Late carboniferous to early permian brachiopod faunas from the Bachu and Kalpin areas, Tarim Basin, NW China

Late Carboniferous and Early Permian brachiopod faunas are described from the Xiaohaizi section of the Bachu area and the Shishichang section of the Kalpin area, the Tarim Basin, NW China. Biostratigraphic studies of brachiopods and associated microfossils indicate that the Xiaohaizi Formation is Moscovian (Late Carboniferous) and the Shishichang Formation is Kasimovian-Gzhelian (Late Carboniferous), whereas the Nanza and Kankarin Formations are Asselian to early Artinskian (Early Permian). Two new species proposed from the Nanza Formation are Kutorginella tarimensis and Phricodothyris? bachuensis.

Late Paleozoic depositional history of the Tarim basin, northwest China: an integration of biostratigraphic and lithostratigraphic constraints

This study provides the first detailed lithostratigraphic and biostratigraphic constraints for improving stratigraphic resolution for hydrocarbon prospecting and exploration in the Tarim basin. A total of 49 stratigraphic units (38 formations and 11 members), ranging in age from the latest Devonian to Permian, are reviewed or redefined in terms of nomenclatures, lithology, age constraints, and lateral distributions based on the detailed field works or newly published data. Of these, the Piqiang Formation (new formation) is proposed to include the reefal carbonates of Asselian-Sakmarian age from the northern Tarim. The subsurface upper Paleozoic stratigraphic framework of the desert areas of the basin is also established for the first time. The high-resolution, basinwide stratigraphic correlations reveal that the sedimentation of the basin in the late Paleozoic was extremely uneven. Of these, the Famennian to Changhsingian successions are completely recorded in the south-western margin areas of the basin. Here, five eustatic sedimentary cycles are well recognizable, suggesting the sedimentation was more eustatically controlled and little affected by local tectonism. The late Paleozoic successions of both Kalpin and Taklimakan regions are commonly interrupted by major hiatuses at various horizons, suggesting that the sedimentation was apparently modified by local tectonism. Of these, the northward movement of the Tarim block and its subsequent collision with the Yili microcontinent (part of the Kazakhstan plate) may be principally accountable for the discrepancy in the sedimentation of the various regions in the basin in the late Paleozoic.

Internal structure and paleoecology of the lower Permian Uzunbulak reef complex of the Tarim Basin, Northwest China

The internal construction and biotic communities of the Uzunbulak reef of the northwestern Tarim Basin are studied for the first time. The reef was built during the Sakmarian, while the reef substrate and capping beds are of latest Asselian and earliest Artinskian ages, respectively. The reef substrate beds are composed of skeletal and oncoid grainstone. Those fusulinid-dominated skeletal shoals and oncoid banks indicate a high-energy environment and produced local topographic highs on which the reef grew. Reef framework consists mainly of calcisponge bafflestone, calcisponge-Thartharella framestone, and Tubiphytes, Archaeolithoporella and Girvanella boundstones. Calcisponges were the primary frameconstructors that baffled high-energy currents. Archaeolithoporella, Tubiphytes, Girvanella and possibly microbes acted as the primary binders for the boundstone framework. Fusulinids and brachiopods were common reef dwellers. The interreef facies sediments are composed of skeletal-crinoid wackestone-packstone. Most of bioclasts have thick, micritized envelopes. The back-reef facies deposits consist of alternating skeletal packstone to wackestone and black shale. Sea-level fluctuations were probably accountable for the reef growth and demise.

Of the reefal dwellers, brachiopods are extraordinarily abundant in Uzunbulak. They are assignable to five distinctive associations, one each from the reef substrate, framework and inter-reef facies, respectively, and two from the reef capping facies. The brachiopods in the substrate beds were mostly attached to hard substrates by a pedicle, while a few species rested on soft substrates by support of halteroid spines. Cementation of the ventral valve on hard substrates characterizes attachment of the reef framework brachiopods. All inter-reef species were anchored into the substratum comprising hard material by a strong pedicle. Back-reef brachiopods dominantly rested on the soft substrates by support of halteroid spines. the framework brachiopods had the strongest wave-resistant capability;those from both substrate and inter-reef facies were moderately capable of withstanding agitation; and the backreef species preferred to live in calmwater, organic-rich muddy environments.

Artinskian-Kungurian (Early Permian) brachiopod faunas from the Tarim Basin, Northwest China, part 1: biostratigraphy and systematics of productida

Late Palaeozoic sequence stratigraphy and brachiopod faunas of the Tarim Basin, Northwest China

This thesis deals with the stratigraphy and brachiopod systematic palaeontology of the latest Devonian (Famennian) to Early Permian (Kungurian) sedimentary sequences of the Tarim Basin, NW China. Brachiopod faunas of latest Devonian and Carboniferous age have been published or currently in press in the course of the Ph.D candidature and are herein appendixed, while the Early Permian brachiopod faunas are systematically described in this thesis. The described Early Permian brachiopod faunas include 127 species, of which 29 are new and 12 indeterminate, and six new genera (subgenera) are proposed; Tarimella, Bmntonella, Marginifera (Arenaria), Marginifera (Nesiotia), Baliqliqia and Ustritskia. A new integrated brachiopod biostratigraphical zonation scheme is proposed, for the first time, for the latest Devonian-Early Permian sequences of the entire Tarim Basin on the basis of this study as well as previously published information (including the Candidate's own published papers). The scheme consists of twenty three brachiopod acm biozones, most of which replace previously proposed assemblage or assemblage zones. The age and distribution of these brachiopod zones within the Tarim Basin and their relationships with other important fossil groups are discussed. In terms of regional correlations and biostratigraphical affinities, the Late Devonian to Early Carboniferous brachiopod faunas of the Tarim Basin are closest to those from South China, while the Late Carboniferous faunas demonstrate strong similarities to coeval faunas from the Urals, central Asia, North China and South China. During the Asselian-Sakmarian, strong faunal links between the Tarim Basin and those of the Urals persisted, while at the same time links with central Asia, North China and South China weakened. On the other hand, during the Artinskian-Kungurian times, affinities of the Tarim faunas with the Urals/Russian Platform rapidly reduced, when those with peri-Gondwana (South Thailand, northern Tibet) and South China increased. Thirty lithofacies (or microfacies) types of four facies associations are recognised for the Late Devonian to early Permian sediments. Based on detailed lithostratigraphy, biostratigraphy and facies analysis, 23 third-order sequences belonging to four supcrsequences are identified for the Late Devonian to Early Permian successions, from which sea-level fluctuation curves are reconstructed. The sequence stratigraphical analysis reveals that four major regional regressions, each marking a distinct supersequence boundary, can be recognised; they correspond to the end-Serpukhovian, end-Moscovian, late Artinskian and end-Kungurian times, respectively. The development of these sequences is considered to have been formed and regulated by the interplay of both eustasy and tectonism. Using the system tract of a sequence as the mapping time unit, a succession of 47 palaeogeographical maps have been reconstructed through the Late Devonian to Early Permian. These maps reveal that the Tarim Basin was first immersed by southwest-directed (Recent geographical orientation) transgression in the late Famennian after the Caledonian Orogeny. Since then, the basin had maintained its geometry as a large, southwest-mouthed embayment until the late Moscovian when most areas were the uplifted above sea-level. The basin was flooded again in late Asselian-Artinskian times when a new transgression came from a large epicontinental sea lying to its northwest. Thereafter, marine deposition was restricted to local areas (southwestern and northwestern margins until the late Kungurian, while deposition of continental deposits prevailed and continued through the Middle and late Permian into the Triassic.