A Diverse Patch Reef From Turbid Habitats in the Middle Miocene (East Kalimantan, Indonesia)

Abstract

The Kutai Basin (East Kalimantan, Indonesia) contains a rich and well-preserved Miocene fossil record of small patch reefs that developed under the influence of high siliciclastic input associated with the progradation of the Mahakam Delta. In this study, we reconstruct the biodiversity and paleoenvironments on one of these delta-front, mixed carbonatesiliciclastic systems that developed at the Serravallian-Tortonian boundary near the city of Samarinda. In two newly exposed sections, we analyzed the sedimentology and distribution of the main fossil biota including corals, foraminifers, coralline algae, and bryozoans. Seven facies are herein defined, including two dominated by platy corals and two by larger benthic foraminifera. Facies distributions were driven by changes in depth and variations in terrigenous input within a range of delta-front habitats. Despite the turbid conditions, fossil assemblages are highly diverse, including 69 coral species and 28 bryozoan species that occur in coral-dominated facies. Crustose coralline algae were mainly associated with the coral-dominated facies. Larger benthic foraminifera showed broader ecological tolerance within the range represented in the studied sections and thus are common in most facies. These diverse patch reef ecosystems were able to cope with high siliciclastic input during the early development of the Miocene coral reef biota.

The evolution of fishes and corals on reefs: form, function and interdependence

“…In marked contrast, in Phase 5 we see the origins of the vast majority of reef fish genera but no new families (the origin of the Chaetodontidae in the Oligocene may be the sole exception; Cowman & Bellwood, 2011). In corals, many genera are recorded in the Eocene fossil record (Papazzoni et al, 2014b), but it is not until Phase 5 that we see evidence of extensive diversification within major coral groups (Santodomingo et al, 2015). Phase 5 also marks the appearance of new functional groups associated with high-turnover ecosystem dynamics (Bellwood et al, 2014b) and the invasion of new habitats (Bellwood et al, 2014a).…”

“…However, these new IAA coral formations may not have been as we see them today. Fossil evidence is increasingly pointing to mesophotic corals playing an important role in the early-mid Cenozoic (Wallace & Rosen, 2006;Mihaljević et al, 2014;Johnson et al, 2015;Santodomingo et al, 2015;Wilson, 2015). In most cases, the low light conditions (hence mesophotic) are considered to be a result of turbidity in relatively shallow water rather than as a result of depth.…”

Deep in shadows, deep in time: the oldest mesophotic coral ecosystems from the Devonian of the Holy Cross Mountains (Poland)

“…MCEs are dominated by platy or encrusting corals, and such a morphology is broadly considered as photoadaptive growth (e.g., Macintyre 1976, 1982;Rosen et al 2002;Anthony and Hoegh-Guldberg 2003;Kahng et al 2010Kahng et al , 2012Kahng et al , 2014. Platy morphologies in scleractinians were possibly widespread in Meso-and Cainozoic reefs (Rosen et al 2002), and are indicative of photosymbiosis in fossil record (e.g., Insalaco 1996;Rosen et al 2002;Santodomingo et al 2015). Platy corals were recorded as early as in the Late Triassic (ca.…”

Calcitization of aragonitic bryozoans in Cenozoic tropical carbonates from East Kalimantan, Indonesia

“…Early to middle Miocene deltas prograded rapidly eastwards, contributing to the infilling of the Kutai Basin (Moss and Chambers 1999;Hall and Nichols 2002). Within this depositional regime, Miocene carbonates formed as delta-front reefs (Wilson 2005;Santodomingo et al 2015), shelf-edge reefs Novak et al 2013;Novak and Renema 2015), and small carbonate platforms (Wilson et al 2012), along the seaward margin of the Mahakam Delta where they were strongly influenced by siliciclastic input throughout their evolution (Wilson 2005;Lokier et al 2009;Marshall et al 2015). These carbonates have been interpreted as transitional shelf sediments deposited between deltaic and deepmarine facies (Allen and Chambers 1998).…”

“…Bryozoans are restricted, in both sections, to the coral sheetstone facies characterized by dominant thin-platy corals and occasional branching coral fragments, forming a sheetstone fabric in a muddy matrix, with subordinate larger benthic foraminifera, calcareous algae in low proportion, sparse cidaroid echinoid spines and fragments of calcitic gastropods and bivalves Santodomingo et al 2015).…”