Ordovician Cephalopod Biofacies of South China and Its Provincialization

The research on biofacies and its provincialization is of important significance not only for the increasing of precision of stratigraphic subdivision and correlation in South China, the reconstruction of ancient environment and paleogeography and even the guiding of oil and gas exploration, but also for the study of paleobiogeogrphy and sea level changes of southern China in Ordovician. On the basis of the studies of the ecological characteristics of Ordovician cephalopods from South China, eighteen cephalopod biofacies are recognized and described ： （1） Open platform Proterocameroceras biofacies ; （2） Restricted platform Pseudoectenolites-Xiadongoceras biofacies; （ 3 ） Open platform Retroclitendoceras- Pararetroclitendoceras biofacies; （4） Open platform Pronajaceras-Mamagouceras biofacies ; （5） Shelf slope-basin Cyclostomiceras biofacies; （6） Open platform Cameroceras-Cyrtovaginoceras biofacies; （7） Open platform Coreanoceras-Manchuroceras biofacies; （8） Shelf slope-basin Kaipingoceras- Kyminoceras biofacies; （9） Inner shelf Bathmoceras-Protocycloceras biofacies; （10） Middle shelf Dideroceras-Ancistroceras biofacies; （11） Deep-water shelf Lituites-Cyclolituites biofacies ; （12） Stag- nant basin Lituites-Trilacinoceras biofacies; （13） Deep-water basin Paraendoceras-Sactorthoceras biofacies; （14） Deep-water shelf Sinoceras-Michelinoceras-Disoceras biofacies; （15） Deep-water shelf Beloitoceros-Jiangshanoceras biofacies; （16） Deep-water shelf-basin Eurasiaticoceras biofacies; （ 17 ） Shelf-slope Jiangxiceras-Yushanoceras biofacies; （18） Deep-water basin Michelinoceras biofacies. The cephalopods of these biofacies, their ecological characteristics, and living conditions are elucidated in this article. The association law of cephalopod biofacies in time and space shows that there were three cephalopod biofacies provinces in South China during the Ordovician, i.e. , Yangtze biofacies province, East Guizhou （贵州）-West Hunan （湖南） biofacies province （mixed-type biofacies province）, and Central Hunan-West Zhejiang （浙江） biofacies province. It is suggested that differentiation of cephalopod biofacies was mainly controlled by sea level changes and tectonic evolution. The differentiation is obvious during lower sea level and not developed during high sea level.

Late Permian- Early Triassic Conodont Biofacies and Bioprovinces in South China and Himalaya

On the basis of existing conodont data, the authors have studied the Late Permian-Early Triassic conodonts of different forms and biofacies in detail. Five conodont biofacies are recognized, from shallow to deep waters 1. Hindeodus conodont biofacies, 2. Pachycladina-Parachi rognathus conodont biofacies, 3. Gondolella -Hindeodus conodont biofacies, 4. Gondolella-Neospathodus conodont biofacies, and 5. Xaniognathus conodont biofacies. Considering the temporal and spatial changes of these conodont biofacies, 3 conodont bloprovinces have been divided. In light of the biofacies changes of each bioprovince, the authors also discuss, in this paper, the regularity of transgression-regression cycles of eastern Tethys and their possible relation to the mass biotic alternation.

