PROVENANCE OF THE TRIASSIC TO JURASSIC NEWARK SUPERGROUP DURING PROGRESSIVE RIFTING ALONG THE EASTERN NORTH AMERICAN MARGIN, USA

Abstract

The Late Triassic to Early Jurassic syn-rift basins, from the Grand Banks of Canada to Florida, record progressive extension prior to the breakup of Pangea and the opening of the north-central Atlantic. The early syn-rift strata are dominated by alluvial to fluvial conglomerates, sandstones, and siltstones. Unconformably overlying the early syn-rift strata are thick successions of lacustrine fine-grained sandstones, siltstones, and mudstones. While the latest syn-rift rocks contain fluvial and lacustrine lithofacies interbedded with Jurassic basaltic flows (CAMP). The proximal syn-rift lithofacies from multiple discrete basins are combined to form the Newark Supergroup. The deposition of the Newark Supergroup was accommodated in a series of individual half-grabens initiated along inherited Permo-Carboniferous reverse faults of the Appalachian-Veriscan Orogeny. Historically, the U.S. ENAM is considered a magma-rich continental rift margin; however, syn-rift deposition records ~30 Mya of progressive crustal thinning prior to CAMP magmatism and seafloor spreading. This study aims to reconstruct the provenance evolution of the syn-rift basins along the U.S. ENAM and elucidate the evolution of rifting by reconstructing the temporal and spatial drainage and sediment dispersal response to lithospheric rifting processes. Here we present the results of detrital zircon (DZ) U/Pb analyses of outcrop samples from the Hartford Basin. The upper Triassic New Haven Arkose Fm. consists of fluvial conglomerates, sandstones, and siltstones and new DZ U/Pb analyses show a major Pan-African component indicating an eastern source region. The lower Jurassic Berlin Fm. consists of lacustrine sandstones, siltstones, and mudstones interbedded with basaltic flows. DZ U/Pb analyses show a major Grenville component suggesting a provenance reversal. These new results combined with previous DZ U/Pb results from the Newark, Gettysburg, and Culpeper basins suggest two paleocatchment reorganizations occurred during progressive rifting of the U.S. ENAM. The first occurred in the Carnian and is likely related to a combination of crustal necking and rift-flank uplift. While the second reversal occurred in the Early Jurassic as a result of regional and local thermal uplift related to CAMP magmatism.