The foreland consists of the Tertiary Molasse and its Mesozoic substratum. 38 oil and gas fields have beeen found with reserves of l4 million bbl (2 million MT) of oil and 140 bcf (4 billion m 3 ) of natural gas. The fields are associated predominantly with antithetic normal faults and, to a lesser extent, with low-relief anticlines. The lower part of the Molasse and its Mesozoic substratum dip to the south under the Alpine thrust units. Despite its depth of 7,000 m (23,000 ft) and more, the subthrust is still considered to be within the oil window, and is the prime target for exploration in the Bavarian Alps. Seismic exploration in the Alps is difficult because of the rough topography, thick Quaternary sediments, a deep weathering zone, and heterogeneous seismic velocities in the thrust units and their Quaternary cover.--Modified journal abstract.