Tracing the roots and drivers of the Cambrian Explosion - Dr. Rachel Wood
Автор: Virtual Seminars in Precambrian Geology
Загружено: 2021-04-14
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Tracing the roots and drivers of the Cambrian Explosion
Dr. Rachel Wood
I would like to consider three different, but related, strands to understanding the late Ediacaran to early Cambrian rise in metazoan diversity. First, I explore terminal Ediacaran skeletal taxa that may represent bilaterians – so making a connection between the Ediacaran-Cambrian biotas. Second, the heterogeneity of terminal Ediacaran environments is evident, but what controls redox distribution regionally? We have combined iron (redox) and phosphorus speciation data (nutrients) with an inventory of biotic diversity and distribution from the Nama Group, Namibia (~550 to ~538 Ma). These show that unstable marine redox dominates initially, but a marked deepening of the redoxcline is recorded from ~547 Ma onwards, with full ventilation of the outer ramp by ~542 Ma. These data that show a long-term decrease in nutrient delivery from continental weathering, coupled with a possible decrease in upwelling, may have led to the gradual ventilation of the Nama Group basins, so promoting the development of stable oxic conditions and the radiation of new mobile taxa. Finally, I explore how different metrics of metazoan complexity through the early Cambrian such as biodiversity, body size, origination and extinction rates might be useful for understanding evolutionary dynamics and response to dynamic redox.
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