4D geologic evolution in the Gaeta Bay sedimentary infill (Eastern Tyrrhenian Sea)

The Gaeta Bay in the Eastern Tyrrhenian Sea is characterized by faulted bounded basins formed in association with the back-arc extension. The present study, based on multichannel seismic reflection profiles, focuses on the seismic stratigraphy of the sedimentary succession of this region. Using the Kingdom® software (copyright IHS) we constructed a digital model of the Gaeta Bay infill that permits to recognize the 3D architecture of the depositional sequences. We recognize two (northern and central) sub-basins bounded by normal faults and characterized by high rates of subsidence. The complete stratigraphic succession occurs in the northern part of the Gaeta Bay. The sedimentary infill overlies the Mesozoic-Cenozoic substrate; it is formed by two unconformity-bounded units overlain by thirteen sequences grouped into three sequence sets (A-C). The basal unconformity-bounded units are wedge-shaped and were deposited during fault activity and basin formation. Sequence set A is characterized by parallel reflectors, the seismic facies of which suggest a regressive trend. Sequence set B is characterized by prograding depositional units with an aggradation of the toplap surface suggesting a new period of rift basin subsidence. Sequence set C is instead characterized by oblique prograding depositional units that indicate a post rift infill of the northern part of the Gaeta Bay. The analysis of the resulting 2D and 3D distribution of the depositional units allows revealing the architectural interpretation of the stratigraphic basin infill. The four-dimensional Quaternary paleogeographic evolution of Gaeta Bay is finally reconstructed.