Growth and demise of Cenozoic isolated carbonate platforms: New insights from the Mozambique Channel seamounts (SW Indian Ocean)

Abstract

International audienceAlthough long-term evolutions of isolated shallow-water carbonate platforms and demise episodes leading to guyot formation have been the subject of numerous studies during the last decades, their driving processes are still the subject of active debates. The Mozambique Channel (SW Indian Ocean) is characterized by several flat-topped seamounts ranging from 11°S to 21°S in latitudes. Based on a comprehensive geomorphologic study and on dredged samples analysis, we show that these features correspond to tropical isolated shallow-water carbonate platforms. Coupling strontium isotopy and foraminifera biostratigraphy, well-constrained chronostratigraphy results indicate that shallow-water carbonate production started in the Mozambique Channel during distinct Cenozoic periods ranging from Paleocene to Early Miocene. Our data also demonstrate that these carbonate platforms were subsequently characterized by different evolutions locally marked by tectonic and rejuvenated volcanism. While some of them kept developed until present days, forming modern carbonate systems, some others were drowned during Late Neogene and subsided to form guyots. Although different factors can be discussed, tectonic and volcanism appear as good potential triggers for demise episodes during Late Miocene-Early Pliocene times. Chronology and location of this geodynamical activity tend to emphasize influence of East African rift system until southern Mozambique Channel

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

“…0.5-2 mm/yr for bioclastic shoals; Strasser & Samankassou, 2003), demonstrating that sedimentation could have easily kept pace with any ongoing platform subsidence. Courgeon et al (2016) estimate the rate of subsidence for the nearby Glorieuses platform at 0.01-0.015 mm/yr, in line with these other estimates.…”

“…Courgeon et al. () estimate the rate of subsidence for the nearby Glorieuses platform at 0.01–0.015 mm/yr, in line with these other estimates.…”

Deep‐water dunes on drowned isolated carbonate terraces (Mozambique Channel, south‐west Indian Ocean)

“…It originated as a shallow‐water carbonate platform (Fig. ; Courgeon et al ., ). The southern central part of the Mozambique Channel contains both a modern atoll (Bassas da India), and several drowned carbonate platforms (the Hall and Jaguar banks and part of Bassas da India) that originally developed atop submarine volcanoes (Fig.…”

“…The southern central part of the Mozambique Channel contains both a modern atoll (Bassas da India), and several drowned carbonate platforms (the Hall and Jaguar banks and part of Bassas da India) that originally developed atop submarine volcanoes (Fig. ; Courgeon et al ., ). The initiation of shallow‐water carbonate sedimentation is thought to have taken place at the Sakalaves Seamount and in the Southern Mozambique Channel during Oligocene and Early Miocene times, respectively (Courgeon et al ., ).…”

Evolution and Geological Significance of Larger Benthic Foraminifera

“…Tracing the stratigraphic distribution of the larger benthic foraminifera allows the understanding of the impact of climate, tectonic activity and volcanism on long-term (i.e. millions years) evolution of these shallow-water carbonate platforms (Courgeon et al, 2016(Courgeon et al, , 2017Gold et al, 2017aGold et al, , 2017b. Larger foraminifera and planktonic foraminifera overlap in occurrence in many localities allowing direct comparison of larger foraminifera "letter stages" biozones with oceanic planktonic scales (BouDagher-Fadel, 2002;BouDagher-Fadel, 2013, 2015Sharaf et al, 2013).…”