查看更多>>摘要：This study presents an integrated conodont succession from the Bozhou section, northern Guizhou Province, southwestern China. These conodonts were yielded from the Changhsingian Changhsing Formation and the Lower Triassic Yelang and Maocaopu Formations, which were deposited in the transitional setting between the clastic shelf and carbonate platform in the western margin of the Yangtze Platform. A total of 22 conodont species of six genera are identified, and 10 conodont zones are recognized from the top part of Changhsing Formation to the Yelang Formation, namely, the Clarkina changxingensis, C. yini, C. meishanensis, Hindeodus praeparvus, H. parvus, H. postparvus, Neoclarkina discreta, Sweetospathodus kummeli, Neospathodus dieneri, and Eurygnathodus costatus Zones in ascending order. Based on the conodont succession, the ages of Shabaowan, Yulongshan, and Jiujitan members of the Yelang Formation are recognized for the first time and assigned to the early Griesbachian, late Griesbachian, and latest Griesbachian to early Smithian. At this section, the Permian-Triassic boundary (PTB) is placed at the base of Bed 7-2, 10 cm below the top of Changhsing Formation, defined by the first occurrence (FO) of H. parvus. The Induan-Olenekian boundary (IOB) is drawn at the base of Bed 49, the uppermost part of Yelang Formation, based on the FO of Eu. costatus immediately overlying the Ns. dieneri Zone in the absence of Novispathodus waageni. The Bozhou conodont successions can be correlated well with other sections worldwide.
查看更多>>摘要：Early flowering plants constituted a minor component of the Early Cretaceous conifer- and fern- dominated flora. However, their pollen provides a rich, albeit incomplete, record of the group's early evolutionary history. Palynological analysis of Barremian-lower Aptian successions from the Biyadh and Shu'aiba formations in the Arabian Gulf reveals remarkably high angiosperm diversity. While Chloranthaceae, magnoliids, monocots, eudicots, and other "basal" groups represent the bulk of flowering plants, pollen with uncertain affinities is also a significant component of the angiosperm assemblage. Analysis of the palaeobiogeographic distribution of angiosperm pollen during the late Barremian-early Aptian allowed us to discern three groups of angiosperms. The first group, including Clavatipollenites, produced pollen with a near-cosmopolitan distribution. The second group, including Stellatopollis, had a somewhat restricted distribution in northern Gondwana and western Laurasia. The pollen distribution of the third group, which includes Dichastopollenites, is restricted to central and/ or northeastern Gondwana. These varied patterns of palaeobiogeographical spread of early angiosperms reflect different migration and colonisation abilities. When compared with coeval palynological successions from other Gondwanan localities, the composition and diversity of the Arabian angiosperm assemblages support early hypotheses on the radiation of angiosperms that identify northeastern Gondwana as one of the most important centres of angiosperm diversification.The following new taxa are described: Splitipollis gen. nov., Splitipollis reticulatus sp. nov., Tucanopollis doylei sp. nov., Pennipollis spinosus sp. nov., Clavamonocolpites woodii sp. nov., and Retimonoporites arabiensis sp. nov.
查看更多>>摘要：Lake Grevelingen is a former branch of the Rhine-Meuse-Scheldt estuary, which was artificially transformed into a salt-water lake by a dam in 1971. This transformation induced profound changes in the biological community of the basin, which have been described as an ecodisaster, with seasonal hypoxia/anoxia occurring in the deepest parts of the lake. Here, we investigate a sediment core sampled in 2012 in the Den Osse Basin (34 m depth) of Lake Grevelingen, recording the last -50 years and including the transition from an estuary to a salt-water lake. Sediment molybdenum (Mo) concentrations were used to refine an existing age model based on 210Pb, giving us an estimated precision of +/- 3 years. The benthic foraminiferal succession reflects the anthropogenic modifications in Lake Grevelingen and allows four successive stages to be distinguished: 1) before 1971, when the system was estuarine; 2) from 1971 to 1978, when the system rapidly changed into an enclosed brackish water lake; 3) from 1978 to 1999, when a seaward sluice was opened during winter and 4) the period from 1999 to 2012, with a year-round opening of the sluice and doubling of water exchanges with the North Sea. The foraminiferal record, showing communities mainly dominated by Elphidium selseyense, also highlights the appearance of the putatively exotic Ammonia confertitesta in the mid-1980s, which thereafter progressively replaced the congeneric autochthonous Ammonia aberdoveyensis. Finally, we hypothesise that the activity of cable bacteria, S-oxidising prokaryotes present in the surface sediments of Den Osse Basin in winter and spring, causes dissolution of foraminiferal tests by decreasing the pore water carbonate saturation state in the sediments directly below the oxic zone. This explains the contrast between the abundant living populations and the very low numbers of foraminiferal shells preserved in the top -15 cm of the sediment.
