Permian Stratigraphy Research Articles

A new species of Lepidopteris discovered from the Upper Permian of China with its stratigraphic and biologic implications

A new species Lepidopteris baodensis sp. nov. belonging to the family Peltaspermaceae and represented by two ultimate pinnae in the collection under study, was recently discovered at the Baijiagou of Baode, Shanxi, China, from the Upper Permian Sunjiagou Formation. The lower surface of the ultimate rachis, the midrib and secondary veins is covered with triangular, trapezoid, rounded, or ligulate subepidermal swellings, which show different natures from intercalary pinnules. Lepidopteris is one of typical elements of the Late Permian Euramerican flora. Since Schimper erected the genus Lepidopteris in 1869, the entire epidermal structure of subepidermal swellings had been unclear. The new species L. baodensis clearly showing the distinguished epidermal structure of subepidermal swellings, not only enlarges and supplements our knowledge in biology and taxonomy of Lepidopteris as well as the Upper Permian stratigraphy of China, but also provides an opportunity to understand the relationship between Euramerican floras and Cathaysian floras in paleoclimatic, paleoenvironmental and paleogeographic context.

The appearance of an oxygen-depleted condition on the Capitanian disphotic slope/basin in South China: Middle–Upper Permian stratigraphy at Chaotian in northern Sichuan

The global environmental changes related to the end-Guadalupian (Permian) extinction have been recently studied in various shallow-marine sections in the world; however, no previous stratigraphic research focused on the sequence deposited in a relatively deep disphotic zone. In order to investigate the environmental changes in the disphotic zone during that interval, lithostratigraphy and secular changes in the sedimentary environment were analyzed for the ca. 150m thick Guadalupian–Lopingian (Middle–Upper Permian) carbonates at Chaotian in northern Sichuan, South China. The upper Guadalupian Maokou Formation and the Lower Lopingian Wujiaping Formation are mostly composed of bioclastic limestone of a euphotic shelf facies and contain abundant shallow marine fossils, such as algae, corals, and fusulines. The topmost Maokou Formation (ca. 11m thick) is unique in this section because it is composed of thinly bedded black mudstone/chert of a disphotic slope/basin facies with abundant radiolarians and ammonoids. The stratigraphic changes in litho- and bio-facies suggest a two-stepped transgression in the Capitanian followed by a great regression around the Guadalupian–Lopingian boundary (G–LB). Moreover, the stratigraphic changes in bioturbation, total organic carbon (TOC) content, and occurrence of framboidal pyrite suggest that the redox of the sedimentary environment at Chaotian changed drastically in accordance with newly clarified rapid sea-level fluctuations. In association with the Capitanian sea-level rise, the sedimentary environment shifted from an oxic shelf to an oxygen-depleted slope/basin, and again returned to an oxic shelf during the following great regression. The appearance of the oxygen-depleted condition on the Capitanian disphotic slope/basin in northern Sichuan is particularly important because it occurred clearly before the end-Guadalupian extinction event. It is also noteworthy that the oxygen-depleted seawater appeared for the first time on a continental margin significantly before the well-known P–TB shallow-marine anoxia.

Stratigraphy of Upper Permian and Lower Triassic Strata of the Žiri Area (Slovenia)

The paper deals with the stratigraphy of Late Permian and Early Triassic strata of the Lukač section in the Žiri area of western Slovenia. This is the only section presently known in the External Dinarides where the Permian- Triassic boundary is defined following international criteria based on the first appearance of the conodont Hindeodus parvus. The following lithostratigraphic units have been formalized: the Bellerophon Limestone and Evaporite-dolomite Members of the Bellerophon Formation and the Lukač Formation with the three members, the Transitional Beds, Streaky Limestone and Carbonate-clastic Member. The paper presents the results of micropaleontological study based on foraminifers and conodonts as well as petrographic and sedimentologic research results. The investigation of conodont assemblages enabled the conodont biozonation of the Permian-Triassic interval of the studied Lukač section.

