The apparent paradox of abundant foramol facies in low latitudes: their environmental significance and effect on platform development

Limited light in moderate to deeper depths of the photic zone, often in regions with a reduced depth euphotic (high light) zone is seen as key to the extensive development of these deposits and the resultant platforms. These conditions are often developed in humid low-latitude areas of high terrestrial runoff (and therefore regions of reduced water salinity), or in areas of nutrient upwelling. Reduced water clarity due to nutrients, plankton blooms, suspended particulate matter, upwelling and strong currents all promote the development of oligophotic conditions and facies on a regional scale. Time periods of relative rises in sealevel can also promote oligophotic facies development. The findings of this study have broader implications for the development of low-latitude platforms beyond Australasia, and during time periods when non-framework building, oligophotic biota are dominant sediment contributors. The reconstruction of past climatic conditions based on study of foramol grain assemblages requires careful study to distinguish warm water deposits from those formed in cool waters.