THE CACHE CREEK TERRANE: A LOOK AT THE OTHER SIDE OF THE PANTHALASSIC DURING THE PTB

The Cache Creek Terrane originated off the coast of North America during the late Paleozoic, and records deposition through the mid-Mesozoic, including the Permian-Triassic Boundary. The Permian-Triassic boundary is primarily defined by sites originating within the Tethys Ocean or coastal Pangaea, with few sampling locations originating in the Panthalasic Ocean. As most studies of the open Panthalassic Ocean during the Permian-Triassic boundary have focused on sites originating in western Panthalassa and accreted to Japan, the Cache Creek Terrane offers a unique perspective on the opposite side of the Panthalassic Ocean during and after the Permian-Triassic boundary. We will be focusing on three sampling locations from the Porcupine Creek site, spanning approximately 0.4 km. These sections consist primarily of fine-grained carbonate rocks, however there are other lithofacies not characteristic of an open ocean environment, such as oolites and argillites, suggesting a shallow setting close to a terrestrial sediment source. An analysis of the sedimentology and stratigraphy of the Cache Creek Terrane will provide valuable information about depositional environments within the Panthalassic Ocean prior to and during the Permian-Triassic boundary. We will use isotope ratio mass spectroscopy, as well as major and trace element geochemistry, in order to reconstruct environmental conditions at the time of deposition. With this we will look at the depth of the chemocline, and the level of dolomitization within the terrane. Constructing a fence diagram from our three sampling sites, we will use sequence stratigraphy and biostratigraphy to analyze the paleoenvironment during deposition. We will be looking into the source of clay to the open ocean environment, relative sea level around the Cache Creek Terrane, and the changes to the environment through time. With this study we hope to help complete the picture of the conditions around the Permian-Triassic boundary.