A Huge Caseid Pelycosaur from North-Western Sardinia and Its Bearing on European Permian Stratigraphy and Palaeobiogeography

Skeletal remains, some loose on the surface and others still embedded, have been recovered from the uppermost part of an outcrop of the Permian Cala del Vino Formation located near Torre del Porticciolo (Alghero, Nurra, NW Sardinia). Taphonomic analysis suggests that all the elements pertain to a single individual; ongoing studies indicate the fossil represents a large caseid close (or referable) to Cotylorhynchus; otherwise restricted to a narrow geographic and stratigraphic zone of the central USA. The new finding, the first of a caseid in Italy and one of few in Europe, enlarges the known distribution of the family and provides a significant and key chronostratigraphic constraint for the continental succession of this area and, in turn, helps establish a stratigraphic framework for the Permian units cropping out in Italy and southern France.

Progress, Problems and Prospects on the Stratigraphy and Correlation of the Kungurian Stage, Early Permian (Cisuralian) Series

Abstract:The Kungurian Stage is one of the three remaining stages of the Permian that is not yet defined at the base by a Global Stratotype Section and Point (GSSP). The candidate section at the Yuryuzan' River in the Urals yields few conodonts, and contains non‐marine sediments near the boundary. The search for a suitable, continuous marine succession is a principal task for the Subcommission on Permian Stratigraphy. The Leonardian, with its type area in the southwest United States, and in objective stratigraphic succession directly beneath the basal Guadalupian Roadian Stage, has priority to serve as a subseries of the Lower Permian. However, distinct provincialism limits the correlation of Leonardian fossil zones with the fusuline‐based Tethyan timescale. Conodonts can be correlated in many important regions on opposite sides of Pangea, yet contradictions arise when relating conodont zones with fusuline and ammonoid zones. The different taxonomic philosophies are highly suspected for the cause of the conflicts, but also there are different conodonts from the type Roadian in West Texas. Given that the Pamir and Darvaz in central Asia are difficult to access, further investigations should focus on South China, where abundant fusulines and ammonoids facilitate correlation throughout the Tethyan region, and where conodonts permit correlation with North America.

The Permian–Triassic boundary in Western Australia: evidence from the Bonaparte and Northern Perth basins—exploration implications

Several sedimentary basins in Western Australia contain petroleum reservoirs of Late Permian or older age that are overlain by thick shaly sequences (400–2,000 m) that have been assigned an Early Triassic age. The age of the base of the Triassic shales has been, and continues to be, contentious with strata being variously ascribed to the latest Permian (Changhsingian Stage) or wholly in the earliest Triassic (Induan Stage). In the Perth Basin the Permian-Triassic boundary appears to be located somewhere in the Hovea Member of the Kockatea Shale. In the Bonaparte Basin, the boundary would appear to be either in the uppermost Penguin Formation or at the boundary between the Penguin and Mairmull formations. The uncertainty of the boundary placement relates to the interpretation of the sedimentological, biostratigraphic and geochemical record in individual sections and basins. Major problems relate to the recognition, or even the presence of unconformities, complications related to the presence of reworked sediments and paleontological material (both conodonts and spore-pollen) and to the significance of geochemical shifts. The age of the basal Kockatea Shale (northern Perth Basin) and the basal Mt Goodwin Sub-group (Bonaparte Basin) is reassessed using palaeontological data, augmented by carbon isotopic measurements and geochemical analyses, supported by wireline log correlations and seismic profiles. The stratigraphy of the latest Permian to Early Triassic succession in the Bonaparte Basin is also revised, as is the nomenclature for the Early Triassic Arranoo Member of the Kockatea Shale in the northern Perth Basin. The Mt Goodwin Sub-group (new rank) is composed of the latest Permian Penguin Formation overlain by the Early Triassic Mairmull, Ascalon and Fishburn formations (all new).

