--> Abstract: Lower Triassic Shallow Marine Ichnofossil Assemblages from the Northwest Margin of Pangea: Insight into Biotic Recovery after the Permian-Triassic Mass Extinction, by Tyler W. Beatty, John-Paul Zonneveld, Charles M. Henderson, and Robert B. MacNaughton; #90039 (2005)

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Lower Triassic Shallow Marine Ichnofossil Assemblages from the Northwest Margin of Pangea: Insight into Biotic Recovery after the Permian-Triassic Mass Extinction

Tyler W. Beatty1, John-Paul Zonneveld2, Charles M. Henderson3, and Robert B. MacNaughton2
1 University of Calgary, Calgary, AB
2 Geological Survey of Canada, Calgary, AB
3 Department of Geology and Geophysics, University of Calgary, Calgary, AB

The Permian – Triassic boundary interval saw unparalleled extinction in the marine realm, with indications of 95% loss at the species level. This resulted in extensive restructuring of communities. Lowest Triassic ichnofossil assemblages from the northwest margin of Pangea indicate diachroneity in benthic community recovery between lower, middle and higher latitude settings. Notably, moderately diverse, shallow water benthic communities are recorded in the Griesbachian Toad Formation (southeast Yukon), lower Montney Formation (Alberta subsurface) and lower Sulphur Mountain Formation (Canadian Rockies). Ethologies represented within these units include: cubichnia (Lockeia); domichnia (Diplocraterion, Skolithos, Spongeliomorpha, Thalassinoides); repichnia (Cruziana, Diplichnites); pascichnia (Helminthopsis); and fodichnia (Planolites, Palaeophycus, Teichichnus, Rhizocorallium). Arthropods were a dominant component of the infauna. In higher-latitude deposits such as the Blind Fiord and Bjorne formations of the Sverdrup Basin (ca. 50° paleolatitude) ichnofossil assemblages are less diverse and represent less complex ethologies (i.e. Planolites, Palaeophycus, Teichichnus, and Bergaueria). Likewise, in lower-latitude settings, such as the Dinwoody Formation in southeast Idaho and Utah (ca. 15° paleolatitude), diversity and behavioural complexity are low throughout much of the Griesbachian.

In the Tethyan region, shallow-marine ichnofossil diversity and complexity were reportedly low throughout the Griesbachian, and slowly increased into the Spathian. The disparity between western Pangean, mid-latitude ichnofauna and those of lower and higher latitudes, or those of the Tethyan region, suggests the presence of ecological refugia along parts of the western Pangean coast. The location of these refugia may reflect latitudinal control on the timing of recovery.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005