Foraminifera in Cenozoic Paleoenvironments

Paleontologists search the fossil record for evidence of age, ancient environments, phylogenetic reconstructions and ancient communities. Cenozoic foraminifera preserve evidence for all of these simultaneously from the water column and from at, above and below the sediment/water interface. As our understanding of foraminiferal assemblages and their place in the strata （biofacies） becomes more sophisticated, so are foraminiferal biofacies challenged to contribute to more subtle problems in Cenozoic earth and life history. Progress is described as a series of five ＂integrations＂. （Ⅰ） The quantification of foraminiferal biofacies was an advance on simple presences and absences of species meeting such questions as marine or nonmarine, or shallow or deep. （Ⅱ） Foraminiferal shells carry geochemical signals especially isotopes of oxygen （temperature, ice volume）, carbon （nutrition and the carbon cycle）, and strontium （seawater ratios through time）. （Ⅲ） From modern foraminiferal biology we have lifestyle insights leading to a model of oceans and paleo-oceans called the trophic resource continuum, a valuable way into greenhouse-icehouse comparisons and contrasts. （Ⅳ） Biofacies changes in space and time are sometimes abrupt with little evidence of diachrony, and sometimes gradual. These patterns are clarified in the context of sequence stratigraphy （which they enrich in turn）. （Ⅴ） The paleobiological counterpart of sequence stratigraphy is evolutionary paleoecology, reconstructing communities in deep time. The foraminifera are perfectly suited to investigate the possibility （or likelihood） that global environmental shifts have controlled community turnover in the pelagic, neritic and terrestrial realms.

Characterization of the Upper Cretaceous Sediments in the Ikpankwu-Ihube Axis, Okigwe, Southeastern Nigeria

Detailed characterization of the outcropping sediments in the Ikpankwu and Ihube axis was undertaken to validate lithostratigraphic boundaries and nomenclatures which had stirred up debates amongst scholars in recent times. Stochastic method established dominant facies associations and preferred stacking patterns, which were used to interpret environments of deposition (EODs), while foraminiferal and palynological analyses fingerprinted both paleo depths and age of the sediments. The results established the dominance of similar lithofacies at the basal parts of both sections indicating mappable geological units and members of the same lithostratigraphic unit. The basal lithofacies are succeeded up section, however, by different lithological units in both the KM 75 and Ikpankwu sections. Interpretations of EODs using lithofacies successions predicted fluvial to tidally-influenced shallow marine deposits, which are environments in close affinity with each other. Interpretations using abundance and diversity of micro fauna supported non-marine (coastal-deltaic) to middle neritic paleo-water depths also, typical of marginal to shallow marine EODs. Recovered foraminiferal assemblages in the shale samples from the upper parts of both sections, however, depicted deposits of Nsukka Formation despite variations observed in lithofacies assemblages because the identified Haplophragmoides species that populate the upper units had been used to define the Late Maastrichtian-Paleocene age. Sediments at the basal parts with mappable lithological units at both sections were rather populated by species that connote the Campanian-Maastrichtian age when the Mamu Formation sediments were deposited. Palynomorphs recovered from both the basal and upper sections also suggested Campanian-Maastrichtian and Late Maastrichtian-Paleocene age, indicative of Mamu and Nsukka Formation sediments, respectively.

Facies analysis and palaeoecology of the Jurassic Spiti Shale Formation in the Spiti area,Northern India

The Spiti Shale Formation is a widely distributed stratigraphic unit of the passive northern margin of the Indian craton,deposited between the Callovian and earliest Cretaceous.The siliciclastic strata are dominated by dark-grey to black argillaceous silt.As the formation has undergone intense tectonic stress involving folding and faulting,it is very difficult to document a complete section.In the type area,the Spiti Valley,six sections have been measured that document parts of the three informal members of the formation,the Lower,Middle,and Upper members.Despite its uniform appearance,eight facies/biofacies types could be distinguished,ranging from the anoxic shale facies,with ammonites and belemnites as the only faunal elements,to the dysoxic Malayomaorica and Bositra biofacies,and the oxic to anoxic offshore shelf facies,which are characterized by low-diversity macrobenthos associations.Other facies are the condensed glauconiticphosphoritic mudrock facies and the Fe-oolitic siltstone facies(both characterized by sediment starvation),the aerated argillaceous silt-sandstone facies,and the tide-influenced nearshore shelf facies.The benthic macrofauna represents four bivalve-dominated associations all characterized by a very low to low species diversity.They are the Bositra buchii,the Australobuchia spitiensis,the Palaeonucula cuneiformis-Pruvostiella hermanni-Indogrammatodon egertonianus,and the Malayomaorica sp.-Australobuchia spitiensis-Retroceramus haasti association.Sediments and macrobenthic associations indicate that the Spiti Shale Formation represents outer to inner shelf environments,which for much of the time were subjected to upwelling and anoxic to dysoxic conditions.Distinct shallowing at the top characterizes the transition to the overlying Lower Cretaceous Giumal Formation.