Carboniferous to Lower Permian stratigraphy of the southern Tamworth Belt, southern New England Orogen, Australia: Boundary sequences of the Werrie and Rouchel blocks*

Carboniferous to Lower Permian successions along the western border of the Tamworth Belt between Wallabadah and Muswellbrook were remapped to clarify the stratigraphy and establish a boundary between the Werrie and Rouchel blocks. The boundary, located at the Waverley Fault, separates Carboniferous sequences containing different formations and volcanic members. SHRIMP AS3 dating of volcanic members indicates that successions within the Rouchel and Gresford blocks were deposited, uplifted and eroded at different times. The lacustrine Woodton Formation in the Werrie block, previously considered Carboniferous, is earliest Permian (Asselian) from palaeobotanical and SHRIMP AS3 evidence. Stratigraphic and palaeoenvironmental differences between the Werrie and Rouchel blocks suggest that they were not directly juxtaposed during the greater part of the Carboniferous, supporting palaeomagnetic evidence that blocks within the Tamworth Belt are allochthonous. Superposition of the western extremity of the Waverley Fault by Lower Permian (Sakmarian) formations and intrusion of folded and faulted Devonian to Lower Permian successions by the Barrington Tops Granodiorite (ca 280 Ma) indicate that the Werrie, Rouchel and Gresford blocks were subjected to tectonism before the Late Permian Hunter – Bowen Orogeny.

An overview of Permian marine stratigraphy and biostratigraphy of Mongolia

This paper summarizes the spatial distribution, stratigraphical divisions and biostratigraphical zonation schemes of Permian marine deposits in Mongolia. Where appropriate, correlations of the various Permian marine biostratigraphical units with those of adjacent regions are also reviewed and discussed. In general, Permian marine sequences are developed in two separate basins: one in central and northeastern Mongolia where the Permian stratigraphy and marine faunas bear strong similarities with those of the Transbaikal, Verkhoyansk and Kolyma–Omolon regions of southern and eastern Russia; and the other in southeastern Mongolia where the Permian marine faunas and rock sequences are closest to those of northeast China and southern Primorye of Far East Russia.

South Primorye, Far East Russia—A key region for global Permian correlation

Significant differences between faunal and floral associations existing in different paleogeographic realms in the Kungurian–Late Permian interval make it difficult to correlate the Permian deposits of the world. Resolving this problem is one of the main tasks of Permian stratigraphy. The global significance of Permian strata of the Primorye region of Far East Russia is enhanced by the specific Middle Permian mixed Tethyan, Boreal and Gondwanan-type brachiopod fauna, mixed Angara-Euromerican-Cathaysian flora, and their close spatial and stratigraphical association with fusulinids, bryozoans, ammonoids, conodonts. These facts permit tracing of global correlational levels of some Permian sequences within the different paleobiogeographical realms: for example, the Monodiexodina sutschanica- Metadoliolina dutkevichi fusulinid zone of the Wordian age and Parafusulina stricta fusulinid zone of the Capitanian age. The Late Permian fauna of the Primorye is mainly Tethyan in origin and provides correlation with similar aged sequences from South China.

Permian stratigraphy and correlation of Northeast China: A review

Palaeontological, lithostratigraphical data from the Permian strata and correlation of the Permian successions for different tectonic units in Northeast China are reviewed and summarized in this paper. Permian strata in Northeast China are dominated by brachiopods, fusulinoideans and land plants, with limited ammonoids, conodonts and bivalves. The Cisuralian (Early Permian) in the northern margin of the North China Block and in the Manchuride Belt is composed mostly of marine massive limestone with the characteristic Pseudoschwagerina Zone in the Asselian and Sakmarian and the Misellina claudiae Zone in the Kungurian. The Cisuralian in the Xing'an Block and the northeastern part of Inner Mongolia is dominated by huge terrestrial deposits with fossil plants. The Guadalupian (Middle Permian) in the Manchuride, Altaid and Yanbian Belts are characterized by bi-temperate Roadian or early Wordian Monodiexodina fauna and the late Wordian–Capitanian Codonofusiella– Schwagerina or Neoschwagerina– Yabeina faunas, the mixed brachiopod faunas between the Boreal/antitropical and the Palaeoequatorial Cathaysian forms, the Roadian or early Wordian solitary coral faunas, and the late Wordian–Capitanian compound Waagenophyllum– Wentzelella fauna. The Nadanhada Terrane contains some exotic limestone blocks with a typical Cathaysian Neoschwagerina– Yabeina fauna in a Late Jurassic–Early Cretaceous mélange, which is related to Mesozoic subduction in the western Circum-Pacific region. The Lopingian (Late Permian) in Northeast China is mostly characterized by terrestrial molasse deposits with a mixed flora between the Boreal Angaran and the palaeoequatorial Cathaysian Provinces, indicating the final closure of the Palaeo-Asian Ocean.

