Sediments of the Dry Tortugas, south Florida, USA: Facies distribution on a ramp-like isolated carbonate platform

Satellite‐ and field‐based facies mapping of isolated carbonate platforms from the Kepulauan Seribu Complex, Indonesia

“…Recent studies on carbonate sediment, especially in shallow water, have focused on whether facies distribution is related to bathymetry, questioning the long‐held concept in carbonate geology that changes in water depth can be recognized through analysis of the lithofacies (Bosence, ; Gischler et al., ; Purkis et al., ; Rankey, , ; Wilkinson, Diedrich, & Drummond, ). These authors briefly outline that the understanding of where and how carbonate sediments are produced and accumulated has evolved from the rather simple concept of direct productivity–depth relationships to the recognition that carbonate depositional environments are influenced to some degree by depth, and also by a complex suite of autogenic factors that lead to facies mosaics especially in shallow waters where sediments migrate and superimpose on each other over short distances as a result of subtle environmental changes.…”

“…Purkis et al. () showed that observations on the relationship between facies and water depth can be subdivided into three groups: indistinguishable from random (Purkis & Riegl, ; Purkis et al., ; Rankey, ; Wilkinson et al., ), deterministic order with respect to depth (Bosence, ; Maloof & Grotzinger, ) and incorporating aspects of both random and deterministic (Gischler et al., ; Purkis & Vlaswinkel, ). Study area scale and sampling density emerged to be a significant factor as well because large‐scale studies usually show a distinct relationship between facies and water depth, whereas smaller areas and depth range do not seem to represent a clear cut relationship (Harris, Purkis, & Ellis, ; Purkis et al., ; Rankey, ) and high‐resolution sediment maps are commonly more heterogeneous with facies mosaics instead of broad, homogenous facies belts (Kaczmarek et al., ; Purkis, Harris, & Ellis, ).…”

“…Correlation, cluster and principle component analysis were conducted using the software package PAST (Hammer, Harper, & Ryan, 2001). Sediment samples were classified using a modified Dunham (1962) classification following the method outlined in Gischler et al (2017) which proposed a threshold value of 50% matrix to separate mud supported from grain-supported textures. Grainstone has 0%-10%, packstone 10%-50%, wackestone 50%-90% and mudstone 90%-100% matrix.…”

“…The small, isolated carbonate platforms forming the islands of the Kepulauan Seribu Complex therefore provide a useful modern analogue for buried carbonate systems in Indonesia (Park et al., ; Wilson, ) and other similar Cenozoic carbonates from Southeast Asia and northern Australia (Belde, Back, Bourget, & Reuning, ; Morgan, George, Harris, Kupecz, & Sarg, ; Rosleff‐Soerensen, Reuning, Back, & Kukla, , ). Sediment distribution patterns form the fundamental studies on sediment formation, redeposition, sediment dynamics and early diagenesis in modern reefs and carbonate platforms (Gischler, ; Gischler, Isaack, & Hudson, ).…”

Hardened faecal pellets as a significant component in deep water, subtropical marine environments

“…The abundance of pellets in these relatively deep‐water temperate carbonates is therefore similar or higher than most tropical carbonate shoals and shallow water platforms in the Indo‐Pacific region (Gischler, ; Utami, Reuning, & Cayharinin, ). Many carbonate platforms and shoals in the Caribbean (Milliman, , ) have higher peloid contents compared to IODP site U1460, but several have similar or even lower peloid abundances, for example the Dry Tortugas shoal on the distally steepend ramp of the west Florida shelf or the Turneffe Islands platform off Belize (Gischler, Isaack, & Hudson, ; Gischler & Zingeler, ). The skeletal assemblage contained in those shallow water, tropical faecal pellets is partially similar to the pellets from deeper water, temperate carbonates described in this study.…”