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Abstract

Early Cretaceous carbonate platforms were widespread and thick, and complex biotic associations formed reefs that contributed significant amounts of carbonate sediment. An analysis of three time slices, late Tithonian to early Valanginian, late Valanginian to early Aptian, and late Aptian to mid-Cenomanian, shows that although carbonate platform development increased throughout this span, it was stressed during the mid-Valanginian, the mid-Aptian, and the latest Cenomanian. These stress periods were also times when shallow-water rudists and calcareous algae experienced significant decline in abundance and diversity. These times of extinction were followed by diversification of new forms. The drivers of these stress events were a complex chain of events from increased rates of ocean-floor spreading, oceanic volcanism, increased and/or expanded anoxia within the ocean water column, increased nutrients and marine plankton productivity, and deposition of organic matter.

During the Early Cretaceous, carbonate platform ecosystems comprised a deeper-water association of mainly siliceous sponges, stromatolites, and some types of scleractinians and a shallow-water association of corals and rudists that built reefs and other structures. During the Aptian-Albian, intraplatform basins developed and their ramp margins generally were occupied by rudist-dominated associations of increasing biotic diversity.

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