Sequence stratigraphy and correlation of late Carboniferous and Permian in the CIS, Europe, Tethyan area, North Africa, Arabia, China, Gondwanaland and the USA

Sequence stratigraphy was used to correlate the depositional chronology during Permo–Carboniferous time in various sedimentary basins of Gondwanaland, western Europe, eastern Europe, Tethyan area, North Africa, Arabia, China, and North America. During late Carboniferous and Permian, eleven second-order sequences (SOS) were recognised throughout the whole area. The sequence SI is Serpukhovian pp, Namurian A pp and Chesterian. The sequence SII is Serpukhovian pp–Bashkirian pp, Namurian A pp-B-C–Westphalian A–B pp and Morrowan. The sequence SIII is late Bashkirian–Moscovian, Westphalian B pp-C-D and Atokan–Desmoinesian. The sequence SIV is Kasimovian, early Stephanian and Missourian. The sequence SV is Gzhelian–Orenburgian, late Stephanian and Virgilian. The sequence SVI is Asselian, Autunian and Nealian. The sequences SVII–IX are Saxonian, Sakmarian–Artinskian–Kungurian and Leonardian–Hessian–Cathedralian. The sequences SX–XI are Guadalupian and Lopingian. Depending on the regional setting, different relationships exist between marine transgression and the respective effects of tectonics and of sea-level changes: in western Europe, effects of the glacial processes in Gondwanaland are partly balanced by the late compression in the Hercynian belt during Moscovian. Eastern Europe, Tethyan area, North Africa, China, and North America show a good correlation between glacial (ice melting) processes in Gondwanaland and the intensity of the transgression which is increased by the westward progradation of the orogeny in Urals and Appalachians. In Arabia, Tunisia and Tethyan area, the impact of the Neotethys opening is obvious from the Artinskian and mainly during the late Permian.

Mesozoic break-up of SW Gondwana: implications for regional hydrocarbon potential of the southern South Atlantic

This work provides new palinspastic palaeofacies reconstructions of SW Gondwana incorporating rotation of a Falkland/Malvinas microplate. We discuss the implications of this for the tectonic evolution of the southern South Atlantic and hence for the regional hydrocarbon potential. Existing Gondwana reconstructions display good fits of major continents but poorly constrained fits of microcontinents. In most continental reconstructions, the Falkland/Malvinas Plateau was assumed to be a rigid fragment of pre-Permian South American crust. However, it has been suggested, on the basis of palaeomagnetic data, that the Falkland/Malvinas Islands were rotated by ∼180° after 190 Ma. This rotation hypothesis has been successfully tested on the basis of Devonian stratigraphy and palaeontology, Permian stratigraphy and sedimentology and Late Palaeozoic and Early Mesozoic structure, making it unlikely that the plateau behaved as a rigid structure during breakup. We have explored the consequences of accepting this hypothesis for the tectonic evolution of SW Gondwana by compiling new palaeogeographic maps for the Permian–Cretaceous of the southern Atlantic area. To achieve a realistic close fit, we have devised a pre-rift proxy for the ocean–continent boundary for the South Atlantic. In order to produce the best fit, it is necessary to subdivide South America into four plates. The consequences of this are far-reaching. Our work suggests that although sedimentary basins were initiated at different times, three major tectonic phases can be recognised; in regional terms these can be thought of as pre-, syn- and post-rift. During the pre-rift time (until the Late Triassic), the area was dominated by compressional tectonism and formed part of the Gondwana foreland. The Falkland/Malvinas Islands lay east of Africa, the Falkland/Malvinas Plateau was ∼33% shorter and Patagonia was displaced east with respect to the rest of South America, in part along the line of the Gastre Fault System. Potential source facies are dominantly post-glacial black shales of Late Permian age deposited in lacustrine or hyposaline marine environments; these rocks would also be an effective regional seal. Sandstones deposited in the Late Permian would be dominantly volcaniclastic with poor reservoir qualities; Triassic sandstones tend to be more mature. There was significant extension from about 210 Ma (end-Triassic) until the South Atlantic opened at about 130 Ma (Early Cretaceous). In the early syn-rift phase, extension was accompanied by strike-slip faulting and block rotation; later extension was accompanied by extrusion of large volumes of lava. Early opening of the South Atlantic was oblique, which created basins at high angle to the trend of the ocean on the Argentine margin, and resulted in microplate rotation in NE Brazil. Intermittent physical barriers controlled deposition of Upper Jurassic–Cretaceous anoxic sediments during breakup; some of these mudrock units are effective seals with likely regional extent. During crustal reorganisation, clastic sediments changed from a uniform volcaniclastic provenance to local derivation, with variable reservoir quality. In the late rift and early post-rift phase, continental extension changed from oblique to normal and basins developed parallel to the continental margins of the South Atlantic. This change coincides with the main rifting in the Equatorial basins of Brazil and the early impact of the Santa Helena Plume. It resulted in widespread development of unconformities, the abandonment of the Recôncavo–Tucano–Jatoba rift and the end of NE Brazil plate rotation, which remained attached to South America. There was extensive deposition of evaporites, concentrated in (but not restricted to) the area north of the Rio Grande Rise/Walvis Ridge. Widespread deposits can be used to define potential regional elements of hydrocarbon systems and to provide a framework for relating more local elements. Our main conclusion is that the regional hydrocarbon potential of the southern South Atlantic has been constrained by the tectonic evolution.

