Joint Meeting Pacific Section, AAPG & Cordilleran Section GSA April 29–May 1, 2005, San José, California
Stratigraphic Framework and Reconstruction of the Windermere Turbidite System: A Neoproterozoic Passive Margin Depositional System
Gerald M. Ross
Kupa'a Farm, Box 458, Kula, HI 96790, [email protected]
The Windermere Supergroup (WSG; Neoproterozoic 740-570 Ma)in the southern Canadian Cordillera is characterized by widespread preservation of deep-water facies which includes basin floor and slope turbidite systems. The Windermere turbidite system developed along the ancestral continental margin of the Pacific Ocean and overlies rift facies at the base of the WSG that developed during the breakup of Rodinia. The regional distribution of stratigraphic elements and the vertical shoaling from basin floor into shelf, over a stratigraphic thickness of 9 km, suggests that the Windermere turbidite system developed along a passive margin, making it unique (?) in the geologic record. The Windermere turbidite system has been correlated throughout the southern Canadian Cordillera on the basis of several through-going marker units, including a deep-water post-glacial cap carbonate dated directly (Re-Os) at circa 609 Ma and several deep-water carbonate units. The reconstructed size of the turbidite system is at least 160,000 km2, comparable in scale to modern passive margin turbidite systems such as the Amazon and Mississippi fans. Using the deep water cap carbonate as a regional timeline basin floor facies can be traced over 200 km basinward from discrete channel systems hosted in mud-rich facies to mud-poor stacked sand-rich facies with very low relief channels/lobes. Overlying slope facies, distinguished by increased mud content and abundance of shelf-derived debris flows, consists of conglomerates within well developed meandering channel-levee systems. Passive margin turbidite systems are amongst the most common of modern offshore petroleum plays but also carry the greatest risk. The combination of extensive periglacial outcrop, cliff sections, and throughgoing stratigraphic markers make the Windermere turbidite system an outstanding laboratory for the analysis of stratigraphic patterns and internal complexities of modern prospective turbidite systems.
Posted with permission of The Geological Society of America; abstract also online (http://gsa.confex.com/gsa/2005CD/finalprogram/abstract_85841.htm). © Copyright 2005 The Geological Society of America (GSA).