The Belize margin revisited: 1. Holocene marine facies

Abstract

Belize is best known for its 260-km-long barrier reef and associated lagoon reef shoals, but also exhibits a complete transition from near-shore siliciclastics to pure carbonate deposits across a narrow shelf lagoon and, in addition, has three of the very few occurrences of Caribbean atolls. Published Holocene facies relationships on the Belize shelf have been semiquantitative in that they are based on quantitative point count thin section data in the northern shelf lagoon and on qualitative estimates of thin section composition in the southern shelf lagoon. This contrast has been rectified by point counting southern shelf lagoon thin sections and incorporating the result with published point count data from the northern shelf, supplemented by additional information, to produce a modified factor analysis facies distribution for the entire shelf. The resulting nine facies are extended seaward to include previously published analysis of sediment on the three Belize off-shelf atolls, resulting in a total of 11 facies. In addition, the carbonate mud distribution has been mapped over both the shelf and atolls with the not unexpected result that, in places, the distribution pattern clearly indicates a barrier platform source of lagoon-deposited carbonate mud. Dunham's limestone classification terminology has been used as a basis for description to make these relationships more useful to those reconstructing ancient limestone depositional environments.

New perspectives on ecological mechanisms affecting coral recruitment on reefs

“…Mangrove communities were established at Twin Cays about 8,000 years ago on the Pleistocene surface of the Belize Barrier Reef Platform when it was fl ooded during the Holocene Transgression (Macintyre et al, 2004b;Purdy and Gischler, 2003). Deep deposits of peat (as much as 11 m thick) have developed as Twin Cays accreted vertically with rising sea level (Macintyre et al, 2004b;McKee et al, 2007a).…”

“…Twin Cays and the Pelican Cays ranges have been a major focus of mangrove research by the Smithsonian Institution Macintyre et al, 2004a). These mangrove islands are far from the mainland, and peat cores contain no terrigenous sediment (Cameron and Palmer, 1995;McKee and Faulkner, 2000;Purdy and Gischler, 2003;Macintyre et al, 2004b). The only source of freshwater is rainfall, and the entire landform is intertidal (mean tide range [neap] ϭ 0.2 m).…”

Fish as major carbonate mud producers and missing components of the tropical carbonate factory

“…Ultimately variable admixtures of both aragonite and Mg-calcite mud-grade carbonate occur and thus budgetary considerations need to accommodate production from a range of potential sources. This issue has important geo-environmental implications because carbonate muds are major constituents of limestones and are volumetrically important in most modern shallow marine carbonate environments (17). Furthermore, the presence of Mg-calcite muds in marine carbonates is considered critical to preserving primary sediment textures and fabrics (15), thus influencing sediment porosity and permeability which are of critical importance to fluid flow in limestone sequences.…”

Whiting-related sediment export along the Middle Miocene carbonate ramp of Great Bahama Bank

“…In addition, whitings have also been observed on modern ramp settings such as the shelves of Yucatan (Belize) or the shallow region of the Persian Gulf. The sedimentary significance of whitings observed in the southwest of Cay Corker in Belize is unknown, although the water column is supersaturated with respect to aragonite (Purdy and Gischler 2003). In the Persian Gulf, Wells and Illing (1964) have shown that whiting formation, most frequent in its southern part, is not accompanied by salinity or temperature variations or by changes in seawater pH.…”

“…Whitings are milky patches of suspended material with dimensions varying between several hundred metres to several kilometres in diameter and are mainly known from tropical and subtropical settings (Bahamas : Cloud 1962a, b;Broecker and Takahashi 1966;Shinn et al 1989-Persian Gulf: Wells andIlling 1964;De Groot 1965-Dead Sea: Neev and Emery 1967-Belize: Mazzulo et al 1995Purdy and Gischler 2003). Whitings have also been described from lake environments (Great Lakes: Strong and Eadie 1978-Otisco Lake: Effler and Johnson 1987-Fayetteville Green Lake: Thompson and Ferris 1990;Thompson et al 1997;Thompson 2000-Croatian marine lake: Sondi and Juračič 2010).…”