Permian sedimentary record of the Turpan-Hami basin and adjacent regions, northwest China: Constraints on postamalgamation tectonic evolution

The Permian marks an important, yet poorly understood, tectonic transition in the Tian Shan region of northwestern China between Devonian–Carboniferous continental amalgamation and recurrent Mesozoic–Cenozoic intracontinental orogenic reactivation. The Turpan-Hami basin accommodated up to 3000 m of sediment and is ideally positioned to provide constraints on this transition. New stratigraphic data and mapping indicate that extension dominated Early Permian tectonics in the region, whereas flexural, foreland subsidence controlled Late Permian basin evolution. Lower Permian strata in the northwestern Turpan-Hami basin consist of coarse- grained debris-flow and alluvial-fan deposits interbedded with mafic to intermediate volcanic sills and flows. In contrast, Lower Permian rocks in the north-central and northeastern Turpan-Hami basin unconformably overlie a Late Carboniferous volcanic arc sequence. These Lower Permian strata include possible shallow-marine carbonate rocks and thick volcanic and volcaniclastic rocks that are in turn overlain by littoral- to profundal-lacustrine facies. Above a regional Lower Permian/Upper Permian unconformity, regional sedimentation patterns record the development of a more integrated sedimentary basin. The Upper Permian is entirely nonmarine and can be correlated east-west along the depositional strike of the basin. The lower Upper Permian consists of a broad belt of braided fluvial deposits shed northward. These strata are overlain by fluctuating littoral- and profundal-lacustrine facies and associated fluvial facies. The uppermost Permian is characterized by shallow lake- plain and fluvial environments. The Early Permian association of diffuse volcanism and partitioning of subbasins by normal faulting is consistent with an early phase of lithospheric extension. Local relationships indicate west-east extension in the Turpan-Hami basin along faults oriented normal to Late Devonian–Carboniferous collisional sutures within the Tian Shan. The cause of extension in the wake of Carboniferous orogenesis remains enigmatic. However, the temporal and spatial relationships of the two strain regimes suggest that they are genetically related. Upper Permian stratigraphy and unconformities and local Late Permian–Triassic contractional deformation record foreland-basin development when the Turpan-Hami region became a wedge-top basin with respect to the north Tian Shan fold-and-thrust belt. Flexurally induced Late Permian subsidence is also manifested in the larger Junggar basin to the north, where >4000 m of strata are preserved in the foredeep region. The Turpan- Hami and Junggar basins were depositionally connected for much of the Late Permian when a vast lacustrine system developed across northwestern China. This lacustrine paleogeography was only occasionally interrupted, possibly by structural damming during uplift of the orogenic wedge.

