A Late Quaternary record of highstand shedding from an isolated carbonate platform (Juan de Nova, southern Indian Ocean)

Abstract

A 27 m core collected on the sea floor near Juan de Nova island at 1,909 m depth in the SW Indian Ocean preserves a high‐resolution record of carbonate sediment export to the deep sea over the past 1 Myr. Core chronology was established using calcareous nannofossil biostratigraphy and benthic foraminiferal δ18O. Throughout the core, preserved highstand intervals (MIS 1, 5, 7, 9, 11, 13, 15, 23 and 25) are marked by an increase in the aragonite content within the sediment. Aragonite is likely sourced from the nearby Juan de Nova carbonate platform ca 10 km to the south, and is interpreted as resulting from flooding of the platform top. Platform inundation allows carbonate muds to be winnowed from their original shallow‐water environment of deposition, suspended in the water column, and redeposited onto the proximal slopes and within the basin. Sharp increases in aragonite content at the beginning of each highstand interval can be used to estimate the approximate sea‐level range when platform flooding occurred; results show that the depth of the platform top has likely changed little over the past 1 Myr due to balanced aggradation and subsidence. Previously hypothesized large‐scale aragonite dissolution cycles are evidenced by a disproportionally low aragonite increase during MIS 11. This study provides a new, exceptionally long record of highstand shedding, expanding the known occurrences of the process to the southern Indian Ocean and supporting its importance as a globally significant depositional mechanism that impacts deep‐sea stratigraphic records.

Marine carbonate factories: Review and update

“…Other windward-leeward variations in sediment export are shown by the progradation and aggradation patterns on Great Bahama Bank closing one of the intraplatform seaways (Eberli & Ginsburg, 1987). While T-factories export abundant sediment from shallow-water areas towards their surroundings, which may be up to 50 km as discussed for Pedro Bank (Caribbean) by Andresen et al (2003) or even over 50 km (south-west Indian Ocean; Counts et al, 2019;Jorry et al, 2020), one could describe the overall sedimentation pattern as 'Spread' ; Fig. 7).…”

“…While T‐factories export abundant sediment from shallow‐water areas towards their surroundings, which may be up to 50 km as discussed for Pedro Bank (Caribbean) by Andresen et al . (2003) or even over 50 km (south‐west Indian Ocean; Counts et al ., 2019; Jorry et al ., 2020), one could describe the overall sedimentation pattern as ‘Spread’ (Reijmer, 2016; Fig. 7).…”

Linking carbonate sediment transfer to seafloor morphology: Insights from Exuma Valley, the Bahamas

“…Strontium (Sr) and calcium (Ca) concentrations were acquired at a centimetre‐scale resolution with an XRF core scanner for KS24. Strontium was demonstrated as a proxy for aragonite content in tropical carbonate factories (Counts et al ., 2019). Aragonite content is widely used as a proxy for glacial and interglacial cyclicity (Droxler & Schlager, 1985; Roth & Reijmer, 2005).…”

Depositional and geomorphic patterns of mixed calciclastic‐siliciclastic systems on a deep‐water Equatorial Margin

“…Published work aiming to understand deep-water carbonate depositional systems include vintage articles with initial descriptions of carbonate slopes (e.g. Coniglio et al, 1992;Ditty et al, 1977;James & Mountjoy, 1983;Kenter, 1990;Ravenne et al, 1985), important compilations (Payros & Pujalte, 2008;Playton et al, 2010;Reijmer, Mulder, et al, 2015) and recent studies in which depositional models separate carbonate settings from their siliciclastic counterparts (Counts et al, 2019;Jorry et al, 2020;Moscardelli et al, 2019;Mulder et al, 2014). For instance, the modern and ancient Bahamian sedimentary system has been crucial to understand carbonate platform-to-basin sedimentation patterns, and recognise that carbonate-lobe and channel systems are able to develop in deep-water basins (Betzler et al, 1999(Betzler et al, , 2014Bornhold & Pilkey, 1971;Crevello & Schlager, 1980;Eberli et al, 1997Eberli et al, , 2005Mulder et al, 2012Mulder et al, , 2014Reijmer, Mulder, et al, 2015;Wunsch et al, 2017).…”