STRUCTURE, STRATIGRAPHY, AND PETROLEUM GEOLOGY OF THE LITTLE PLAIN BASIN, NORTHWESTERN HUNGARY

The basement of the Little Plain (Kisalfold) basin is composed of two parts: an eastern part comprised of folded and overthrusted Triassic a nd Paleozoic rocks of the Pelso block (Transdanubian Central Range) co mpressed in the Early Cretaceous, and a western part consisting of sta cked nappes of the Austroalpine zone of Paleozoic rocks, significantly metamorphosed during Cretaceous and later compression, overriding Jur assic oceanic rift-zone rocks of the Penninic zone, The evolution of t he basin began in the late Karpatian-early Badenian (middle Miocene) w hen the eastern part of the basin began to open along conjugate sets o f northeast- and northwest-trending normal faults. Neogene rocks in th e study area, on the average, contain less than 0.5 wt, % total organi c carbon (TOC) and, therefore, are not considered effective source roc ks. Locally, however, where TOC values are as high as 3 wt, %, signifi cant amounts of gas may have been generated and expelled, Although pot ential stratigraphic traps are numerous in the Neogene section, these potential traps must be downgraded because of the small amount of hydr ocarbons discovered in structural traps to date. With the exception of the Cretaceous, the Mesozoic section has not been actively explored. Large anticlinal and overthrust structures involving pre-Cretaceous st rata remain undrilled.