![]() ![]() This vegetation type matches the general composition of the Late Permian Subangara flora, recognized on the basis of plant megafossil records from Eurasia ( 24). The form-genera Scutasporites and Lueckisporites represent subordinate conifers. The presence of a variety of pteridosperm taxa (particularly Peltaspermales) is evident from Vittatina, Weylandites, Striatoabieites, Protohaploxypinus, Lunatisporites, as well as the majority of alete bisaccoid pollen. The abundance of Inaperturopollenites suggests a dominance of cordaites. The pollen record of the upper part of the Schuchert Dal Formation reflects widespread, dense gymnosperm woodland. Information on the botanical affinity of the categories is summarized in Table 1. Palynological AnalysisĪ percentage diagram for selected spore and pollen categories from the P-Tr transition in Jameson Land is presented in Fig. The carbon-isotope profile for carbonates displays relatively high δ 13C values in the Schuchert Dal Formation that are followed by a significant decline in the basal part of the Wordie Creek Formation ( 11). In addition, there are monospecific blooms of the foraminifera Earlandia, similar to age-equivalent occurrences in other parts of the world ( 13). It is uncertain whether these are juveniles or dwarfed adults, but both possibilities may indicate stressed environmental conditions. ![]() Some beds contain large amounts of very small (<1 mm) bivalves and gastropods. Despite the absence of macrofossils, the “dead zone” is by no means devoid of fauna. 12 International Union of Geological Sciences, ). At this level, the fauna also contains the first unquestionable specimens of Hindeodus parvus, the conodont element that has been accepted recently to formally define the base of the Triassic at Meishan, China (ref. After an 8-m sampling gap because of a lack of outcrop, a more diverse record starts at 23.5 m above the base of the Wordie Creek Formation. Despite some possible Permian records ( 12), Claraia generally is regarded as an Early Triassic marker. After a “dead zone,” macrofossils reappear 14 m above the base of the Wordie Creek Formation, when the bivalve Claraia appears and begins to dominate the low-diversity benthic macrofauna. In southern Jameson Land, distinctive Permian-type invertebrate macrofossils, including ammonoids ( Paramexicoceras), solitary rugose corals, and brachiopods such as Martinia, disappear within the upper 5 m of the Schuchert Dal Formation ( 11). On the basis of palynological data from a “dead zone” in a Permian–Triassic (P-Tr) transition sequence from East Greenland, in this paper we document evidence of nonequilibrium vegetation dynamics resulting in selective but time-delayed extinctions among woody gymnosperms. In contrast to faunal records, therefore, successive pollen and spore assemblages from marine “dead zones” may provide the sample size needed to detect population and community responses to global ecological crisis. ![]() Despite bias introduced by over- or underrepresentation, assemblages of dispersed pollen and spores broadly reflect the regional composition of terrestrial plant communities ( 8). These can be transported readily by wind and water to a wide variety of terrestrial and marine depositional settings. Annually, land plants release huge amounts of pollen and spores. Another feature of vegetation is its unique fossilization potential. Refugia with suitable habitats for survival of plant taxa can develop only from progressive range fragmentation and range contraction of populations. As a result of their immobility and restricted rate of dispersal, disappearance of plant taxa cannot be related to rapid emigration in the face of environmental disturbance. ![]() Land plants possess a number of features that yield both challenges and opportunities for the development of new insights into extinction dynamics at the time of “dead zone” formation. ![]()
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