BLOWING IN THE JURASSIC WIND: PALEOGEOGRAPHY AND HYDROGEOLOGY OF EOLIAN SANDSTONES FROM THE HARTFORD, POMPERAUG, AND ARGANA (MOROCCO) RIFTS

Our recent discoveries of aeolian sandstones in the Hartford (HB), Pomperaug (PB), and Argana (Morocco) basins reveal important information on the paleoclimate during the incipient breakup of Pangea, as well as the distribution of high porosity and high permeability strata in the Triassic-Jurassic rift system in eastern North America and North Africa. As the southern-most aeolian beds in the Newark Supergroup, the HB-PB occurrences provide essential constraints on the paleoclimatic zones and the paleogeography of sandy deserts within the early Mesozoic rift system. The precise location of aeolian beds, along with coals and other climate-sensitive rocks, in stratigraphic and paleogeographic space suggests that the early Mesozoic climate belts were strongly zonal, with a narrow equatorial zone and a broad arid to semi-arid zone.

Furthermore, the identification of regional-scale aeolian beds locates important bedrock aquifers. Due to sorting and mineral segregation during deposition, the aeolian beds have the highest porosity and permeability of any sedimentary rocks tested in the Newark rifts. In the PB alone, the aeolian strata have the potential to hold billions of gallons of groundwater for a suburban region that is dependent on bedrock wells for water supply. Identification of the geographic distribution of the aeolian strata is critical for municipal land-use management and environmental protection of this unique resource. In the arid Argana Basin, the aeolian beds may have potential for a regional water supply aquifer.

Post-depositional hydrothermal copper mineralization is preferentially concentrated within the aeolian beds in both the HB and PB. The earliest Colonial copper mines exploited malachite deposits hosted in aeolian beds at Newgate in Suffield, Connecticut, where the famous Higley Coppers, the first coins minted in America, were produced. Due to their particular color, grain size, and texture, the world-famous brownstone quarries in Portland Connecticut and Longmeadow Massachusetts were specifically located in aeolian-rich sandstone sequences. Operating in the late 19th and early 20th centuries, the Portland and Longmeadow quarries produced prolific quantities of red-brown sandstone that defined the architectural style of major cities along the eastern seaboard.