Giant Submarine Landslide Triggered by Paleocene Mantle Plume Activity in the North Atlantic

Abstract

The 310 km long, mid-Paleocene ‘Halibut Slide’, is one of the largest submarine landslides on Earth, and the largest known in an epicontintental setting. Approximately 62 Ma, plume-related uplift in the North Atlantic caused instability of Cretaceous chalk slopes across the North Sea Basin. The Danian-aged Halibut Slide (HS) is suggested to be a consequence of this major tectonic event. Basal megascours, up to 1 km wide, 200 m deep and 70 km long, indicate synchronous triggering of tributary slides from intra-shelf Mesozoic highs, with the slide confluence occurring at the southern margin of a major intra-basinal high, the Halibut Horst. The megascours were formed by up to 1 km wide and 140 m tall chalk megaclasts that are shown to out-run the main slide body by up to 10 km. The basal shear surface (max ~1.6^°) of the slide significantly modified the shelf to slope profile. The HS is confined down-dip by remnant Mesozoic rift topography on the basin floor. A splay from the HS forms the Montrose Slide (MS), with both of the slides covering an area of ~7000 km². This major slope-grading event heralded the termination of 40 Ma of chalk deposition in the basin. Throughout the rest of the Paleocene, sediment transfer from the shelf to the basin was dominated by siliciclastic turbidity currents. Turbidite system routing was strongly affected by the topography created by both of these slides. The discovery of this major submarine landslide provides new insights into the response of sedimentary systems to regional tectonic events.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018