Giant paleo-seafloor craters and mass wasting associated with magma-induced uplift of the upper crust.

Giant seafloor craters are known along many a continental margin with recurrent mass-wasting deposits. However, the impact of breakup-related magmatism on the evolution of such craters is barely understood. Using high-quality geophysical datasets, this work examines the genetic relationship among the location of magmatic sills, forced folds and the formation of giant paleo-seafloor craters underneath an ancient mass-transport complex in the Møre and Vøring basins, offshore Norway. The data reveal that forced folding of near-seafloor strata occurred because of the intrusion of several interconnected magmatic sills. Estimates of 1-dimensional uplift based on well data show that uplift occurred due to the intrusion of magma in Upper Cretaceous to Lower Eocene strata. Our findings also prove that subsurface fluid plumbing associated with the magmatic sills was prolonged in time and led to the development of several vertical fluid flow conduits, some of which triggered mass wasting in Neogene to Recent times. The repeated vertical expulsion of subsurface fluids weakened the strata on the continental slope, thereby promoting mass wasting, the selective cannibalization of the paleo-seafloor, and the formation of elongated craters at the basal shear zone of the mass-transport complex. Significantly, the model presented here proves a close link between subsurface magmatic plumbing systems and mass wasting on continental margins.

A simplified GIS and google-earth-based approach for lineaments and terrain attributes mapping in a basement complex terrain.

In this study, we use an integrated geologic mapping technique for remote mapping of lineaments and geologic terrain. Our workflow is based on geographic information system tools and consists of stream network delineation, lineaments mapping, terrain roughness index calculation, and interpretation of structural fabrics from google earth aerial photographs. The case study area, the Idanre Hills in southwestern Nigeria, has a protracted history and is characterized by steep-sided outcrops of a granitic batholith and migmatite-gneiss. Lineaments are widespread and dense around the batholith, occurring in areas of high elevation, and slope gradient. Terrain roughness indices are high at the outcrops and lineament sites. Streams in the area exhibit variable flow and partly align with the lineaments. The high roughness indices observed have tectonic connotations and are related to the occurrence of lineaments, strain domains, and high degree of rock weathering. Importantly, our method is effective in remote mapping of lineaments and terrain attributes within the study area and has wider applications in other basement complex terrains.