DEVELOPMENT OF THE STRATIGRAPHY OF THE BAHAMIAN ISLANDS (Invited Presentation)

Among the earliest geological work conducted in the Bahamas was that of Captain Nelson who was assigned to duty in Bermuda (1827-1833) and subsequently the Bahamas. His report on the geology of the Bahamas, read by Sir Charles Lyell at the Geological Society of London in 1853, noted that the geology of both places comprised mostly eolian deposits. Although there was much early discussion of apparent relative changes in sea level suggested by the paleosols evident in the rocks of the Bahamas, it seems that Field et al. (1931) were the first to suggest that the geology of Bahamian islands was related to the varying sea levels associated with Pleistocene-Holocene glaciation and deglaciation. Subsequent interpretation of Bahamian geology was generally considered to be the result of deposition of most of the material during the latter stages of the interglacials as sea level was falling, as had been suggested for Bermuda by Sayles (1931). However, as a result of work on San Salvador Island in the mid 1980s it was demonstrated that significant eolian deposits in the Bahamas were emplaced during the early stages of the interglacials as sea level was rising onto the banktops.

Until the 1980s most of the active geological work in the Bahamas was focused on the modern subtidal facies, and the core-based investigation of the geologic history of the Bahama Banks. The researchers investigating bank development referred the surficial rocks of the Bahamas to the Lucayan Limestone, which was correlated to the Miami Oölite in Florida. However, researchers investigating Bahamian geology on San Salvador Island began to develop a stratigraphy that recognized the complexity of depositional units within the “Lucayan Limestone”. In the 1980s a field-based stratigraphy was first proposed for San Salvador Island, and soon those stratigraphic units were shown to be applicable throughout the Bahamas. More recently, refinements to that stratigraphy have been made based primarily on work conducted on Eleuthera and Mayaguana islands. The exciting recent work on Mayaguana has extended the stratigraphy of Bahamian islands back to the Mio-Pliocene. Further refinements to the stratigraphy of the Bahamian islands may await discovery on some, as yet un- or under-explored island, but the likelihood is declining, as there are only a few such places left in the Bahamas.