2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 3
Presentation Time: 8:50 AM

ICHNOLOGY OF THE LOWER TRIASSIC BLIND FIORD & BJORNE FORMATIONS, SVERDRUP BASIN, ARCTIC CANADA


ZONNEVELD, John-Paul, Geological Survey of Canada, Calgary, AB T2L 2A7, Canada and BEATTY, Tyler W., Applied Stratigraphy Research Group, Dept. of Geology and Geophysics, University of Calgary, 2500 University Drive N.W, Calgary, AB T2N 1N4, jzonneve@nrcan.gc.ca

Lower Triassic strata in the Sverdrup Basin are represented by basin-center shale, & minor sandstone of the Blind Fiord Formation & basin-margin sand-dominated successions of the Bjorne Formation. Both units are dominantly siliciclastic successions that interfinger extensively reflecting a series of three major marine transgressions & regressions. The Bjorne-Blind Fiord succession rests upon chert, shale & siliceous siltstone of the Van Hauen & Lindstrom Formations. This contact is conformable in the basin center & erosional on the basin margins. Trace fossil assemblages within these strata provide unique insight into the health of infaunal communities during the Permian-Triassic biotic crisis & the Early Triassic recovery interval on the northern margin of Pangaea.

Latest Permian successions in the Sverdrup basin are dominated by proximal offshore through lower shoreface successions containing a moderately diverse suite of traces including Asterosoma, Phycosiphon, Scalarituba, Skolithos, Thalassinoides & exceptionally large Zoophycos.

Early Triassic proximal offshore & offshore transition successions, preserved in basin center settings, contain few trace fossils. Those that do occur are small, horizontal feeding traces (Planolites & Helminthopsis). Exceptions occur within event beds transported from shallower settings including (Asteriacites & Kouphichnium). Early Triassic lower shoreface successions contain moderately diverse assemblages that include Arenicolites, Cruziana, Cylindrichnus, Diplocraterion, Lockeia, Palaeophycus, Siphonichnus, Thalassinoides & Spongeliomorpha. Although trace fossils were not observed in upper shoreface successions, intertidal flats contain a variety of trace fossils, particularly those constructed by molluscs (Beaconichnus, Gyrochorte, Lockeia, Neonerites & Protovirgularia).

Early Triassic fluvially-dominated successions include Cochlichnus, Fuersichnus, Lockeia, Skolithos, rare tetrapod footprints & a wide range of insect brooding traces. Comparison of these trace fossil assemblages with those from similar environmental settings in coeval western & northern Canadian successions suggests that environmental constraints limited infaunal diversity primarily distal of the lower shoreface.