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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
DOI: 10.1306/10261817348
Late Mesozoic sediment provenance on Georges Bank: Enlargement of river drainages to the Atlantic Ocean in the Late Jurassic–Early Cretaceous
Isabel Chavez,1 Georgia Pe-Piper,2 David J. W. Piper,3 and R. Andrew MacRae4
1Department of Geology, Saint Mary’s University, Halifax, Nova Scotia, Canada; [email protected]
2Department of Geology, Saint Mary’s University, Halifax, Nova Scotia, Canada; [email protected]
3Natural Resources Canada, Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada; [email protected]
4Department of Geology, Saint Mary’s University, Halifax, Nova Scotia, Canada; [email protected]
ABSTRACT
The detrital mineralogy of Upper Jurassic to Lower Cretaceous sandstones from the Continental Offshore Stratigraphic Test G-2 well in the Georges Bank Basin was studied to better understand the varying supply of clastic sediment to the basin. Heavy minerals separated from cuttings were identified by chemical analyses, zircons were dated, and Raman spectroscopy was applied to identify titania polymorphs (rutile, anatase, and brookite). Upper Jurassic (Oxfordian) sands contain tourmaline, fluorapatite, Mn-almandine and grossular garnets (derived from the central Maine and coastal Maine belts), and pumice and trachytes reworked from volcanics in the Long Island platform. Zircon geochronology (300–450 and 550–700 Ma) supports sources from peri-Gondwanan Appalachian terranes. Lower Cretaceous heavy minerals show that Oxfordian supply was diluted to 30%, mostly by additional ilmenite, zircon, tourmaline, and staurolite, probably by components from central and northern Maine and New Brunswick. Rutile and anatase from metapelites are more common than in the Oxfordian, where mafic igneous sources predominate. Lower Cretaceous zircons include a few Mesoproterozoic grains that might be reworked from middle Paleozoic sedimentary rocks in the Gander terrane of northern Maine and New Brunswick, although subhedral grains together with rare chromite may indicate minor or intermittent supply from the Sable River draining Labrador. Heavy minerals provided important provenance information not available from zircon geochronology alone. Progressive enlargement of the catchment area resulted from an increasingly humid climate in the latest Jurassic and active mostly northeast-trending faults in the Early Cretaceous. This resulted in greater supply of petrographically more-mature sand to the basin.
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