Correlation of Seismo- and Magnetostratigraphy in Southeastern Hungary

Abstract

Correlation of results from magnetostratigraphic and seismic-reflection studies indicate that the Pannonian Basin, during the postrift phase of its evolution (middle Miocene to present), became filled by sediments of southward and eastward prograding deltaic wedges.

In the Békés basin (a subbasin of the Pannonian Basin), the Badenian-Sarmatian age (16.5 to12 Ma) section, where explored by drilling, is relatively thin (generally less than 275 m) and represents principally shallow-water, nearshore, marine-brackish water environments. During latest Sarmatian and early Pannonian time (12−9 Ma), the Békés basin was starved, as other subbasins located along its margins captured most of the sediment load carried by rivers. During this time interval, a combination of relatively low deposition rates and high subsidence rates produced great water depths (about 900 m) in the Békés basin. By middle Pannonian time (6–7 Ma), subbasins on the margins of the basin had become filled with sediments as deltas gradually prograded across them. As a result of this filling process, a platform was constructed across which rivers transported their sediment loads into the Békés basin. Thereafter, deltaic filling of the basin proceeded rapidly and rates of sediment accumulation reached 1000 m/million years. Lacustrine sediments, more than 6000 m thick, were deposited in the deeper parts of the basin.

Indirect evidence suggests that lake levels in the Pannonian inland sea (a remnant of the Paratethys), although isolated from the world’s oceans, were affected by eustatic sea level changes. Three hiatuses were identified on seismic profiles from the northern margin of the Pannonian Basin, and are inferred to represent non-deposition. These hiatuses (7.9−7.6, 6.8−5.7, and 5.4−4.6 Ma) appear to correlate with global eustatic sea level minima. This suggests that the Pannonian inland sea became gradually isolated from the world oceans, and fluctuated in phase with global sea level. The hiatus between 6.8 and 5.7 Ma is tentatively correlated with the Messinian global stage, during which time evaporite deposition in the Mediterranean was widespread — the so-called “Messinian salinity crisis ” (Hsü and others, 1973).