Quantitative Basin Analysis and Evolution of Deep-Marine Shale Basin, Middle Ordovician, Southern Appalachians: ABSTRACT

Abstract

A quantitative portrayal of paleobathymetry, rate of sedimentation, age, and crustal subsidence of a deep-marine shale basin not only reveals the timing and magnitude of geologic events but also has potential practical application in petroleum geology, as marine shales commonly are a primary source for hydrocarbons. A quantitative basin analysis of the Middle Ordovician Sevier Shale basin in east Tennessee was made using: (1) lithofacies interpretation, (2) conodont-graptolite biostratigraphy, (3) paleobathymetry, (4) rate of sediment accumulation, and (5) sediment backstripping through time. This analysis indicates three main phases of crustal subsidence: (1) an early tectonic and sediment loading phase with a subsidence rate of 3 to 4 cm/1,000 years; (2) a second tectonic phase with a subsidence rate of 60 to 65 cm/1,000 years; (3) a final sediment-loading phase with a subsidence rate of 4 to 15 cm/1,000 years. Five stages of basin evolution were involved: (1) stable-shelf stage, (2) downwarping stage, (3) starved-basin stage, (4) turbidite-fill stage, and (5) contour-current stage. On the basis of morphologic, stratigraphic, sedimentologic, and tectonic similarities between DSDP site 262 (Pliocene-Quaternary) in Timor and the Sevier basin, it is proposed that Sevier basin evolution may be considered analogous to foredeep basin development in Timor. This development occurred by concomitant basin subsidence and uplift of adjacent tectonic land owing to basinward migration of a topographic wave. End_of_Article - Last_Page 525------------