A new Early Jurassic (ca. 183 Ma) fossilLagerstättefrom Ya Ha Tinda, Alberta, Canada

Rowan C Martindale,Benjamin C Gill,Andrew H Knoll,Theodore R Them,Selva M Marroquín

doi:10.1130/g38808.1

Abstract

Lagerstatten —deposits of exceptionally preserved fossils—offer vital insights into evolutionary history. To date, only three Konservat-Lagerstatten are known from Early Jurassic marine rocks (Osteno, Posidonia Shale, and Strawberry Bank), all located in Europe. We report a new assemblage of exceptionally preserved fossils from Alberta, Canada, the first marine Konservat-Lagerstatte described from the Jurassic of North America. The Ya Ha Tinda assemblage includes articulated vertebrates (fish, ichthyosaurs), crinoids, crustaceans, brachiopods, abundant mollusks (coleoids with soft tissues, ammonites, gastropods, bivalves), wood, and microfossils. Paired bioand chemostratigraphies show that Lagerstatte deposition occurred during the late Pliensbachian through early Toarcian, capturing the carbon isotope excursion associated with the Toarcian Oceanic Anoxic Event. Therefore, the Panthalassan Ya Ha Tinda biota is coeval with Toarcian Lagerstatten from the Tethys Ocean (Posidonia Shale and Strawberry Bank). Comparisons among these deposits permit new insights into the diversity, ecology, and biogeography of Jurassic marine communities during a time of pronounced biological and environmental change (e.g., expanded subsurface anoxia, warming, and extinctions). They also highlight the possibility that Mesozoic Oceanic Anoxic Events are temporal foci of exceptional preservation.

Highlights

During the Early Jurassic there were several major environmental and ecological perturbations that influenced Mesozoic evolution, notably the Toarcian Oceanic Anoxic Event (T-OAE)
Ya Ha Tinda Biota At Ya Ha Tinda, exceptionally preserved fossils can be found in both the Red Deer and Poker Chip Shale members of the Fernie Formation (Fig. 2)
The Ya Ha Tinda Lagerstätte is contemporaneous with the Posidonia

Summary

INTRODUCTION

During the Early Jurassic there were several major environmental and ecological perturbations that influenced Mesozoic evolution, notably the Toarcian Oceanic Anoxic Event (T-OAE). The T-OAE is associated with benthic and pelagic extinctions including ammonites, fish, foraminifers, radiolarians, corals, bivalves, and brachiopods (e.g., Little and Benton, 1995; Lathuilière and Marchal, 2009; Caruthers et al, 2014; Caswell and Coe, 2014; Danise et al, 2015). Compelling as this record may be, it is biased; unbiomineralized organisms are rarely preserved, yet represent the majority of marine biodiversity (e.g., Schopf, 1978; Morris, 1986).

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RESULTS

DISCUSSION AND CONCLUSIONS