposed: (1) Assemblage with Semistaffella variabilis-S. minuscilaria-Plectostaffella seslavica (Syuranian age); (2) Assemblage with Pseudostaffella antiqua-P. compressa (Akavassian age); and (3) Assemblage with Ozawainella mosquensis-Profusulinella cf. parva (Askynbashian age). The new found fusulinid assemblages of the Sanandaj-Sirjan Zone have close resemblance and are well correlative with the Bashkirian standard and reference sections of the Russian Platform, Donets Basin, Urals, Southern Turkey, and Central Asia. The Iranian Bashkirian foraminiferal faunas, furthermore, exhibit very similar compositions to their counterparts in other areas of the Western Palaeotethys Region; many foraminifers, both smaller foraminifers and fusulinids, are in common between them. The new findings, in addition to clarifying the biostratigraphic correlation with the well-known type sections of the same age, are also important for reconstructing the palaeoposition of the Sanandaj-Sirjan Zone as a southern margin of Western Palaeotethys.

Sedimentary evolution and sea-level fluctuation of a Paleo-Tethyan Permian carbonate-dominated succession from central China

The Paleo-Tethys experienced major geographic, tectonic, climatologic, and environmental changes during the Permian. A newly documented and complete Permian carbonate-dominated succession (>3 km) in the Xikou section, Zhen'an, Shaanxi, central China provides a unique opportunity to record its depositional environment evolution, sea-level fluctuation, and associated paleogeographic and paleoclimatic perturbation of the eastern Paleo-Tethys. Field observation and petrographic analysis document eighteen facies and indicate evolutional facies of a carbonate ramp within the Xikou section. The vertical distribution of those facies in the Xikou section indicates a fluctuated sea-level during the Permian, which reflected the global climatic changes and was associated with eastern Paleo-Tethys evolution. The relatively low sea-level accompanied by high-frequency fluctuations during the Asselian to Artinskian may be related to the expansion of glaciation (P1 and P2), while the followed significant rising at Kungurian may reflect the major deglaciation of the Late Paleozoic Ice Age (LPIA). The abrupt falling of sea-level at the end of the Capitanian was globally synchronous and may be relevant to mid-ocean ridge spreading and superimposed with global cooling (P4), which was in accord with the skeletal grain replacement of the fusulinaceans and dasyclads by small foraminifers and Gymnocodium, and was considered as a major reason for Middle Permian Extinction. The early Wuchiapingian characterized by densely mixed sequences of carbonate and siliciclastic intervals had a highly frequent fluctuating sea-level, which may be influenced by high frequent short-term climatic variations. The sea-level falling after it reached its highest stand during the middle Wuchiapingian, was suggested as a far-field response to the expansion of the Permian glaciation episode P4, or as a result of a regional tectonic transition from extension to compression relevant to the eastern Paleo-Tethys evolution. In addition, the overall rising trend of the sea-level and the thick succession in the Xikou area suggest that the South Qinling belt was primarily under an extensional setting during the Late Carboniferous to Early Triassic, in response to Tethys rifting, which may imply the subduction of Mianlue Ocean was possibly beyond the Permian.

Biotic Response to Rapid Environmental Changes During the Permian–Triassic Mass Extinction

