Paleotempestite Distribution across an Isolated Carbonate Platform, San Salvador Island, Bahamas

Abstract

Mattheus, C.R. and Fowler, J.K., 2015. Paleotempestite distribution across an isolated carbonate platform, San Salvador Island, Bahamas. Journal of Coastal Research, 31(4), 842-858. Coconut Creek (Florida), ISSN 0749-0208. Sediment cores were collected from coastal ponds across San Salvador Island, an isolated Bahamian carbonate platform, and integrated with aerial photographs and field-survey data to provide insight into how spatially variable storm records are at the island scale and what drives this variance. A better understanding of local tempestite generation and preservation potential is crucial for correlating events across more regional scales. Sandy storm layers, products of beach overwash and/or high-energy aeolian transport from the shore into coastal ponds, are easily distinguished from flocculated carbonate muds, microbial mats, and other organics that ordinarily sequester in the stagnant, low-energy coastal water bodies. Interpreted paleotempestites do not correlate well between studied ponds using a strictly stratigraphic approach, although all sites investigated are situated within 150 m of a sandy beach, are similar in size and morphology, and coastal terrains across the small island are comparable. While wrack lines show that individual storms produce surges that vary in height along the island's 60 km-long coastline, differences in the spatial distribution of storm deposits cannot be explained solely as a function of variable surge heights, storm trajectories, and shore aspect; they also reflect intrinsic, biogeomorphic variables such as pond-fringing vegetation characteristics and coastal geomorphic configuration. A complete storm chronology for the island is not generated in any single pond location, and diagenetic processes compound this variance, producing a high degree of spatial heterogeneity of storm records. Nonetheless, the Caribbean-wide Hurricane Hyperactivity Period is distinguished in core from the modern period of relative inactivity by an up-core transition from sandy, stratified pond deposits containing storm layers to heavily bioturbated sediments indicative of low-E deposition. This facies transition, recognized across the island, provides a regional correlation tool for evaluating the distribution of paleotempestites within context of major climate regimes. ADDITIONAL INDEX WORDS:Coastal pond, washover fan, carbonate, Hurricane Frances, storm deposit.

High Productivity Makes Mangroves Potentially Important Players in the Tropical Silicon Cycle

“…The lower concentrations of Si in mangroves, compared to higher latitude wetlands and many temperate tree species could be due to several factors. First, DSi availability may be low in Caribbean mangrove systems due to typically low DSi concentrations in tropical marine waters, carbonate platforms, and highly weathered soils (Kaye, 1959;Marfia et al, 2004;Shipe et al, 2006;Gulley et al, 2014;Mattheus and Fowler, 2015). Lower DSi availability in sediments, and therefore sediment porewater, would result in lower Si accumulation as plants passively (i.e., take up Si as they take up water) incorporate Si into their transpiration stream.…”

Upper Pleistocene parabolic ridges (i.e. ‘chevrons’) from the Bahamas: Storm‐wave sediments or aeolian deposits? A quantitative approach

“…Indeed, recent hurricane sediments consist of localized sand sheets, conglomeratic berms and washover fans or lobes ( Fig. 12; Donnelly et al, 2006;Donnelly & Sallenger, 2007;Morton et al, 2007;Williams, 2011;Mattheus & Fowler, 2015) that are several orders of magnitude smaller than 'chevrons' (table 4 in Morton et al, 2007;Jamison-Todd et al, 2020) and never display such a V-shaped morphology (Engel et al, 2015). Finally, sandy storm deposits are systematically thinning landward with slopes ranging from 1°to 5°whereas 'chevrons', like parabolic dunes, are thickening as they progress inland ( Figs 5 and 6) with the highest elevation lying near the ridge apex (Hearty et al, 1998;Hearty & Tormey, 2017;Vimpere et al, 2019).…”

A review of the spatial distribution of and analytical techniques used in paleotempestological studies in the western North Atlantic Basin

“…Some have used a more qualitative approach which includes describing the presence of visible sand layers which are then attributed to past hurricane strikes, often based on a comparison of the timing of these sand layers with historically documented TCs (Donnelly et al, 2001a, 2001b, 2004; Hansom and Hall, 2009; Liu and Fearn, 2000; Liu et al, 2008, 2011; Scott et al, 2003). On a quantitative level, the sieving method, which works to separate particles into size fractions (often greater or less than 63 µm), is widely used (Brandon et al, 2014; Donnelly et al, 2015; Hippensteel and Martin, 1999; Kiage et al, 2011; Lane et al, 2011; Mattheus and Fowler, 2015; McCloskey and Keller, 2009; McCloskey and Liu, 2013; Reese et al, 2008; Williams, 2009, 2010, 2013) and can be an efficient way of determining key grain-size fractions, such as percent sand, in a sample. Laser particle size analyzers (LPSA) are a newer, more costly, yet more precise method for grain-size analysis and their advantage lies in their ability to generate a complete grain size distribution from a small sample in fractions much finer than what is possible with mechanical sieving (Boldt et al, 2010; Brown et al, 2014; Donnelly and Woodruff, 2007; Hawkes and Horton, 2012; Horton et al, 2009; Malaizé et al, 2011; McCloskey and Liu, 2012; Naquin et al, 2014; Nikitina et al, 2014; Peros et al, 2015; Toomey et al, 2013; Van Hengstum et al, 2014).…”