CHRONOSTRATIGRAPHIC CONTEXT OF THE BIOTIC ASSEMBLAGES OF THE DAN RIVER-DANVILLE AND DEEP RIVER BASINS (NEWARK SUPERGROUP, VIRGINIA AND NORTH CAROLINA, USA)
The DRDB has the longest polarity stratigraphy and one that ties unambiguously to the NAPTS (1, 2) spanning nearly all three revised formations (in stratigraphic order: Walnut Cove, Dry Fork, Cow Branch) as well as the lower Stoneville Fm. Analysis of cores (NC Geol. Survey Repository) SO-C-2-81, CH-C-2-81, CH-C-1-81, and MO-C-4-81) from the DRB (2) show a remarkably close match in lithostratigraphy, down to the 20 ky precession cycle, corroborating magnetic polarity correlations and previous biostratigraphy based on fish (3).
Implications are: 1) the bulk of the Pekin Fm (DRB) is older than NAPTS chron E8, has no counterpart in the DRDB, correlates to the Falling Creek Fm of the Taylorsville basin and hence the Vinita Fm of the Richmond basin (4), and based on the NAPTS correlation to the European standard ages (5) must be Carnian in age and older than 227 Ma; 2) the Cumnock Fm. (DRB) and Walnut Cove Fm correlate with the Raven Rock Mb of the Stockton Fm (Newark basin) and are most simply interpreted as early Norian Age (225-227 Ma); 3) the Cow Branch Fm and “Lithofacies Assemblage II” (DRB) are late-early to middle Norian Age (217-222 Ma); and 3) lithofacies development and accumulation rate changes progressed synchronously in the two southern basins as well as the Newark basin during the Norian, suggesting tightly linked tectonic control on lacustrine development and/or direct linkages of the lakes themselves. All of the older major faunal and floral assemblages of the southern Newark Supergroup can now be placed in a tight temporal sequence, virtually independently of biostratigraphy.
Refs: 1 Kent & Olsen (1997) GSA Bull 109:366; 2 Whiteside et al. (2011) PNAS 108: 8972; 3 Olsen et al. (1982) AJS 282:1; 4 LeTourneau (2003) The Great Rift Valleys of Pangea in Eastern North America, Columbia Univ. Press 1, p. 12-58; 5 Muttoni et al. (2004) GSA Bull 116:1043.