The divergent patterns of Permian–Triassic mass extinction (PTME) have been extensively documented in varying water depth settings. We here investigated fossil assemblages and sedimentary microfacies on high-resolution samples from two adjacent sections of the South China Block: Chongyang from shallow-water platform and Chibi from deeper-water slop. At Chongyang, abundant benthos (over 80%), including rugose corals, fusulinids, calcareous algae, and large foraminifers, disappeared precipitously at the topmost of Changxing Formation grainstone, which suggested complete damage of the benthic ecosystem, confirming a sudden single-pulse extinction pattern. The end-Permian regression, marked by a karst surface, provided a plausible explanation for this extinction pattern. Whereas for the fauna in Chibi, the benthos was relatively abundant (20%–55%) with more trace fossils and lacking calcareous algae. Benthic abundance in Chibi reduced by two steps at the two claystone beds (Beds 10 and 18): bioclastic content dropped from an average of 50% in Beds 1–9 to 10% in Beds 11–17 and then to less than 5% in Beds 19–23, suggesting a two-pulse extinction. At the first pulse, large foraminifers were prominent victims in both shallow- and deeper-water settings. A plausible survival strategy for small-sized foraminifers was to migrate to deeper water to avoid extreme heat in shallow water. The early Triassic transgression prompted some small foraminifers to migrate back to original platforms and flourish briefly as disaster forms. At the Early Triassic mudstone with bottom-water settings in Chibi, the appearance of abundant small pyrite framboids (diameters of 4.74–5.96 μm), an indicator of intensified oxygen deficiency, was simultaneous with the two-step reduction of benthic diversity and abundance. Thus, anoxic conditions might be the main cause of the PTME at deeper-water settings. Our study is an example of the wider debate about biotic response to rapid environmental change for both the Permian–Triassic transition and modern days.

New species of small foraminifers from the Mechetlino Quarry section (Southern Urals, Russia): a potential candidate for the GSSP of the lower boundary of the Global Kungurian Stage

New species of small foraminifers from the Mechetlino Quarry section (Southern Urals, Russia): a potential candidate for the GSSP of the lower boundary of the Global Kungurian Stage

First discovery of Wuchiapingian (Late Permian) foraminiferal fauna from the Zhari Namco area, central Lhasa Block, Tibet, and their palaeogeographic implications

A new foraminiferal fauna is reported from the upper part of the Xiala Formation in the Zhari Namco section in the central Lhasa Block, which contains three species of fusulines and 26 species of small foraminifers. The presence of Reichelina and Codonofusiella in the fauna suggests a Wuchiapingian age. A review of the Lopingian faunas in several localities in the Lhasa Block indicates that this block was under a shallow marine environment during the Lopingian, rather than an uplifted terrestrial environment as previously recognized. The Lopingian palaeobiogeography as well as the sequences of the Lhasa Block differs greatly from the adjacent South Qiangtang, Karakorum and South Pamir blocks, and the Tethys Himalaya region of the Indian Plate. It further suggests that the Lhasa Block was separated from the South Qiangtang Block in the north by the Bangong‐Nujiang Ocean and the Tethys Himalaya area in the south by the Neotethys Ocean during the Lopingian time. Furthermore, the dissimilarity of the Guadalupian and Lopingian strata and faunas between the Lhasa and Karakorum blocks and similarity between the Lhasa and Tengchong blocks, may suggest that the Lhasa and Tengchong blocks were linked together during the Permian.

Distinguishing Late Holocene Storm Deposit From Shore-normal Beach Sediments From the Gulf of Thailand

Grain size, as one of sedimentological proxies, coupled with a detailed description of the sedimentary structures and luminescence dating were used to unveil the sediment sources and transport process of the Holocene ancient coastal storm events recorded in the beach ridge plain, wet swale and muddy environments at Prachuap Khiri Khan, in the Southern Peninsula of Thailand. In this study, a total of 141 sand samples were collected from the shore-normal ridge-swale topography and analyzed for layers of candidate storm deposits, revealing at least 21 candidate coastal storm events. The grain size distribution of beach sediments was, in general, unimodal, while the candidate storm sediments revealed a mixed combination of multimodal, bimodal and unimodal distributions. Plots of mean grain size against skewness and kurtosis and of skewness against kurtosis could differentiate storm deposits from shore-normal beach sediments. Sedimentary structures preserved in the ancient coastal storm deposits included parallel and inclined landward laminations, mud rip-up clasts, layers of shell fragments, a pebble grain, normal and reverse grading and sharp lower and upper contacts. Candidate storm layers overlain on a dry beach ridge intervened with mud in a swale showed a finer and thinner landward deposit. Marine shell fragments, smaller foraminifers, ostracod and scaphopod (tusk shell), were well preserved. Based on optically stimulated luminescence dating and a correlated accelerator mass spectrometry age, multiple layers of sand derived from different frequencies of coastal storms were deposited over the middle to late Holocene.

