Interpretation and chronostratigraphic mapping of multichannel seismic reflection profile 195167, Eastern Falkland Plateau (South Atlantic)

摘要

The Falkland Plateau (FP) is a submarine high representing the eastern prolongation of the South America continent. It separates the Argentine Basin of the South Atlantic Ocean from the Scotia Sea of the Antarctic region. A south-north seismic section across the Falkland Plateau has been interpreted using information from two wells sited on the margin of the Maurice Ewing Bank (MEB). On the Plateau, the sedimentary cover has a regionally horizontal configuration with high lateral continuity of the reflecting horizons. The older sequence is dominated by a normal fault system of the Mesozoic Gondwana break-up tectonics, partially reactivated by the following tectonic events. Between them, the one mainly affecting the studied area is the transpression of the North Scotia Ridge (NSR), producing some thrusting in the sedimentary cover of the Falkland Trough (FT, visible only on the south-extremity of the interpreted section) and a prominent tilting of its whole crust. The interpreted seismic section outlines a gradually thinner crust from the Maurice Ewing Bank Margin to the Falkland Plateau and to the Falkland Trough. During the interpretation, particular attention was given to picking the main unconformities, to analysing the relationships of reflections within the sequences to the unit boundaries, and to identifying, by the seismic fades analysis, the different depositional units. These last, labelled with symbols A?G, from Mesozoic to Present age, represent the whole sedimentary cover lying on the pre-Cambrian basement of the Falkland Plateau. In the reconstructed chronostratigraphic section, the whole data set has been displayed as a diagram wherein age decreases upward and the lateral extent of units is on the horizontal scale, illustrating the main sedimentary and erosional events in the area. Erosion, nondeposition and deposition of sediment drifts by the sea bottom currents, particularly active from the Cainozoic to the Present, are mostly linked to the Gondwana breakup, with the Mesozoic opening of the South Atlantic Ocean and the Cainozoic opening of the Drake Passage. During the Mesozoic time, the Proto-South Atlantic and Indian Oceans connection caused extensive erosion and nondeposition, resulting in absence of important portions of the sedimentary cover.