Abstract

Upper Jurassic to Lower Cretaceous synrift sandstones from two industry exploratory wells in the Flemish Pass Basin were studied for provenance using heavy mineral proxies. These sandstones were deposited during the North Atlantic rifting stage, at which time rifting intensified between Iberia and the Grand Banks. Several heavy mineral methods were used, including in-situ U-Pb geochronology and morphological and chemical analysis of detrital zircons, chemical discrimination of detrital tourmalines, and heavy mineral ratios.

Clastic bed-load material entering the northern Flemish Pass Basin during the Tithonian to Berriasian was connected to transport systems reaching west, as far as 400 to 500 km (249–311 mi). Source areas to the west included igneous rocks and associated cover sequences of the Avalon zone, as well as the magmatic rocks, metasedimentary rocks, and associated cover sequences present in the Central mobile belt. The eastward-directed input of bed-load material into the basin is considered to have resulted in the concentration of sandstone units along its western margin, with deteriorating reservoir grade toward the east. Given the regional extent of drainage systems, it is likely that similar constraints apply to equivalent sandstones in the adjacent East Orphan Basin.

By the Valanginian–Barremian, paleodrainage orientations had switched and bed-load material began to enter the Flemish Pass Basin from more proximal areas to the southeast with the Avalon zone basement.

Overall, no evidence exists to support sediment sourcing from the Iberian margin or the Flemish Cap-Galicia Bank continental fragment to the east, and material from these areas is instead interpreted to have been shed into the incipient Atlantic Ocean or Bay of Biscay. Also, no evidence exists to support sourcing from Grenville basement farther to the west, implying that a drainage divide may have existed somewhere between central and western Newfoundland, west of which material was presumably being transported to the south or southwest.

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