Biostratigraphy of the Paleogene of Syria Based on Small Benthic Foraminifera

Information on the taxonomic composition and stratigraphic distribution of small benthic foraminifers in the Danian–Priabonian Paleogene stages of Syria based on the analysis of V.A. Krasheninnikov’s collections is presented. The small benthic foraminiferal zones identified in the Palmyrid sections within the framework of planktonic foraminiferal zonation developed by Krasheninnikov and correlated with the zonal standard of the International Stratigraphic Scale (zones P1–P17) are the following: Stensioeina beccariiformis–Anomalina danica Zone (P1a–P2); Vaginulina robusta–Pyramidina crassa Zone (P3); Reussella paleocenica Zone (P4–P5); Pseudogaudryina soldadoensis–Cibicidoides lybicus Zone (P6–P7); Hydromylinella wittpyuti Zone (P8–P9); beds with Paragaudryina dalmatina–Hydromylininella wittpyuti (P10 and P11); Falsoplanulina ammophila Zone (P12 and P13); beds with Queraltina epistominoides (P14); and Planulina costata Zone (P15–P17). The presence of species from these zones in other regions of Syria and Egypt is inferred from Krasheninnikov’s published works. The composition and development of the Paleogene foraminifera of Syria and the Crimean-Caucasian region that represent the Tethys and northeastern Peri-Tethys biota, respectively, are compared.

A robust calibration of the clumped isotopes to temperature relationship for foraminifers

The clumped isotope (Δ47) proxy is a promising geochemical tool to reconstruct past ocean temperatures far back in time and in unknown settings, due to its unique thermodynamic basis that renders it independent from other environmental factors like seawater composition. Although previously hampered by large sample-size requirements, recent methodological advances have made the paleoceanographic application of Δ47 on small (<5 mg) foraminifer samples possible.Previous studies show a reasonable match between Δ47 calibrations based on synthetic carbonate and various species of planktonic foraminifers. However, studies performed before recent methodological advances were based on relatively few species and data treatment that is now outdated. To overcome these limitations and elucidate species-specific effects, we analyzed 14 species of planktonic foraminifers in sediment surface samples from 13 sites, covering a growth temperature range of ∼0–28 °C. We selected mixed layer-dwelling and deep-dwelling species from a wide range of ocean settings to evaluate the feasibility of temperature reconstructions for different water depths. Various techniques to estimate foraminifer calcification temperatures were tested in order to assess their effects on the calibration and to find the most suitable approach.Results from this study generally confirm previous findings that there are no species-specific effects on the Δ47-temperature relationship in planktonic foraminifers, with one possible exception. Various morphotypes of Globigerinoides ruber were found to often deviate from the general trend determined for planktonic foraminifers.Our data are in excellent agreement with a recent foraminifer calibration study that was performed with a different analytical setup, as well as with a calibration based exclusively on benthic foraminifers. A combined, methodologically homogenized dataset also reveals very good agreement with an inorganic calibration based on travertines. Our findings highlight the potential of the Δ47 paleothermometer to be applied to recent and extinct species alike to study surface ocean temperatures as well as thermocline variability for a multitude of settings and time scales.

