An Amphibious Seismic Study of the Crustal Structure of the Adriatic Microplate

The present-day structure of the southern Adriatic area is controlled by two oppositely-vergent fold-and-thrust belt systems (Apennines and Dinarides). The Adriatic continental domain is one of the most enigmatic segments of the Alpine-Mediterranean collision zone. It separated from the African plate during the Mesozoic extensional phase that led to the opening of the Ionian Sea. Basin widening and deepening peaked during Late Triassic-Liassic extension, resulting in the formation of the southern Adriatic basin, bounded on either side by the Dinaric and Apulian shallow water carbonate platforms. Because of its present foreland position with respect to the Dinaric part of orogenic belt, the southern Adriatic basin represents the only remnant of the Neotethyan margin and offers the unique opportunity to image a segment of Mesozoic passive margin in the Mediterranean. To study the deep crustal structure, the upper mantle and the shape of the plate margin, the German research vessel Meteor acquired 2D seismic refraction and wide-angle reflection data during an onshore-offshore experiment (cruise M86-3). We present two profiles: Profile P03 crossed Adria from the Gargano Promontory into Albania. A second profile (P01) was shot parallel to the coastlines, extending from the southern Adriatic basin to a possible mid-Adriatic strike-slip fault that purportedly segments the Adriatic microplate. Two different approaches of travel time tomography are applied to the data set: A non-linear approach is used for the shorter profile P01. A linear approach is applied to profile P03 (360 km length) and allows for the integration of the 36 ocean bottom stations and 19 land stations. First results show a good resolution of the sedimentary part of the Adriatic region. The depth of the basement as well as the depth of the Moho discontinuity vary laterally and deepen towards the North-East, consistent with the notion of flexural loading of the externally propagating orogenic wedge of the Dinarides.