EARLY CRETACEOUS POSTRIFT EVOLUTION OF THE EASTERN NORTH AMERICAN MARGIN: INSIGHTS FROM THE NEW ENGLAND-QUEBEC IGNEOUS PROVINCE

The Early Cretaceous New England-Quebec (NEQ) igneous province represents an important episode of postrift magmatism and associated brittle deformation of the upper crust along the Eastern North American Margin (ENAM). The province, consisting of sheet intrusions and small plutons, has traditionally been linked to passage of the Great Meteor hotspot, yet several investigators have argued against this hypothesis. Here, we present ⁴⁰Ar/³⁹Ar ages for four NEQ dikes and an LA-ICP-MS U-Pb pluton age that confirm Early Cretaceous magmatism spanned at least 35 Ma within the New England portion of the NEQ. The duration of magmatism for this region and small shift in location (~100 km) are inconsistent with a hotspot origin.

The new age data are part of an ongoing investigation using geochronology, geochemistry, and paleostress analysis to understand the role of the NEQ in ENAM passive margin development. The NEQ coincides with the largest of three low velocity mantle anomalies beneath the Appalachians. Major and trace element geochemical results for NEQ sheet intrusions indicate trace element patterns are similar to the Late Jurassic and Eocene postrift intrusions of Virginia/West Virginia. Mesoscale normal and strike-slip faults occur throughout the study area. The sheet intrusion ages in combination with the fault-slip data provide evidence for a changing stress field and extension associated with NEQ magmatism.