Multidisciplinary study of the Mechetlino Quarry section (Southern Urals, Russia) — The GSSP candidate for the base of the Kungurian Stage (Lower Permian)

The Mechetlino Quarry section is a potential candidate for the Global Section Stratotype and Point (GSSP) for the base of the Global Kungurian Stage on the International Stratigraphic Chart. In 2017, the Mechetlino Quarry section became the part of the First Geopark in Russia, therefore excavation work was carried out to clear it, a road was laid, and infrastructure was developed. Recent evidence to justify the base Kungurian boundary in the Mechetlino section was obtained. Additional conodonts confirmed the data of V.V. Chernykh on the Artinskian–Kungurian transition. Besides Neostreptognathodus pnevi Kozur and Movshovitsch, the second marker (N. lectulus Chernykh) of the base-Kungurian was established. The Artinskian–Kungurian transition of the Mechetlino Quarry section is characterized by the richest associations of small foraminifers, ammonoids, and other groups. The occurrence of mass Clausiuraloceras above the Kungurian boundary, which changed the representative Artinskian association, was identified. Small foraminifers of the Artinskian–Kungurian transition are numerous and include sufficient species to provide a correlation with Western Tethys, Svalbard and Australia. Data on isotopic ratios of δ13C and δ18O, δ13Corg values and the magnetic susceptibility were obtained for the first time.

Evidence of warm climate during late Sakmarian–early Artinskian in Posht‐e Badam Block, Central Iran and its paleogeographic implication

Examination of the geochemical data, faunal associations, and bauxite/laterite horizons in the Khan Formation, in Kalmard area, Posht‐e Badam Block, Central Iran are presented. The data provide insights on the paleogeographic position of Central Iran as part of the Cimmerian during the late Sakmarian–early Artinskian time. Bauxite/laterite as valuable warm and humid paleoclimate proxies are observed in all studied sections of the mixed siliciclastic‐carbonate Khan Formation and are meters to tens of meters thick. The warm and humid climate is also verified by the previous studies of Khan Formation sandstones yielding high chemical weathering and highly mature quartz grains. Plant fossils recovered from these sandstones are further evidence of the warm and wet climate. The results of the geochemical studies of the Khan Formation carbonates are in robust agreement with the inferred paleoclimate condition from bauxite/laterite horizons and sandstone studies of the Khan Formation. The bivariate plot of major and minor elements shows that aragonite as an indicator of warm water conditions was the major carbonate mineralogy of the Khan Formation limestones. Temperature calculation based on the heaviest oxygen isotope value of the least‐altered sample indicates that the temperature was around 36 and 29 °C for dolomites and limestones of the Khan Formation, respectively. The skeletal grains of the Khan Formation limestones are representative of a photozoan association with fusulinids, smaller foraminifers, calcareous algae, and common crinoids, brachiopods and bryozoans and also ooids and peloids as non‐skeletal grains. Therefore, the results of this study are not in agreement with previous fusulinid‐based paleogeographic interpretations, which suggested a high‐latitude paleoposition for the Posht‐e Badam Block and its separation from other Central Iran terrains during the late Sakmarian–early Artinskian. These data indicate that Posht‐e Badam Block was part of Central Iran during the late Sakmarian–early Artinskian, and its paleoposition was at a low paleolatitude.

Sea level drop, palaeoenvironmental change and related biotic responses across Guadalupian–Lopingian boundary in southwest, North and Central Iran

AbstractThe Capitanian to Wuchiapingian deposits in Zagros (southwest Iran), Alborz (North Iran) and Central Iran display important information about the end-Guadalupian extinction. According to lithological characteristics in the studied sections, the Guadalupian–Lopingian boundary (G-LB) interval can be subdivided into three units: the Capitanian unit, the latest Capitanian unit or interval unit (i.e. deposits in the topmost portion of the Capitanian strata) and the Wuchiapingian unit. The G-LB horizon is set at the base of Wuchiapingian deposits based on the first appearance datum (FAD) of the Late Permian diagnostic small foraminifers. The Capitanian unit was deposited subtidally, but the latest Capitanian unit was in the intertidal zone. The Wuchiapingian unit shows the return of subtidal conditions. A remarkable subaerial exposure occurs at the top of the Ruteh Formation, in Alborz, which is a laterite/bauxite horizon followed by continental deposits. The overall facies change in the G-L boundary intervals in the sections under study indicates a sea level drop around the G-LB which was at its lowest level in the Ruteh section. The decline and elimination of shallow marine biota in the G-LB interval took place in two steps in the Zagros and Alborz sections and in one step in Central Iran. These are indicative of the appearance of the stressful environment during the late Capitanian shallowing trend before the G-LB. The sea level drop and regression in the late Capitanian can be considered the major causes of end-Guadalupian extinction in the Iranian sections, but in the Alborz area volcanic activity is another feasible cause of this crisis.

