Reports

Exposed Triassic Basins as Proxies for the Understanding of Buried Rift Successions

2021, Brezinski, D.K., and Kavage Adams, R.

Report of Investigations 88

Executive Summary

• Study of rocks exposed in the Culpeper and Gettysburg rift basins provides a foundation for the understanding of buried rift basin stratigraphic successions.
• Recurrent assemblages of rock types are interpreted as representing genetic packages of lithologies herein termed lithofacies associations.
• Five distinct lithofacies associations are recognized, each consisting of aggregated lithologies formed within overlapping depositional systems.
• Named Lithofacies Associations A through E, these groups of lithologies were interpreted to have formed in alluvial fan, braided stream, meandering fluvial, proximal, and distal lake settings.
• When the five lithofacies associations are applied to rocks of the buried Taylorsville basin a revised depositional architecture is elucidated.
• The lithofacies associations approach illustrates that deposition within Triassic rift basins did not form the layer cake geometries commonly portrayed, but rather laterally intergrading alluvial, fluvial, and lacustrine processes from basin margin to center.
• This revised internal stratigraphy provides insight as to areas suitable for long–term carbon dioxide (CO2) sequestration within the coarse-grained, fluvial lithofacies associations that are concealed beneath thick intervals of fine-grained lake strata.
• Thick intervals of concordant extrusive and intrusive mafic igneous rocks also provide potential CO2 reservoirs owing to the primary porosity within lava flow vesicles, and fracture porosity produced by the rapid cooling and contraction of the lava flows and magmatic intrusions.

Downloads and Data

Report of Investigations 88 (pdf, 26 MB)