ALBERT

Description: The unconsolidated sedimentary layer in the eastern Mediterranean Sea becomes more variable in thickness toward the east. The distribution pattern suggests that the primary sources of sediment in Cenozoic times have been the Nile River, elevated areas of Cyrenaica, the Taurus, and the Apennines.

Description: Submitted to the Office of Naval Research under contract Nonr-4029 (00); NR 260-101, and partially supported by National Science Foundation Grants GP-2370 and GA-283.

Description: In March 1971, seven members of the Woods Hole Oceanographic Institution were engaged in a multidisciplinary study of Lake Kivu. This expedition represents part of a long-range program concerned with the structural and hydrographical settings of the East African Rift Lakes and their relationships to the Red Sea and the Gulf of Aden Rifts. The program started in May 1963 with a geophysical study on Lake Malawi (von Herzen and Vacquier, 1967). Several expeditions of our Institution into the Red Sea and Gulf of Aden area in 1964, 1965 and 1966 (Degens and Ross, 1969) provided detailed geological information on the "northern" extension of the East African Rift. And finally our study of last year on Lake Tanganyika c1osed a major gap in the program; it allowed us to out1ine a model on the evolution of a rift which starts with (i) bulging of the earth's crust, (ii) block-faulting, (iii) volcanism and hydrothermal activity, and which has its final stage in (iv) sea floor spreading (Degens et al. 1971). In the case of Lake Tanganyika, only the second stage of this evolution series has been reached, i.e. block-faulting. In contrast, the Red Sea and the Gulf of Aden had already evolved to active sea floor spreading, almost 25 million years ago. Somewhere along the line between Lake Tanganyika and the Gulf of Aden must lie the "missing link" of this evolution series. Lake Kivu, almost 100 miles to the north of Lake Tanganyika is situated at the highest point of the Rift Valley and is surrounded by active volcanoes and geothermal springs. As recently as 1944, lava flows reached the lake shore. This lake was therefore, a natural choice to test our hypothesis on the origin and development of rifts. Furthermore, the occurrence of large quantities of dissolved gases, e.g., CO2 and methane, represented an interesting geochemical phenomenon worthwhile to investigate.

Description: Supported by the National Science Foundation with Grants GA 19262, GB 20956, and GU 3927; grants from the Petroleum Research Fund of the American Chemical Society PRF#1943A2; and by private research funds of the Woods Hole Oceanographic Institution.

Description: The Black Sea is an extensional back-arc basin developed along the northern active margin of the Tethys Ocean which was subducted northward from the Triassic to Miocene times. The Romanian Black Sea shelf is dominated by mid-Cretaceous extensional structures and their sedimentary cover, subsequently affected by Cenozoic compression. Here we analyse the post-Oligocene structural and sedimentological evolution of the shelf, based on Romanian oil industry data consisting of (1) 5300 line-km reflection seismic profiles situated on the shelf and continental slope; and (2) depth and lithostratigraphic information from 60 boreholes on the shelf. Our study provides evidence for a changing evolution of the shelf during a relatively short period of time directly related to the pre-Miocene period and the evolution of the Romanian onshore. Mio-Pleistocene subsidence of the Romanian Black Sea shelf is highly variable and is directly dependent on sediment input, tectonic activity as well as water-level fluctuations. Subsidence during the Badenian-Sarmatian and the Dacian-Quaternary was limited. In contrast, during the Pontian, shelf subsidence was progressively faster in the basinward direction. Subsidence on the outer shelf was much more significant than elsewhere on the shelf. Tectonically, the most active period during the Mio-Pleistocene was the Pontian. The Badenian-Sarmatian was largely quiescent and the Dacian-Quaternary saw a decrease in the Pontian tectonic activity, coming possibly even to a halt. From a sequence-stratigraphical point of view, eight systems tracts were identified for the Mio-Pleistocene sedimentary section. The Badenian-Sarmatian unit was attributed to a HST (highstand systems tract). The Pontian unit was subdivided into P1, P2, P3 and P4. Subunit P1, which was laid down on the slope at the time of deposition, is progradational and attributable to the lowstand wedge of a LST (lowstand systems tract). Subunit P2 is likewise also attributed to a LST, having the continental slope and the deep basin as palaeo-depositional environments. The reflection terminations and the wedge-shape of P3 suggest that it was deposited in the deep basin during a sea level lowstand. The next transgressive systems tract (TST) and HST developed during the deposition of P4. The boundary between P4 and the Dacian is represented by an erosional hiatus, which comprises the LST that follows the formation of the sequence boundary at the end of the Pontian. During the Dacian-Quaternary, the subsequent TST and HST were deposited on the inner and middle shelves. Sedimentation on the Romanian shelf during the Mio-Pleistocene period was thus strongly influenced by sediment input and subsidence, while sea level fluctuations played a lesser role. As sediment input is related to the evolution of the adjacent land and subsidence is dependent on sediment supply, tectonic activity and sea level fluctuations, these two factors are not totally independent.