Permian smaller foraminifers: taxonomy, biostratigraphy and biogeography

Abstract This review has been undertaken in order to present some interpretations about the biostratigraphy of the smaller foraminifers belonging to four classes present during the Permian: Fusulinata, Miliolata, Nodosariata and Textulariata. Biostratigraphic markers of these classes are principally known in the orders and superfamilies of Lasiodiscoidea, Bradyinoidea and Globivalvulinoidea (Fusulinata), Cornuspirida (Miliolata), and in the entire class Nodosariata. The class Textulariata is too little known during the Permian to play a significant biostratigraphical role: nevertheless, the appearance of the order Verneulinida is probably an important bioevent. The main genera among the lasiodiscids are Mesolasiodiscus , Lasiodiscus , Lasiotrochus , Asselodiscus , Pseudovidalina , Xingshandiscus and Altineria ; the bradyinoids Bradyina and Postendothyra ; the globivalvulinoids Globivalvulina , Septoglobivalvulina , Labioglobivalvulina , Paraglobivalvulina , Sengoerina , Dagmarita , Danielita , Louisettita , Paradagmarita , Paradagmaritopsis and Paremiratella ; the miliolates Rectogordius , Okimuraites , Neodiscus , Multidiscus , Hemigordiopsis , Lysites , Shanita and Glomomidiellopsis , and the tubiphytids and ellesmerellids, which might be specialized miliolate and cyanobacterium consortia, with reference to microstructures and phylogenies of these groups. The Nodosariata markers belong to Nodosinelloides , Tezaquina , Polarisella , Geinitzina , Pachyphloia , Rectoglandulina , first true Nodosaria , Langella , Pseudolangella , Calvezina , Cryptoseptida , Cylindrocolaniella , Colaniella , Frondina and Ichthyofrondina , but their lineages are too poorly understood to permit an accurate biostratigraphic use at the present time. The superfamily Geinitzinoidea is emended. Finally, palaeobiogeographical implications based on Shanita , Colaniella and Altineria are given.

Redox conditions across the G–L boundary in South China: Evidence from pyrite morphology and sulfur isotopic compositions

The end-Guadalupian (middle Permian) mass extinction recorded the disappearance of shelf faunas such as fusulinids, small foraminifers, brachiopods, rugose corals which flourished in the warm shallow marine habitats after the late Pennsylvanian–early Permian glaciation. The causes for this mass extinction are still unclear. Marine anoxia, often as a cause for other mass extinctions, has been paid less attention in this extinction. Here we present a comprehensive study including pyrite morphology and sulfur isotopic compositions of pyrite across the Guadalupian–Lopingian (middle–upper Permian; G–L) boundary at Tianfengping in northern Yangtze Platform and at Penglaitan in southern Yangtze Platform in South China. Our results show that the sulfur isotope ratios of pyrite mainly track the framboid size distributions in these two sections. Anoxia and intermittent euxinia occur at the G–L boundary evidenced by the coincidence between reduction of framboid size and the extremely negative sulfur isotope values of pyrite involving disproportionation, and corresponds to the main mass extinction of the end-Guadalupian, suggesting a causal link between them. Long-term dysoxic conditions during the middle Capitanian are evidenced by the relative small framboid size and lower sulfur isotope ratios of pyrite, and coincide with the first pulse of the end-Guadalupian mass extinction, also suggesting a causal link between them. The oxygen-depletion conditions in the Capitanian during the global sea level falling may be the main cause for the end-Guadalupian mass extinction.