Wheeler, AlexanderShen, JianMoore, Tim A.Moroeng, Ofentse M....
24页
查看更多>>摘要：In this contribution, we report the palynology, organic petrography and carbon isotopes for the #16 Seam in the Lower Cretaceous Yimin Formation of the Hailar Basin, Inner Mongolia, China. Eighteen palynological samples were collected from the coal seam as well as from intraseam partings and the immediate roof. Microfloras comprise a diverse assemblage of ferns, conifers, horsetails, lycopsids, bryophytes, ginkgoes and cycads. Conifer pollen is common, especially representative of Pinaceae (Pinuspollenites) as well as Cheirolepidiaceae (Classopollis) and Araucariaceae (Araucariacites, Chasmatosporites); however, this material is interpreted as mostly derived from an upland source rather than from the mire-forming vegetation. An overrepresentation of conifer pollen may explain the relatively poor abundance and diversity of ginkgo and cycad pollen, compared to what is found in the macrofossil record. The palynological assemblage found in Seam #16 indicates a Barremian to Aptian age. Maceral composition, ash yields, and 613Corg signature of the coal suggest peat accumulation was controlled by a rising water table from flooding of the mire, coupled with significant ground (peat) fires and/or surface wildfires. These conditions resulted in high levels of detrital mineral matter and charcoal input, the latter represented by inertodetrinite in the coals. The top of the coal seam is characterised by a higher ash yield, lower 613Corg values and increased sphagnacean spores, which suggest the gradual drowning of the palaeomire. Although angiosperms were present in the Hailar Basin during the time that Seam #16 was accumulating, they are absent from the pollen found in this study. This may indicate that they were not yet adapted to the extreme conditions of the mire (e.g., acidity, anoxia), and unable to compete with the established mire vegetation.
Deza-Araujo, MaraMorales-Molino, CesarConedera, MarcoHenne, Paul D....
14页
查看更多>>摘要：The reconstruction of human impact is pivotal in palaeoecological studies, as humans are among the most important drivers of Holocene vegetation and ecosystem change. Nevertheless, separating the anthropogenic footprint on vegetation dynamics from the impact of climate and other environmental factors (disturbances such as fire, erosion, floods, landslides, avalanches, volcanic eruptions) is a challenging and still largely open issue. For this purpose, palynologists mostly rely on cultural indicator pollen types and related indices that consist of sums or ratios of these pollen types. However, the high environmental and biogeographical specificity of cultural indicator plants hinders the application of the currently available indices to wide geographical settings. Furthermore, the achievable taxonomic resolution of cultural indicator pollen types may hamper their indicative capacity. In this study, we propose the agricultural land use probability (LUP) index, a novel approach to quantify human impact intensity on European ecosystems based on cultural indicator pollen types. From the 'classic' cultural indicators, we construct the LUP index by selecting those with the best indicator capacity based on bioindication criteria. We first train the LUP index using twenty palynological sequences along a broad environmental gradient, spanning from treeless alpine to subtropical mediterranean evergreen plant communities. We then validate the LUP index using independent pollen datasets and archaeological proxies. Finally, we discuss the suitability of the selected pollen types and the potential of the LUP index for quantifying Holocene human impact in Europe, concluding that careful application of the LUP index may significantly contribute to refining pollen-based land-use reconstructions.
NSTL
Elsevier