Seismic evidence for a complex slide near the wreck of the Titanic: Model of an instability corridor for non-channeled gravity events

Abstract

The continental rise southeast of the Grand Banks of Newfoundland was surveyed many times during the last 8 years, especially during the search area for the wreck of the Titanic. High-resolution sidescan sonar images (système acoustique remorqué, SAR) have shown an area characterised by complex surficial morphology, referred to as in “instability corridor”. New seismic reflection profiling has shown that the instability corridor is more extensive than was previously believed and that it is the expression of the distal part of a large sediment slide. It consists of upslopedipping imbricated sediment blocks which are tens of metres thick and many kilometres in length. Downslope from the slide is an acoustically incoherent unit interpreted as comprising debris flow deposits which could represent the final phase of evolution of the slide. The slide is blanketed by 5–10 m of younger sediment. The upper part of this blanket has been recovered by coring and consists of foram ooze, thin sandy turbidites and muddy beds with mudstone clasts. Radiocarbon dating and foram assemblages show that the upper metre of the core is late Holocene in age, with about eight resedimented beds forming in the last 4000 years. These recent turbidity currents cut erosional furrows and refresh the pre-existing steps of the slide. Three phases characterise the evolution of the instability corridor: (1) the major event involving a giant slide of bedded sediments up to 100 m thick, with a source probably on the steep continental slope of the Grand Banks 100 km to the north, (2) a draping of normal continental margin terrigenous sediments, and (3) erosion by one or a series of high-density turbidity currents. The giant slide created an instability corridor within which a number of channeled and non-channeled events took place during the late Holocene.