Sea Level Events and Pleistocene Coral Ages in the Northern Bahamas

Abstract

Emergent Pleistocene sea level indicators in the northern Bahamas include: a bioerosional notch at +5.3 to 5.9 m; sea caves, notches, and marine terraces at about +4.3 m; and lithified coral rubble and reef deposits between 0 and 3 m. Thorium 230 dates of the fossil corals, which were deposited as these features were being produced, span the age range from 100 to 145 thousand years BP with a majority falling between 115 and 130 thousand years BP. The notch at about +5.6 m is interpreted to be the product of a sea level stand 125 thousand years BP, while the features at +4.3 m are believed to be formed sometime later as sea level fell from the higher position. Part of the age span is inherent in the dating technique and possible sample alteration. Another cause of the spread may be mixing of corals of different ages into a single deposit.

Speleothems in a wave-cut notch, Cayman Brac, British West Indies: The integrated product of subaerial precipitation, dissolution, and microbes

“…Notches at similar elevations on other Caribbean islands have also been attributed to this highstand (Neumann and Moore, 1975).…”

Pleistocene facies of Belize barrier and atoll reefs

“…Reconstructions of sea-level variation based on Pleistocene reef data were made in various locations including the Huon Peninsula, New Guinea (Chappell 1974), the Bahamas (e.g., Neumann and Moore 1975), Bermuda (e.g., Vacher and Hearty 1989), Barbados (e.g., Bard et al 1990), the Cook Islands (Gray et al 1992), Mururoa (Camoin et al 2001) and Mayotte (Zinke et al 2003). Numerous studies identified marine isotope stage (MIS) 5e reefs, which form either prominent terraces or the foundations of modern reefs (Thurber et al 1965, Eniwetok;Dodge et al 1983, Haiti;Woodroffe et al 1983, Cayman Islands;Marshall and Davies 1984, Great Barrier Reef;Battistini et al 1986, Guadeloupe;Zhu et al 1993, Abrolhos;Szabo et al 1994, Hawaii;Israelson and Wohlfarth 1999, the Seychelles;Fruijtier et al 2000, south Florida).…”

Last interglacial (MIS 5e) sea-level determined from a tectonically stable, far-field location, Eyre Peninsula, southern Australia

“…A de facto estimate of eustatic sea level for MIS 5e of 6 m above present sea level (APSL) was inferred from early compilations of relative sea level observations for the Pacific and Indian Oceans, which showed fossil corals between 2 and 9 m APSL in settings remote from active plate boundaries (Veeh 1966;Murray-Wallace & Belperio 1991). Subsequent work in the northern Bahamas (Grand Bahamas and Abaco) identified prominent shoreline notches at 5.9 m APSL and U-series ages with a mean age of 125 ka (Neumann & Moore 1975) seemed to corroborate the 6 m APSL inferred eustatic sea level for MIS 5e. On this basis, subsequent investigations have used the 6 m value as a datum for quantifying rates of tectonic uplift in plate boundary settings (Broecker et al 1968;Chappell 1974;Bloom et al 1974 and many others since) for inferring the ages of older or younger reef terraces.…”