Description: The Grassi Detachment Fault is an Early Permian, low-angle extensional structure located in the Orobic Anticline. It separates the Variscan Basement in its footwall from the volcanic and sedimentary rocks of the Early Permian Collio Formation in its hanging wall. Its textures indicate a top-to-the-southeast displacement. The footwall basement consist of the Variscan Morbegno Gneiss and two granitoid intrusions, the Val Biandino Quarz Diorite (VBQD) and the Valle Biagio Granite (VBG). The former is syntectonic with respect to the detachment, whereas for the latter, the relation to the detachment is unknown. Volcanic rocks of the Collio Formation in the hanging wall may represent the extrusive part of the magmatic system. In the study area in the western part of the Orobic anticline, several faults and shear zones are exposed: (1) The top-SE Grassi Detachment Fault. It is truncated by the unconformably overlying, post-rift, Late Permian Verrucano Lombardo towards the NW. This reflects the eroded culmination of a Permian metamorphic core complex. (2) The Sasso Rosso Fault, a steeply NW-dipping, brittle normal in the footwall between VBQD and VBG. It is also sealed by the basal unconformity of the Verrucano Lombardo. (3) Several minor south-directed Alpine thrusts, duplicating the lithostratigraphy, including the detachment. (4) The Biandino Fault, a steeply SE-dipping Alpine backthrust, overprinting the detachment as well as the Alpine forethrusts. U-Pb zircon geochronology using LA-ICP-MS yielded concordant ages of 293.2 ± 4.9 Ma for the VBQD and 286.0 ± 4.8 Ma for the VBG. These ages coincide with the beginning of the Collio volcanism and with the emplacement of mafic melts in the lower crust of the Ivrea Zone, indicating that the volcanics, granitoids and mafic intrusions belonged to a crustal-scale magmatic system. Since structural relations indicate contemporaneity of VBQD intrusion and extensional detachment faulting, it results that the Early Permian magmatism occurred in a framework of core-complex style extension.

Description: The scientific objectives of METEOR cruise M84/5 focused on the measurement and analysis of the environmental controls of modern and fossil cold-water coral growth along a transect in the Bay of Biscay. In four working areas we successfully deployed lander systems and CTD/Ro’s to document the physical and hydrochemical characteristics of bottom water masses and the water column in general. These are used to shed light on potential linkages to modern cold-water coral growth and distribution. These investigations were flanked by plankton tows in surface waters. The base for all investigations was a thorough hydroacoustic survey to characterize potential cold-water coral bearing areas with living colonies. Based on these maps we deployed all video-guided gear such as the OFOS-video sled, the TV grab, and the lander systems. Benthic assemblages and sedimentary structures have been documented and sampled with the OFOS and a box corer. Simultaneously, genetic samples of the living coral material were taken for additional studies. Furthermore, we have taken gravity cores to investigate the paleoceanographic conditions as well as the timing of cold-water coral colonization in the Bay of Biscay. Along with the coring efforts, a detailed sampling and study of porewater properties was performed. An additional aim of this cruise was to investigate the influence of boundary exchange processes on the Neodymium isotopy in bottom waters along the pathway of the Mediterranean Outflow water (MOW) by taking multiple samples with the CTD/Ro. The new data and samples of this METEOR cruise will provide the framework to investigate the timing of cold-water coral colonization in the Bay of Biscay, as well as its interplay with the ambient hydrography and geochemistry. This successful cruise has provided the basis to investigate the scientific aims of this expedition in great detail.