The influence of sequence stratigraphic (sea-level driven) processes on patterns derived from the fossil record is receiving increasing attention. This study explores stratigraphic anatomy of diversity patterns across two late Quaternary 4th order sequences deposited on the Po Plain (Italy) over the last 150 k.y. (i.e., the two most recent glacial-interglacial cycles). The rich mollusk fauna, dominated by extant forms, preserved as a part of well-understood eustatic cycles, offers a testing ground for exploring how climate-driven sea level changes influence sample diversity, diversity turnover, and higher-order diversity patterns within and across systems tracts and sequences. These two 4th-order depositional sequences were densely sampled from three cores. The data (150 species and 22776 specimens from 29 Holocene and 19 Pleistocene samples) were analyzed using single-sample and multi-sample rarefaction techniques. In all three cores and for both cycles, sample-level diversity decreased upward within sequences: the late Transgressive Systems Tract (TST) samples displayed the highest equitability and richness and the Highstand Systems Tract (HST) samples displayed the lowest diversity (the trend primarily reflects the increase in the dominance of most common species in HST samples). This pattern is likely due to a combination of ecological, environmental, and taphonomic processes. Multi-sample rarefaction indicates that species turnover is more limited in transgressive phases of both depositional cycles. This trend may reflect increasing environmental heterogeneity of marginal habitats averaged within shallowing-upward successions and/or decreasing time averaging associated with increasing sedimentation rates during HST phases of the cycles. The sequence and multi-sequence diversity levels are lower than those observed within individual late-TST systems tracts, indicating that species turnover was minimal both within as well as across the last two glacial-interglacial cycles. The study shows that species richness and equitability patterns of the most common mollusk species track closely the sequence stratigraphic architecture of late Quaternary successions of Po Plain.
Sequence stratigraphic anatomy of diversity patterns / Scarponi D.; Kowalewski M.. - In: PALEOBIOS. - ISSN 0031-0298. - STAMPA. - 25 supp. 2:(2005), pp. 103-104. (Intervento presentato al convegno North American Paleontology Convention 2005 tenutosi a Dalhousie University, Halifax, Nova Scotia Canada nel June 19-26 2005).
Sequence stratigraphic anatomy of diversity patterns
SCARPONI, DANIELE;
2005
Abstract
The influence of sequence stratigraphic (sea-level driven) processes on patterns derived from the fossil record is receiving increasing attention. This study explores stratigraphic anatomy of diversity patterns across two late Quaternary 4th order sequences deposited on the Po Plain (Italy) over the last 150 k.y. (i.e., the two most recent glacial-interglacial cycles). The rich mollusk fauna, dominated by extant forms, preserved as a part of well-understood eustatic cycles, offers a testing ground for exploring how climate-driven sea level changes influence sample diversity, diversity turnover, and higher-order diversity patterns within and across systems tracts and sequences. These two 4th-order depositional sequences were densely sampled from three cores. The data (150 species and 22776 specimens from 29 Holocene and 19 Pleistocene samples) were analyzed using single-sample and multi-sample rarefaction techniques. In all three cores and for both cycles, sample-level diversity decreased upward within sequences: the late Transgressive Systems Tract (TST) samples displayed the highest equitability and richness and the Highstand Systems Tract (HST) samples displayed the lowest diversity (the trend primarily reflects the increase in the dominance of most common species in HST samples). This pattern is likely due to a combination of ecological, environmental, and taphonomic processes. Multi-sample rarefaction indicates that species turnover is more limited in transgressive phases of both depositional cycles. This trend may reflect increasing environmental heterogeneity of marginal habitats averaged within shallowing-upward successions and/or decreasing time averaging associated with increasing sedimentation rates during HST phases of the cycles. The sequence and multi-sequence diversity levels are lower than those observed within individual late-TST systems tracts, indicating that species turnover was minimal both within as well as across the last two glacial-interglacial cycles. The study shows that species richness and equitability patterns of the most common mollusk species track closely the sequence stratigraphic architecture of late Quaternary successions of Po Plain.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
