Effects of Tectonics on Deposition in the Balkans of Eastern Bulgaria

Michal1 Nemcok¹, Charles J. Stuart², Dian Vangelov³, Eric R. Higgins⁴, Chelsea Welker², and David Meaux^5
1Energy and Geoscience Institute, University of Utah, Salt Lake City, UT
²EGI at University of Utah, Salt Lake City, UT
³Department of Geology at Sofia University, Sofia, Bulgaria
⁴Chesapeake Energy Corporation, Oklahoma City, OK
⁵AOA Geophysics Inc, Houston, TX

The E Balkans geometry during Paleocene-Recent was characterized by a southeastward plunge toward the Western Black Sea, caused by: 1) a combination of eastward-thinning continental crust in the west, and oceanic crust in the east; 2) post-rift thermal subsidence of the continental crust; 3) buttressing against the Moesian Platform in the west and no buttressing in the east; and 4) northeastward advance of the thrustbelt.
The eastward-fading uplift and buttressing are evidenced by: 1) eastward decreasing amount of shortening along constructed profiles, yielding 30km, 10.5km, 11km and 4km from west to east; 2) eastward trend of more complete stratigraphic sections and shallower erosional levels; and 3) eastward increase in décollement depths, being 3.7km, 3.8km, 9.5-13.5km and 12.3-14.1km. The last thrusting age is progressively older toward the east from Middle Eocene through Late Eocene to Late Eocene/Oligocene. Onshore thrustbelt, which was significantly affected by buttressing against the Moesian Platform, exhibits thrusting followed by Late Eocene gravitational collapse, Oligocene quiescence and Neogene extension. The offshore thrustbelt exhibits thrusting followed by Oligocene-Neogene extension. A Paleocene-Middle Eocene piggyback basin formed in the onshore portion of the thrustbelt, centered in the East Balkan Zone, with a southeastward plunging axis, which migrated northeastward with basin shortening and filling.
Developing thrustbelt structures, together with the orogenic hinterland and highs in the foreland, formed a northeastward and eastward expanding system of sediment input. Southeastward plunging axes of the foreland basin and the Paleocene-Middle Eocene piggyback basin were the principal sediment transport pathways into the Western Black Sea basin.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece