ALBERT

Description: Analysis of structural and sedimentologic data from onshore outcrops, offshore wells, and offshore seismic profiles indicates that the thrust belt geometry in eastern Bulgaria from the Paleocene to the Holocene is characterized by a southeastward plunge toward the western Black Sea Basin. This plunge was caused by (1) a combination of eastward-thinning continental crust in the west and oceanic crust in the east; (2) a postrift thermal subsidence of the continental crust; (3) buttressing and no buttressing of the Moesian platform against the thrust belt in its western and eastern parts, respectively; and (4) northeastward thrust belt advance. These factors controlled the overall eastward-diminishing uplift of the thrust belt and associated eastward sediment funneling into the Black Sea. Evidence for the eastward-fading uplift and buttressing includes the (1) eastward decreasing amount of shortening along constructed cross sections, yielding 30, 10.5, 11, and 4 km (18.6, 6.5, 6.8, and 2.5 mi, respectively) from west to east, respectively; (2) eastward trend of more complete stratigraphic sections and shallower erosional levels; and (3) eastward increase in decollement depths, being 3.7, 3.8, 9.5 to 13.5, and 12.3 to 14.1 km (2.3, 2.4, 5.9-8.4, and 7.6-8.8 mi). The age of the last thrusting is progressively younger toward the east from the middle Eocene through the late Eocene to the Oligocene from west to east, respectively. Onshore parts of the thrust belt, which were significantly affected by buttressing against the Moesian platform, exhibit thrusting followed by late Eocene gravitational collapse, Oligocene quiescence, and Neogene extension. The thrust belt part farther east exhibits thrusting followed by Oligocene-Neogene extension. A Paleocene-middle Eocene piggyback basin formed in the onshore part of the thrust belt, centered in the East Balkan zone, with a southeastward-plunging axis, which migrated northeastward with basin shortening and filling. The development of the East Balkan thrust belt and its later extensional modification had a dominant control over sediment transport, lithofacies, and depositional patterns. Developing thrust belt fold 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, together with subordinate internal synclinal axes. These depressions funneled sediments toward and into the western Black Sea Basin. As orogenesis advanced to the northeast, former depositional areas were uplifted and eroded, providing local sources of sediment.

Description: Analysis of structural and sedimentologic data from onshore outcrops, offshore wells, and offshore seismic profiles indicates that the thrust belt geometry in eastern Bulgaria from the Paleocene to the Holocene is characterized by a southeastward plunge toward the western Black Sea Basin. This plunge was caused by (1) a combination of eastward-thinning continental crust in the west and oceanic crust in the east; (2) a postrift thermal subsidence of the continental crust; (3) buttressing and no buttressing of the Moesian platform against the thrust belt in its western and eastern parts, respectively; and (4) northeastward thrust belt advance. These factors controlled the overall eastward-diminishing uplift of the thrust belt and associated eastward sediment funneling into the Black Sea. Evidence for the eastward-fading uplift and buttressing includes the (1) eastward decreasing amount of shortening along constructed cross sections, yielding 30, 10.5, 11, and 4 km (18.6, 6.5, 6.8, and 2.5 mi, respectively) from west to east, respectively; (2) eastward trend of more complete stratigraphic sections and shallower erosional levels; and (3) eastward increase in decollement depths, being 3.7, 3.8, 9.5 to 13.5, and 12.3 to 14.1 km (2.3, 2.4, 5.9–8.4, and 7.6–8.8 mi). The age of the last thrusting is progressively younger toward the east from the middle Eocene through the late Eocene to the Oligocene from west to east, respectively. Onshore parts of the thrust belt, which were significantly affected by buttressing against the Moesian platform, exhibit thrusting followed by late Eocene gravitational collapse, Oligocene quiescence, and Neogene extension. The thrust belt part farther east exhibits thrusting followed by Oligocene–Neogene extension. A Paleocene–middle Eocene piggyback basin formed in the onshore part of the thrust belt, centered in the East Balkan zone, with a southeastward-plunging axis, which migrated northeastward with basin shortening and filling. The development of the East Balkan thrust belt and its later extensional modification had a dominant control over sediment transport, lithofacies, and depositional patterns. Developing thrust belt fold 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, together with subordinate internal synclinal axes. These depressions funneled sediments toward and into the western Black Sea Basin. As orogenesis advanced to the northeast, former depositional areas were uplifted and eroded, providing local sources of sediment. Charles J. Stuart retired from Unocal Corporation in 2000 and Energy and Geological Science Institute in 2009. He received his Ph.D. in clastic sedimentology and stratigraphy at the University of California, Santa Barbara in 1975, his M.S. degree in geology at the University of Montana in 1966, and his B.S. degree in geology from San Diego State University in 1964. His principal work has been in seismic and sequence stratigraphy and deep-water clastic facies, with emphasis on depositional systems, basin evolution, and reservoir interpretation at both basinwide and prospect scales. More recent work areas include Indonesia, Malaysia, India, and west Africa, as well as the Black Sea Basin. Michal Nemčok holds the research professorship in the Energy and Geoscience Institute and adjunct professorship in the Department of Geology and Geophysics at the University of Utah. He received his Ph.D. in structural geology from Comenius University, Bratislava, Slovakia in 1991. His primary interests are structural interpretation and modeling and their application to thrust belts and passive margins. Dian Vangelov works as an associate professor of regional geology at the Department of Geology, Paleontology, and Fossil Fuels at Sofia University. He received his M.S. degree from Sofia University in 1985. From 1986 to 1992, he worked as research scientist at the Bulgarian Geological Survey. He defended his Ph.D. at Sofia University in 2001. His research focus is on basin analysis. Eric Higgins is employed as an exploration geologist at Chesapeake Energy, focusing on North American new ventures. Before arriving at Chesapeake in 2005, he was involved in a variety of exploration projects in Africa, the Middle East, and Europe, as well as the Jurassic of the U.S. Gulf Coast. Between 2002 and 2005, he was chief geoscientist for Vintage Petroleum's Burgas Deep Sea license in the western Black Sea Basin, offshore Bulgaria. He earned his M.S. degree in geology from the University of Oklahoma in 2000 and holds an M.A. degree in history from the University of Wisconsin awarded in 1993. Chelsea Welker is currently the database manager and Geographic Information System (GIS) analyst for the structural geology group at the Energy and Geoscience Institute at the University of Utah. She received her B.S. degree in geophysics in 2002 and her GIS certificate in 2004, both from the University of Utah, Salt Lake City, Utah. Her areas of interest include geology and petroleum-related questions that can be answered through the use of GIS. David Meaux is currently assigned as an R&D projects manager for BP Imaging Flagship group in Houston, Texas. He received his M.S. degree in geology from the University of Houston in 1989. His current focus is on geophysical imaging technologies development and deployment. David also serves as an adviser on nonseismic geophysics technologies at BP.