Abstract
A widespread high-amplitude reflection seen on seismic data throughout the Gulf of Mexico has been called the 'Mid-Cretaceous Unconformity' (MCU). This reflector seems to be a major stratigraphic boundary in the Gulf of Mexico basin. It is believed to correspond to Vail's type 1 unconformity of mid-Cenomanian age (94 Ma), which records an eustatic drop in sea level of approximately 60-100 m. The study area includes all of the Gulf of Mexico with the exception of areas of thick and highly deformed salt, where following the MCU with any degree of confidence becomes impossible.The MCU is easy to follow in multichannel seismic reflection profiles collected in the Gulf of Mexico by the Institute for Geophysics of the University of Texas at Austin. In the central, deeper part of the gulf, reflectors above and below the MCU are parallel. In the southern and eastern rims of the Gulf, along the Campeche and Florida escarpments, reflectors are truncated below the MCU and show onlap relationships above it. The MCU, therefore, may be interpreted as representing an unconformity along the southern and eastern rims of the Gulf of Mexico basin. The unconformity appears to die out and grade into a conformable section toward the central part of the basin. Channeling is common in the MCU along the Campeche and Florida escarpments, which was probably initiated by subaerial exposure of the top of the escarpments during the mid-Cretaceous lowstand. The downslope channels were cut in deep water.
