Abstract 50788

VENDIAN-CAMBRIAN FAUNAS FROM THE SOUTHWESTERN U.S.

Presented by Hagadorn, James W..
Authors:
      Waggoner, Benjamin M..

Key words: Ediacaran, Cambrian, Vendian, Great Basin

In Session 102     Paleontology/Paleobotany IV: Origin and Diversification of Early Life on Earth Wednesday, 28-Oct-98 AM in Room: 701A at 10:15 AM for 15 minutes.

Abstract: Sparse occurrences of Ediacaran-style fossils have been documented from the lower member of the Wood Canyon Formation and the upper member of the Stirling Quartzite in the western Great Basin (Horodyski, 1991; Waggoner & Hagadorn, 1997). This fauna is of interest because it provides a paleobiogeographic link to similar occurrences in Namibia. Building on previous work, we document a variety of additional trace fossils from the same region, including additional occurrences of Gordia and Treptichnus (Phycodes) pedum from the lower Wood Canyon, and Planolites from the lower member of the Stirling. Several morphotypes of tubular fossils also occur in the lowermost Wood Canyon, including annulated cylindrical tubes, conical fossils, and helically twisted tubes which are square in cross section. Annulated tubes and conical fossils are preserved in epirelief in very fine sandstones, and may represent sabelliditids or cloudiniids. The helically twisted tubes are preserved as casts in siltstones and exhibit tetraradial symmetry a characteristic typical of scyphozoans. Helical twisting is also known in some anabaritids.

Fragmentary specimens of frondose Ediacaran soft-bodied fossils are also documented from the middle member of the Lower Cambrian Poleta Formation in the White Mountains, CA and from the upper member of the Lower Cambrian Wood Canyon Formation in the southern Kelso Mountains, CA. Based on similarities with fossils from the lower member Wood Canyon and from the Nomtsas Formation of Namibia, both specimens are tentatively interpreted as fragments of Swartpuntia sp. Fossils were collected in situ (by Wyatt Durham, Chris Fedo, and John Cooper) from strata containing diagnostic Lower Cambrian body and trace fossils. Additionally, in the Salt Spring Hills, CA, a discoidal fossil similar to Ediacaria was collected from the upper member of the Wood Canyon Formation. In light of Swartpuntia-like fossils documented from Lower Cambrian strata in Australia (Jensen et al., 1998), and proximity of Swartpuntia to T. pedum in the lower Wood Canyon Formation and in Namibia (Narbonne et al., 1997), Swartpuntia may be an example of an Ediacaran holdover taxon in the Lower Cambrian.