Permian of West Yunnan, Southwest China: a biostratigraphic synthesis

Recent progress in the study of Permian stratigraphy of western Yunnan, southwest China, is reviewed with particular references to the Tengchong and Baoshan blocks and the Changning–Menglian Belt. Where confusion or controversy exists in stratigraphical nomenclature and/or dating, we attempt to clarify the situation based on our recent field observations and newly obtained research results. The Permian within the Changning–Menglian Belt embraces different stratigraphic successions, suggesting different tectonic settings, ranging from passive margin and active margin, to oceanic basin and seamounts. Permo-Carboniferous faunas in the carbonate sequences of the Changning–Menglian Belt are of typical Cathaysian affinity, as demonstrated by abundant fusulinaceans and compound rugose corals. The Permian stratigraphy and faunas of the Tenchong and Baoshan blocks are markedly different from those of the Changning–Menglian Belt. The Baoshan Block lacks Upper Carboniferous deposits, and its subsequent Lower Permian sequence consists predominantly of siliciclastic strata yielding cool-water faunas and possibly glaciogene diamictites, overlain by thick basaltic lava and volcaniclastics of probably rift origin. The upper part of the Permian in the Baoshan Block is characterized by carbonates containing mixed Cathaysian and Gondwanan faunas. The Tengchong Block has a similar evolutionary history to the Baoshan Block, but completely lacks volcanic rocks.

Cenozoic tectonics and landform evolution of the coast and adjacent highlands of southeast New South Wales

This paper has been written firstly to dispel a widely held notion that the structure and stratigraphy of Permian and Triassic sedimentary rocks of the southern Sydney Basin precludes post‐Permian tectonic lowering of the coastal zone of southeast New South Wales with respect to the highlands; and secondly to present evidence of Cenozoic tectonic lowering of the coastal zone by gentle tilting and, locally, by faulting. The apparent horizontal attitude of Triassic sandstone in an east‐west section inland from Nowra precludes later faulting or steep monoclinal folding in this immediate area, but does not preclude geomorphically significant tilting or gentle warping; and it places no constraints on the tectonic and geomorphic history in areas south of the sandstone outcrop. The form of an Oligocene erosion surface around Ulladulla, and the distribution of older rock units below this surface are also not incompatible with significant Cenozoic tectonism. Near Ulladulla, Mogo, Moruya, and Merimbula, mid‐Cenozoic non‐marine sediments and basalts in north‐south‐trending palaeovalleys dip gently seaward at angles around 1°—about the same as the eastward slope of the offshore seismic basement and also similar to the average slope between the coastal zone and inland plateaux; indicating that the coastal zone and continental shelf have been downwarped relative to the inland plateaux in these areas. The area between Brooman, on the Clyde River, and the coast between Termeil and Batemaʼns Bay, has been lowered by Cenozoic faulting. The steep slope on the west side of the Clyde River is a dissected 200–300 m fault scarp, and there are two other east‐facing fault scarps between the Clyde River and the coast. Fault blocks between the Clyde River and the coast are gently backtilted to the west. Further south, there may be more faults and tilt blocks between Batemaʼns Bay and Moruya. Tectonic lowering of the coastal zone and continental shelf appears to be mostly post‐mid‐Cenozoic. This suggests that marine shelf sediments are likely to be not older than Miocene. There could also be older Cenozoic non‐marine sediments and perhaps basalts in palaeovalleys at the base of the section.