THE EVOLUTIONARY DEVELOPMENT OF GLOBIVALVULINA SPECIES AND THEIR STRATIGRAPHIC DISTRIBUTION IN UPPER PERMIAN SEDIMENTS OF THE KUSHAKOUL CANYON, IN HIGH ZAGROS, IRAN: WITH A REVIEW OF THEIR SITUATION IN BIOSTRATIGRAPHY OF DALAN FORMATION

The subfamily of Biseriammininae includes genera that have kind of great species diversity in the sediments of Upper Permian in the most parts of Iran, particularly Zagros Mountains. As the complete section of Upper Permian sediments is exposed in the Zagros basin, the Oshtoran-kuh region has been selected of this study. Sections of the different genera have been drawn by camera Lucida instrument and species have been differentiated based on the structural properties of the shell. Generally, 24 species of Globivalvulina genus, 8 species of Paraglobivalvulina genus and 1 species of Paraglobivalvulinoides genus have been identified and the evolutionary pattern of these genera and their species are presented. In addition, biostratigraphic studies of revealed ten biozones based on the fuzolinids and small foraminifers identified in Dalan Formation in Zagros basin, Iran.

Paleocene and Lower Eocene sections in the southern part of the Crimean Peninsula

This work summarizes updated data on Paleocene and Lower Eocene deposits of the Crimean Peninsula concerning the systematics of assemblages of small foraminifers (and partly data on other microfossils) and results of biostratigraphic subdivision of sections. It is shown that Lower Paleocene and Lower–Middle Eocene deposits accumulated during two cycles of carbonate sedimentation in a warm-water shallow basin. These deposits are separated by Upper Paleocene deep-water deposits. The systematic composition of foraminifers testifies that there were different facies conditions in different parts of the Crimean basin and its connection to Western European and Tethyan basins during the Paleocene–early Eocene.

Lower Permian smaller foraminifers from the Rahdar section, Central Iran

Smaller foraminifers from the Chili Formation recovered in the Rahdar section of the Kalmard tectonic block west of Tabas, Central Iran, are studied. Two smaller foraminiferal assemblages whose position in the section completely coincides with that of previously encountered Kalaktash and Halvan fusulinid complexes are recognized. The age of these Deckerella elegans-Nodosinelloides pinardae and Howchinella sossipatrovae assemblages is Sakmarian and late Sakmarian-early Artinskian (?), respectively. A new species Hemigordius rahdarensis Filimonova, sp. nov. is described.

High amplitude redox changes in the late Early Triassic of South China and the Smithian–Spathian extinction

The Early Triassic was a time of remarkably high temperatures, large carbon cycle perturbations and episodes of widespread ocean anoxia. The sediments in the Nanpanjiang Basin of South China provide superb opportunities to examine the sedimentary response to these extreme conditions especially during the crisis interval at the Smithian-Spathian (S-S) boundary. We have investigated a deep water section at Jiarong and a shallower water section at Mingtang. These contain a range of including black shales, micritic limestone units and rudaceous carbonate event beds that include flat pebble conglomerates and breccia debrites that bear similarities to the hybrid event beds seen in clastic turbidite successions.Redox proxies (pyrite framboids and trace metals) reveal that widespread anoxia in the late Smithian persisted into the Novispathodus pingdingshanensis Zone of the early Spathian before a sharp transition to highly oxygenated griotte facies (red marine strata) in the Icriospathodus collinsoni Zone that records an oxic rebound. Benthic faunas are locally common but of low diversity and dominated by thin-shelled bivalves and ostracodes with small foraminifers and exceptionally rare fish remains. Bioturbation was intense only in the early-middle Spathian (I. collinsoni conodont zone) Griotte facies. Anoxia and extremely high temperatures probably played a role in severely restricting the abundance of fish and the small sizes of marine invertebrates at this time. The presence of ooids and seafloor fan cements in our study sections indicates highly saturated conditions rather than acidification at the end of the Smithian.

