Paper No. 13
Presentation Time: 4:00 PM


KELLEY, Brian M.1, YU, Meiyi2, LEHRMANN, Daniel J.3, JOST, Adam B.1, LAU, Kimberly V.1, SCHAAL, Ellen K.1, LI, Xiaowei4 and PAYNE, Jonathan L.1, (1)Department of Geological and Environmental Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, CA 94305, (2)College of Resource and Environment Engineering, Guizhou University, Guiyang, 550025, China, (3)Geoscience, Trinity University, San Antonio, TX 78212, (4)Department of Geological Sciences, University of Texas at El Paso, 500 West Avenue, El Paso, TX 79968,

The pattern of reef ecosystem recovery from the end-Permian extinction is poorly constrained due to the limited stratigraphic, spatial, and geographic range of reef buildups in Early Triassic and Anisian (early Middle Triassic) strata. In this study, we combined field studies and petrographic analysis to examine the pattern of reef evolution in latest Permian to Late Triassic carbonate platforms in the Nanpanjiang Basin of South China, an area of extensive shallow-water carbonate deposition in the tropical eastern Tethys.

We find that early Mesozoic reef recovery in the eastern Tethys was a five-step process: (1) in the immediate aftermath of extinction, calcimicrobial biostromes (P/T boundary microbialites) developed in shallow-water platform settings; (2) in late Induan time, biohermal stromatolites developed in platform interior settings; (3) in latest Spathian time, large-scale Tubiphytes, microbial, and cement reefs lacking skeletal metazoans initiated on the margins and steep upper slopes of carbonate platforms, signaling the return of reefs to platform-margin settings; (4) in the Aegean or Bithynian (early Anisian), diminutive (mm-scale) calcareous sponges and calcareous algae appeared in the Tubiphytesreef, marking the reappearance of skeletal metazoans and calcareous algae to reefs in the eastern Tethys; and (5) in the late Anisian, the appearance of scleractinian corals coincided with increased abundance, size, and diversity of metazoan and algal reef builders.

Early Mesozoic reefs of the eastern Tethys were dominated by microbes, Tubiphytes, and early-marine cements until the late Anisian, several million years into the Middle Triassic. The appearance of small metazoan buildups in Early Triassic strata in other parts of the world indicates that potential reef-building organisms were present much earlier. The limited stratigraphic range of those buildups, however, reinforces the interpretation that episodic environmental disturbances such as euxinia, high temperatures, and acidification impacted biotic recovery during Early Triassic time. Our findings of protracted early Mesozoic reef recovery suggest that the causal links between environmental disturbance and biotic recovery extended into Middle Triassic time.