Conodont Biostratigraphy of Ordovician Deep-Water Turbiditic Sequences in Eastern Australia——A New Biozonal Scheme for the Open-Sea Realm

Ordovician conodonts representing 28 genera and 28 named and three unnamed species were identified from 740 chert and siliceous siltstone spot samples(>3000 thin sections)from deep-water turbiditic sequences of the Lachlan Orogen in central and southern New South Wales,Australia.Based on these faunas,a new conodont biozonal scheme has been established to divide the Ordovician turbiditic successions of the Lachlan Orogen into 12 superbiozones and biozones.They are(in ascending order)the Paracordylodus gracilis Superbiozone(including the Prioniodus oepiki Biozone),Periodon flabellum Superbiozone(including the Oepikodus evae Biozone in the lower part),Periodon hankensis Biozone,Periodon aculeatus Superbiozone(including the Histiodella labiosa,Histiodella holodentata,Histiodella kristinae,Pygodus serra and Pygodus anserinus biozones)and the Periodon grandis Biozone.The Pygodus anserinus Biozone is divided further into the lower and upper subbiozones.This new conodont biozonation scheme spanning the upper Tremadocian to middle Katian interval permits precise age-dating and correlation of deep-water siliciclastic rocks that characterize the Ordovician Deep-Sea Realm regionally and internationally.

Sedimentary and environmental history of the Late Permian Bonikowo Reef(Zechstein Limestone, Wuchiapingian), western Poland

The Bonikowo Reef occurs in the central part of the Zechstein Limestone Basin in western Poland and was growing on the topmost edges of tilted blocks and/or on the top of uplifted horsts of the BrandenburgeWolsztynePogorzela High. Its size is ca. 1.6 km^2. The Bonikowo Reef shows the thickest reef section（90.5 m） recorded in the High. The Zechstein Limestone unit is represented mostly by limestones, often thoroughly recrystallized, although the macrotextures and biota of the boundstone are identifiable in most cases. The drillcore section is a mixture of boundstones（microbial and bryozoan）, wackestones, packstones and grainstones, which often co-occur. The δ^13 C and δ^18 O values for both calcite（avg. 3.8 ± 0.8‰ and-3.4 ± 1.7‰, respectively） and dolomite（avg. 3.5 ± 0.7‰ and-5.2 ± 1.3‰, respectively） are transitional between the values previously reported for condensed sequences of the basinal facies and larger reef complexes. The biofacies of the Bonikowo Reef are very similar to those recognized in other reefs of the BrandenburgeWolsztynePogorzela High, which owe their origin to the destruction of bryozoan boundstones. The biota composition is typical and characteristic of other Zechstein Limestone reefs. However, the Bonikowo Reef demonstrates the importance of microbialites, laminar and nodose encrustations, in the growth and cohesion of the Zechstein Limestone reefs. Such encrustations abound within the Zechstein Limestone although, in many cases, the real nature of the encrustations is difficult to ascertain. These laminated encrustations show great similarity to Archaeolithoporella that is one of the most important Permian reefbuilding organisms. The encrustations considered to represent Archaeolithoporella were also previously recorded in the Zechstein Limestone of western Poland and in its stratigraphic equivalent, the Middle Magnesian Limestone of Northeast England. The lower part of the sequence shows great biofacies variability that reflects common environmental changes. The major part of the section is represented by slope depositsgrading upward into the reef, which reflects the prograding nature of reef margin. The progradation rate for the Bonikowo Reef is estimated at 400 m/My.