Cisuralian series of the Permian System of the southeastern Sol-Iletsk Swell: Biostratigraphy and lithology

This paper discusses the results of the study of the carbonate beds of the Cisuralian Series of the Permian System in the Sol-Iletsk Swell near the merging point of the Cisuralian Foredeep and the Peri-Caspian Depression. Assemblages of fusulinids and smaller foraminifers are studied in the boreholes. Seven biostratigraphic subdivisions (beds with fauna) are recognized for the upper Artinskian-lower Kungurian interval and microfacies are studied in great detail. The carbonate succession is lithostratigraphically subdivided and patterns in facies distribution are revealed at the upper Artinskian-lower Kungurian boundary.

Microbialite concretions in a dolostone crust at the Permian–Triassic boundary of the Xishan section in Jiangsu Province, South China

Carbonate concretions with structures and fossil groups associated with microbialite developed in a dolostone crust at the Permian–Triassic boundary of the Xishan section in Jiangsu Province, South China. These structures include clotted fabrics and laminated carbonate needles, as well as abundant carbonate crystal fans. Fossil groups associated with microbialite include microconchids, small gastropods, and small foraminifers. These fabrics and fossils suggest that the concretions are carbonate microbialite blocks developed in the dolostone crust. On the basis of the analysis of the microfabrics and the fossil groups together with a comparison to modern analogues, we attribute the formation of the micritic patches in the microbialite concretions to the calcification of cyanobacterial mats via carbonate nanoparticles and we attribute the carbonate crystal fans to the direct recrystallization of micritic carbonates. The sparitic patches were interpreted as either the direct recrystallization of micritic carbonates or the precipitation of carbonate spars in the inter-/intra-spaces of metazoan shells together with the recrystallization of these shells. The similarities to modern stromatolites, both in morphology and in internal texture, suggest that the laminated carbonate needles are stromatolite laminae built by filamentous cyanobacteria. The preservation of these microbialite microfabrics indicates that early lithification by carbonate precipitation was widespread and intense following the end-Permian boundary events. The weak development of microbialites as small concretions may be attributed to the deeper water depth and the lower water energy in the Xishan area during the earliest Triassic.

Some contrasting biostratigraphic links between the Baker and Olds Ferry Terranes, eastern Oregon

New stratigraphic and paleontologic data indicate that ophiolitic melange windows in the Olds Ferry terrane of eastern Oregon contain limestone blocks and chert that are somewhat different in age than those present in the adjacent Baker terrane melange. The melange windows in the Olds Ferry terrane occur as inliers in the flyschoid Early and Middle Jurassic age Weatherby Formation, which depositionally overlies the contact between the melange-rich Devonian to Upper Triassic rocks of the Baker terrane on the north, and Upper Triassic and Early Jurassic volcanic arc rocks of the Huntington Formation on the south. The Baker terrane and Huntington Formation represent fragments of a subduction complex and related volcanic island arc, whereas the Weatherby Formation consists of forearc basin sedimentary deposits. The tectonic blocks in the melange windows of the Weatherby Formation (in the Olds Ferry terrane) are dated by scarce biostratigraphic evidence as Upper Pennsylvanian to Lower Permian and Upper Triassic. In contrast, tectonic blocks of limestone in theBaker terrane yield mostly fusulinids and small foraminifers of Middle Pennsylvanian Moscovian age at one locality.Middle Permian (Guadalupian) Tethyan fusulinids and smaller foraminifers (neoschwagerinids and other Middle Permian genera) are present at a few other localities. Late Triassic conodonts and bryozoans are also present in a few of the Baker terrane tectonic blocks. These limestone blocks are generally embedded in Permian and Triassic radiolarian bearing chert or argillite. Based on conodont, radiolarian and fusulinid data, the age limits of the meange blocks in the Weatherby Formation range from Pennsylvanian to Late Triassic.