Adam D. Woods , California State University (Fullerton)
Support from PRF allowed the completion of the following tasks during 2010-2011:
a) Determination of trace element data related to Early Triassic paleoproductivity and paleoxygenation from the Ursula Creek locality.
b) Collection of total organic carbon (%TOC) and total carbonate carbon (%TIC) data from the Ursula Creek locality.
c) Completion of two undergraduate theses (Keffer and Wakefield).
Much of 2010-2011 was spent collecting %TOC and %TIC data and trace element data from samples collected from the Ursula Creek locality in eastern British Columbia that were collected in May, 2010. Ryan Wakefield collected %TOC and %TIC data from samples from the Ursula Creek locality during the summer and fall of 2010, and completed his undergraduate thesis in December 2010. Sean Keffer was trained on the ICP-AES, and collected trace element data related to paleoproductivity, paleoxygenation and sedimentary characteristics of the samples for his thesis during the Fall of 2009 and Spring of 2010 from a drill core (A8-7-85/18w6) from the Pedigree-Ring Border-Kahntah River area in the northern Peace River Basin, the central sub-basin of the WCSB. This data was used to complete Keffer's undergraduate thesis in December 2010. Nate Liodas collected total organic carbon (%TOC) and total carbonate carbon (%TIC) data from samples from the same drill core as Keffer for his undergraduate thesis, which he completed in December 2009. Three new undergraduate students (Elizabeth Agredano, Julie Ortiz, and Robert Sia) are currently working on additional previously-collected core samples from the Pedigree-Ring Border-Kahntah River area in the northern Peace River Basin, and will collect trace element data using a recently-acquired ICP-OES. Agredano, Ortiz, and Sia plan on completing their undergraduate theses in Spring or Summer 2012. Trace element and %TOC and %TIC data collected by students and the PI will provide a means to examine temporal and spatial changes in paleoproductivity and paleoxygenation across a wide latitudinal swath of western North America during the Early Triassic.
Trace element and %TOC and %TIC data has been, or will be collected from samples from three outcrop localities (Opal Creek in the southernmost subbasin of the WCSB, the Spray River Basin, Cadomin in the central subbasin of the WCSB, the Peace River Basin and Ursula Creek, from the northern part of the Peace River Basin), and from multiple drill cores from the Pedigree-Ring Border-Kahntah River area in the northern Peace River Basin. In general, results suggest that productivity collapsed at the Permian-Triassic boundary, but recovered quickly in the Griesbachian (earliest Triassic). Productivity remained robust through the remainder of the Early Triassic based on trace element data from Ursula Creek, Opal Creek, and Cadomin. These results are further supported by trace element and %TOC and %TIC data from one core (A8-7-85/18w6) from the Pedigree-Ring Border-Kahntah River area that samples sedimentary rocks deposited across the Dienerian-Smithian boundary (middle Early Triassic). In addition, the typically organic-rich nature (typically 3-5% TOC) of shales and siltstones from other drill cores from the Pedigree-Ring Border-Kahntah River area is further evidence of a rapid, sustained recovery of primary producers following the Permian-Triassic mass extinction. Results from Opal Creek are indicative of deposition under suboxic to anoxic conditions from the Permian –Triassic boundary through the Griesbachian, after which deposition occurred under oxic conditions for the remainder of the Early Triassic. These results differ from the Cadomin locality where periods of enhanced paleoproductivity correlate with periods of low oxygenation across much of the Early Triassic, suggesting that productivity may have been a primary control on benthic oxygenation for this area. Sedimentary rocks in the Cadomin area were deposited at shallower depths than those from Opal Creek, Ursula Creek, or the Pedigree-Ring Border-Kahntah River area, which may reflect the Cadomin locality being closer to the locus of upwelling, or may be due to local paleobathymetric variations. Trace element data from the Pedigree-Ring Border-Kahntah River area (from core A8-7-85/18w6) are indicative of suboxic conditions and higher primary productivity during periods of higher sea level as reflected by laminated silty shales, and deposition under oxic conditions during periods of lower sea level, as reflected by turbiditic and hummocky cross-stratified sandstones. Overall, the data from the Pedigree-Ring Border-Kahntah River area suggests that shifts in the redoxocline closely tracked rising and falling sea levels. Continued analysis of trace element data from samples collected elsewhere from the WCSB should shed further light on the interplay between productivity, paleoxygenation, and sea level during the post-extinction interval.
This research has positively impacted the PI by allowing him to expand his research interests and knowledge beyond his previous expertise (primarily the sedimentology and petrography of unusual Lower Triassic carbonates) and by fostering collaborative relationships with several international colleagues (Tyler Beatty, J.-P. Zonneveld, Charles Henderson). The undergraduate students involved with the research have learned technical and analytical skills that they would not likely have obtained otherwise, and are collecting and interpreting data related to a large, multidisciplinary problem. In addition, the students have the opportunity to interact with other researchers, potential graduate advisors, and future employers when they present their data at national and regional meetings. Keffer, Liodas, and Wakefield presented their results at the 2010 Cordilleran Section of the Geological Society of America meeting in May 2010, and Agredano, Ortiz, and Sia will be encouraged to present the results of their research at a future national or regional meeting.