PERMIAN FUSULINID ASSEMBLAGES AND STRATIGRAPHY OF THE TRANSCAUCASIA

The Permian sequence of the Transcaucasia, which comprises the Davaly, Asni, Gnishik, Arpa, Khachik, and Akhura Formations, is described. A precise dating of the formations based on the analysis of fusulinid assemblages is also provided. The Davaly Formation corresponds to the Bolorian Stage of the Lower Permian (Cisuralian); the Asni Formation corresponds to the Kubergandian Stage, and to the lower half of the Murgabian Stage of the Middle Permian (Guadalupian); the Gnishik Formation corresponds approximately to the upper half of the Murgabian Stage; and the Arpa and Khachik Formations represent the entire Midian Stage of the Middle Permian. Only the uppermost Chanakhchy Beds of the Khachik Formation are referred to the upper series of the Permian (Lopingian), based on the latest proposal of the International Subcommission on Permian Stratigraphy concerning series boundaries. The Akhura Formation encompasses the Dzhulfian and Dorashamian Stages of the Upper Permian. Refined correlations between the Permian sequence of the Transcaucasia and the most complete Permian sequences of the Tethyan region (Central Iran, southestern Pamirs, South China, Japan ) are presented. The transgressive overlapping of the Permian deposits is recorded in these areas, similar to the Transcaucasia. Although the transgression began during the Bolorian, it reached the widest extent in the Kubergandian and therefore, in most sections the transgressive series begins with deposits of Kubergandian age. The Middle and Upper Permian deposits of the Transcaucasia, Iran, and southern Turkey belonged to a single carbonate platform. Similar extensive carbonate platforms are recorded in the southern parts of Afghanistan and China. A change in the sedimentary regime was recorded in all these platforms at the boundary between the Guadalupian and Lopingian epochs. The Guadalupian time was marked by the intensive accumulation of biolitithic and detrital limestones produced by benthic organisms, mainly algae and foraminifers, whereas in the Lopingian time, carbonate and clayey micritic deposition dominated, and the role of nectonic-planctonic and nectonic organisms, such as cephalopods and conodonts, increased. The sedimentation change was abrupt and caused probably by the short-term post-Midian regression. The change resulted in a significant biotic crisis when larger fusulinids, goniatitids and agoniatitids, tabulate corals, most rugose corals and other organisms became entirely extinct. These events marked the onset of the Late Permian Great Extinction, which ended at the Permian/Triassic boundary. Nine paleontological plates show the main fusulinid assemblages. Nine new species are described: Codonofusiella (?) vediensis , Chalaroschwagerina davalensis , Pseudofusulina arpaensis , P. araxensis , P. pjatakovae , Rugosochusenella davalensis , Misellina ( Misellina ) caucasica , Cancellina armenica , and Sumatrina vediensis .

40Ar/39Ar Dating of Langbeinite [K2Mg2(SO4)3] in Late Permian Evaporites of the Salado Formation, Southeastern New Mexico, USA

Late Permian stratigraphy of the southwestem United States reveals an overall shoaling trend between the Guadelupian Stage and the end of the Permian. The shoaling sequence features an upsection progression between marine carbonates, evaporates, and terrestrial red-beds. The virtual absence of fauna in the evaporates and red-beds, which define the Ochoan Series, precludes biostratigraphic age assignment. Thus the duration of the shoaling sequence, and correlation with the global Late Permian record of events is problematic. 4~ (sanidine) dates for tufts in red-beds of the Quartermaster Fm., at the top of the Ochoan Series in west Texas, bracket the 250.0 Ma 4~ age determined for the Permian/Triassic boundary at the Meishan section in south China (Renne et al., 1995). In an effort to extend the geochronological framework downsection, we have undertaken 4~ analysis of K-rich evaporate minerals from the Salado Formation. The Salado Formation comprises c. 600-700 m of hypersaline evaporites whose top lies c. 100 m below the Quartermaster Fm. through much of west Texas and southeastern New Mexico (e.g. Lowenstein, 1988). Nine horizons of K-rich bittern salts occurring in the McNutt Potash Zone of the Salado Fm. are mined for potash, and commonly contain the mineral langbeinite whose composition is K2M92(S04)3. Langbeinite in other occurrences has been dated by K-Ar (e.g. Pilot and Blank, 1967) and 4~ methods (Lippolt and Oesterle, 1977; Lippolt et al., 1993), and in some cases yielded stratigraphically plausible ages. A sample from the IMC Kalium mine (500 foot level, near the top of the Salado Formation) near Carlsbad N. M. was analysed by incremental heating in a resistance furnace in two experiments. Both samples were about 3 mg single crystals of transparent, highly lustrous langbeinite wrapped in Cu foil. Temperature steps ranged from 450 to 1300~ and were of 600 s and 1800 s duration in the first (IMC-I.1) and second (IMC-1.2) experiments, respectively. Gas release was relatively sluggish up to near the melting temperature, at c. 880~ Based on linear Arrhenius relations (assuming spherical diffusion geometry for this isometric mineral), 39ARK release over the temperature range 600 to 850~ in vacuo appears to occur by volume diffusion, with activation energies of 42.7 _+ 5.7 and 42.6 -t1.9 kcal/mol. These results are indistinguishable from the activation energy of 44 kcal/mol determined by Lippolt and Oesterle (1977) for 4~ diffusion in two different langbeinite samples, and confirm their conclusion that langbeinite is highly argonretentive.

