The stratigraphy and structure of the Laurentian Cone region

Abstract

A series of single and multichannel seismic reflection profiles combined with well data from the adjacent shelves and deep sea and published geophysical profiles permit the reconstruction of the geologic development of the Laurentian Cone. The cone's sediments can be divided into two megasequences, a lower one of Early Jurassic to Eocene age, which extends from a transitional and oceanic basement to horizon AT, and an upper sequence of early-middle Miocene to Holocene age extending from horizon AT to the sea floor. Plastic flow of Early Jurassic salt at the base of the lower megasequence has resulted in the deformation of the strata above, and the formation of a ridge that extends along the continental rise from Georges Bank to the Grand Banks. Horizon AT, separating the two sequences, is the surface of a fan deposited by turbidity currents during a latest Cretaceous and a late Eocene–Oligocene regression; these regressions may be due to the onset of continental glaciation. Deposition of this regressive wedge initiated the emplacement of the Laurentian Cone. The upper terrigenous megasequence, composed of three coalescing fans, was emplaced through the action of turbidity currents, and reflects the rapidly fluctuating climatic conditions associated with the waxing and waning of continental glaciers from latest Miocene to Holocene. The cone is not being supplied with sediments from the continent at present, but sediment continues to move down-cone in response to sporadic seismic activity.