Mesozoic Transgressions in Sverdrup Basin: ABSTRACT

Abstract

Three major Mesozoic transgressions have been recognized in the Sverdrup basin. The first started in earliest Triassic and culminated during Late Triassic (Norian). A sequence of sands, silts, and clay, with a maximum known thickness of 17,800 ft was deposited during this time. The second transgression started in Early Jurassic (Sinemurian) and ended in Early Cretaceous (Neocomian), leaving a sandstone-shale sequence with maximum known thickness of 5,000 ft. The last marine transgression began during Early Cretaceous (Valanginian?) culminating in Albian time; the regressive phase ended in Late Cretaceous (early Senonian) when the seas retreated entirely from the basin. Maximum inferred thickness of the sandstone-shale sequence deposited is of the order of 8,000 ft. At the close of Cretaceous, rejuvenation of the source areas resulted in the deposition of a thick sequence of continental clastics. This, the last major sedimentary cycle recorded in the basin, came to an end during the early Tertiary. Clastic distribution indicates southern and eastern sources for the Triassic sediments, with suggested open marine conditions on the north and northwest. Similar conditions may be inferred for the Jurassic and Cretaceous sediments in the eastern part of the basin. However, in the central and western areas the clastic distribution presents some problems. Apparently this distribution was controlled by some epeirogenic events of intra-Jurassic age which affected mainly the northwestern parts of the basin. These events appear to have caused temporary interruptions of the sedimentary processes during the second transgressive cycle. End_of_Article - Last_Page 2485------------