Paper No. 2
Presentation Time: 1:45 PM
RAPID RECOVERY OF PRIMARY PRODUCERS FROM THE LATE PERMIAN MASS EXTINCTION AND EARLY TRIASSIC PRODUCTIVITY-DRIVEN ANOXIA IN THE WESTERN CANADA SEDIMENTARY BASIN
The Late Permian extinction (LPE) was the most devastating biotic crisis in Earth history. Study of this event over the past 2 decades has revealed the interval of Earth history surrounding the LPE to be one of the most complex and biologically influential periods of the Phanerozoic. Many studies have examined the effect of the extinction on macrofaunal trends; attention has been focused recently on reconstructing primary productivity in the wake of the extinction and the possible effects that it may have had on the overall recovery. Recent evidence suggests that primary productivity was rapidly reestablished after the LPE and was likely amplified during the Early Triassic due to enhanced continental weathering and nutrient flux to the oceans (e.g., Algeo and Twitchett, 2010). Sedimentary rocks from the Western Canada Sedimentary Basin provide an excellent means to reconstruct paleoproductivity and examine its relationship to paleoenvironmental conditions across the entire Early Triassic. Proxies related to paleoproductivity (e.g., Cu, Ni, Zn), paleoxygenation (e.g., Mo, V, U), and sedimentological characteristics (e.g., Al, Ca, Mg) were collected from 2 outcrop localities that sample the LPE and the entire Early Triassic (Ursula Creek, BC; Cadomin, AB), and from a core that samples the Dienerian-Smithian boundary interval (A8-7-85/18w6) from the Pedigree-Ring Border-Kahntah River (PRBKR) area of northwestern Alberta and northeastern British Columbia. In addition, %TOC and %TIC data were collected from these study intervals as well as from 5 additional cores from the PRBKR area that sample the lower to middle Griesbachian (16-8-86/20W6, 16-33-84/18W6m, 16w6, B-24-B/9-H-16, C-74-E/94-H-16) and the Griesbachian – Dienerian (C-78-I/94-H-9). High levels of %TOC (typically 3-5%) coupled with Cu, Ni and Zn that are several times enriched above average shale values beginning a few cm above the LPE horizon indicate that productivity recovered rapidly and remained robust. High levels of productivity coupled with indicators of persistent anoxia in deeper-water, offshore facies suggest that anoxia was largely productivity-driven, and that high rates of primary productivity likely resulted in stresses that limited recovery to a narrow habitable zone along northwestern Pangea during the Early Triassic.