IGCP 668 Aims and Goals
The transition between Cambrian–Ordovician “boom and bust” episodes of evolution into Ordovician biodiversification and stabilization is a fundamental component of the evolution of the “Earth–Life” system. Evolutionary patterns in the later Cambrian seem to be tied to a peak in felsic magmatism, and the record of this magmatism is specifically concentrated in equatorial Gondwana, particularly in the Sibumasu block which has extrusive volcanics interbedded with fossiliferous strata. We are studying Sibumasu in the context of all relevant parts of Gondwana including Indo-China, North China, South China, Australia, India, Antarctica, and beyond in order to understand the "Earth-Life" system of this time. We are approaching this aim through a multidisciplinary approach incorporating:
Geochronology: Resolving the poorly understood late Cambrian and earliest Ordovician geochronology is necessary to interpret the cause and effect relationships between lithospheric events, atmospheric events, and extinction/biodiversification patterns.
Igneous petrology: Intrusive magmatism was widespread in the region during this interval, but its record is poorly understood. Sibumasu has the sole record of extrusive volcanism known from this region and contains numerous layers of volcanic tuff interbedded with fossiliferous sandstone beds ranging from the Jiangshanian (~492Ma) through the earliest Tremadocian (485Ma). These tuffs opportune a level of geochronologic resolution beyond what is currently available.
Stratigraphy (and stratigraphic subdisciplines): We are correlating the stratigraphy of Sibumasu and other parts of equatorial Gondwana using a combined approach of biostratigraphy, lithostratigrpahy, chemostratigraphy, magnetostratigraphy, and igneous petrology in order to more directly compare regional vs. local events and geochronologically calibrate all of equatorial Gondwana's Cambro-Ordovician history, not just that of Sibumasu where the absolute dates occur. Only though a coordinated approach of many disciplines and regions can causal relationships within the "Earth-Life System" be established.
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Palaeontology: When identifying speciation events, extinction events, and biodiversity levels, good taxonomy is fundamental. Although much progress has been made in updating classical systematics, additional taxonomic revision is urgently needed as efforts to update taxonomy have generally been isolated and scattered across limited taxa. Meanwhile, many new taxa have been established, some of which need to be evaluated for their taxonomic validity. As taxa are updated, integrating faunal occurrences into the Paleobiology Database (PBDB) and Geobiodiversity Database (GBDB) will make this information usable in addressing research questions at all scales
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