The eastern North American continental margin was established during the Jurassic Period (about 145 to 200 million years ago) during the opening of the Atlantic Ocean and is thought to have remained tectonically stable since that time. However, recent evidence suggests tectonically driven uplift and erosion events occurred between 100 and 130 and between 15 and 2 million years ago, long after the rift episode. Similar events have been recognized on the margins of other continents bordering the Atlantic. The objective of this project is to determine the timing and spatial distribution of these events in eastern North America with the goal of establishing the relationship with events on other continents and, ultimately, provide constraints on possible tectonic mechanisms to explain synchronous events. The project will advance desired societal outcomes by the development of a grade 9-12 earth science module in collaboration with local schools with class visits and visits to Middlebury and intensive involvement of undergraduate students in research.
This project aims to understand rejuvenation of the Eastern North American margin, which remains virtually unknown compared to relatively well-documented rejuvenation events on the coasts of Africa, South America, Europe, and the north Atlantic. Preliminary data (increased sediment flux to the Baltimore Canyon Trough; thermochronology in the White Mountains, New Hampshire) suggest that at least three rejuvenation events occurred along the Eastern North American margin: Early Cretaceous (130-110 Ma), Late Cretaceous (85-65 Ma), and the Mio-Pliocene (15-0 Ma). Results from other Atlantic margins highlight two periods, the Late Cretaceous and Mio-Pliocene, in which rejuvenation may have occurred synchronously across multiple circum-Atlantic margins. This coincident timing raises the question of whether a common forcing mechanism can rejuvenate multiple passive margins at the same time? Two end-member hypotheses include: (1) lateral stresses transmitted long distances through the lithosphere, or (2) dynamic mantle stresses beneath passive margins (e.g. dynamic topography). On the large scale, a complete picture of which margins were synchronously rejuvenated and how they are geometrically related may be used to infer Atlantic-scale forcing mechanisms. On the local scale, delineating the spatiotemporal pattern of rejuvenation of the Eastern North American margin may reveal stress orientations or local fault mechanics, thus constraining the underlying forcing mechanism. This project uses both of these approaches to clarify the pattern of post-rift exhumation in the central Eastern North American margin (New England, New York, and New Jersey). The research team will determine time-resolved exhumation histories by using apatite and zircon U-Th/He and apatite fission track thermochronology in bedrock drill cores and sediment provenance using trace element composition of heavy minerals and U-Pb dating of zircon and rutile and provenance of sediments in offshore drill cores from the Baltimore Canyon Trough. These two approaches are complementary; thermochronology provides the timing and magnitude of exhumation at a point, whereas detrital provenance integrates a broad range of possible source regions and can detect exhumation events too small to reset thermochronometers.