Facies and allostratigraphy of high‐latitude, glacially influenced marine strata of the Early Permian southern Sydney Basin, Australia

The Sydney Basin of New South Wales, Australia is a foreland basin containing a thick (up to 10 km) Permo‐Triassic succession. The southern margin of the basin exposes strata deposited during Late Palaeozoic glaciation of south‐eastern Gondwana. The Early Permian Wasp Head, Pebbley Beach, Snapper Point Formations and Wandrawandian Siltstone were deposited between 277 and 258 Ma on a polar, glacially influenced continental margin adjacent to ice sheets located over East Antarctica and eastern Australia. Sedimentary facies, together with related ichnofacies and fauna, can be grouped into six facies associations that record marine sub‐environments ranging from high energy, storm‐dominated inner shelf to turbidite‐dominated upper slope settings. Cold marine conditions, with near‐freezing bottom water temperatures, are recorded by glendonites. Ice‐rafted debris, most likely deposited by icebergs, occurs in almost all facies associations.An allostratigraphic approach, emphasizing the recognition of bounding discontinuities (i.e. erosion surfaces and marine flooding surfaces), is used to subdivide the Early Permian stratigraphy into facies successions. Three types of succession can be identified and record changes in the relative influence of allocyclic controls such as basin tectonics, sediment supply and glacio‐eustatic sea level variation.Together, sedimentological and allostratigraphic data allow reconstruction of the depositional history of the south‐western margin of the Sydney Basin. Initial marine sedimentation, characterized by sediment gravity flows and storm‐deposited sandstones of the lower Wasp Head Formation, occurred adjacent to a faulted basin margin. Overlying successions within the upper Wasp Head, Pebbley Beach and Snapper Point Formations, record aggradation in inner to outer shelf settings along a storm‐ and glacially influenced continental margin. Tectonic subsidence and basin flooding is recorded by deeper water turbidites of the Wandrawandian Siltstone.

Submarine mass‐wasting deposits as an indicator of the onset of foreland thrust loading—Late Permian Bowen Basin, Queensland, Australia

In the eastern part of the Permo‐Triassic Bowen Basin of Queensland, Australia, a transition from passive, thermal subsidence to flexural (foreland basin) subsidence is recorded within the Upper Permian stratigraphy. Two coarse‐grained intervals containing deposits of mass‐wasting processes occur within an otherwise siltstone‐dominated succession over 1500 m thick (the Moah Creek Beds and equivalents). These intervals can be traced over at least 350 km north–south, along the structural eastern margin of the basin. The lower of the coarse‐grained intervals is spectacularly exposed in the banks of the Fitzroy River, west of Rockhampton. Here, interbedded sandstones and siltstones of marine shelf origin are abruptly truncated by a mudrock succession containing evidence of slumping and contemporaneous magmatic activity. This unit passes up‐section into packages of mass‐flow conglomerates and diamictites, interpreted to have formed on an unstable submarine slope. The character of the mass‐flow deposits, their stratigraphic position and lateral extent are interpreted in terms of destabilization of a sloping marine surface by pulsed, subsurface thrust propagation.

On the carboniferous-permian boundary

An objection has been lodged against the traditional P/C boundary which were still upholded by International Subcommission on Permian Stratigraphy, International Commission on Stratigraphy, IUGS. And the rationality to take the base of theMontiparus Zone as the P/C boundary is comprehensively demonstrated.