Geology and neotectonism in the epicentral area of the 2011 M5.8 Mineral, Virginia, earthquake

Field Guides
By: , and 

Links

Abstract

This fi eld guide covers a two-day west-to-east transect across the epicentral region of the 2011 M5.8 Mineral, Virginia, earthquake, the largest ever recorded in the Central Virginia seismic zone. The fi eld trip highlights results of recent bedrock and surficial geologic mapping in two adjoining 7.5-min quadrangles, the Ferncliff and the Pendleton, which together encompass the epicenter and most of the 2011–2012 aftershocks. Tectonic history of the region includes early Paleozoic accretion of an island arc (Ordovician Chopawamsic Formation) to Laurentia, intrusion of a granodiorite pluton (Ordovician Ellisville pluton), and formation of a post-Chopawamsic successor basin (Ordovician Quantico Formation), all accompanied by early Paleozoic regional deformation and metamorphism. Local transpressional faulting and retrograde metamorphism occurred in the late Paleozoic, followed by diabase dike intrusion and possible local normal faulting in the early Mesozoic. The overall goal of the bedrock mapping is to determine what existing geologic structures might have been reactivated during the 2011 seismic event, and surfi cial deposits along the South Anna River are being mapped in order to determine possible neotectonic uplift. In addition to bedrock and surfi cial studies, we have excavated trenches in an area that contains two late Paleozoic faults and represents the updip projection of the causative fault for the 2011 quake. The trenches reveal faulting that has offset surfi cial deposits dated as Quaternary in age, as well as numerous other brittle structures that suggest a geologically recent history of neotectonic activity.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Geology and neotectonism in the epicentral area of the 2011 M5.8 Mineral, Virginia, earthquake
Series title Field Guides
DOI 10.1130/2014.0035(04)
Volume 35
Year Published 2015
Language English
Publisher Geological Society of America
Contributing office(s) Eastern Geology and Paleoclimate Science Center
Description 24 p.
First page 103
Last page 127
Country United States
State Virginia
City Mineral
Google Analytic Metrics Metrics page