The emergence of Miocene reefs in South China Sea and its resilient adaptability under varying eustatic, climatic and oceanographic conditions

Abstract

During the Miocene, extensive carbonate deposition thrived over wide latitudinal ranges in SoutheastAsia despite perturbations of the global climate and thermohaline circulation that affected the Asian continent. nevertheless, the mechanisms of its emergence, adaptability in siliciclastic-dominated margins and demise, especially in southern South china Sea (ScS), are largely speculative and remains enigmatic along with a scarcity of constraints on paleoclimatic and palaeoceanographic conditions. Here we show, through newly acquired high-resolution geophysical data and accurate stratigraphic records based on strontium isotopic dating, the evolution of these platforms from ~15.5-9.5 Ma is initially tied to tectonics and eustasy, and ultimately, after ~9.5 Ma, to changes in the global climate patterns and consequent palaeoceanographic conditions. our results demonstrate at least two paleodeltas that provided favourable substratum of elevated sand bars, which conditioning the emergence of the buildups that inadvertently mirrored the underlying strata. We show unprecedented evidences for ocean current fluctuations linked to the intensification of the Asian summer monsoon winds resulting in the formation of drifts and moats, which extirpated the platforms through sediment removal and starvation. this work highlights the imperative role of palaeoceanography in creating favourable niches for reefal development that can be applicable to carbonate platforms elsewhere.A gargantuan modification of the planetary climate system and the thermohaline circulation patterns occurred in the Cenozoic with the inflection point being diffused from exceptionally critical tectonic processes that affected Asia 1,2 . At ca. 24 Ma, in close proximity to the Oligocene-Miocene boundary, the continent experienced a transformation of climatic processes from a latitudinal zonal circulation pattern to a monsoon-dominated configuration along with the evanescing of an extensively prevalent subtropical-aridity across Asia and the inception of aridity that was exclusively restricted to the hinterland of eastern Asia 3 . The Asian continent experienced a dynamic climate transition that was instigated by the Paleocene-Eocene collision of the Indian Plate with Asia and the resulting progressive uplift of the Tibetan Plateau (TP). This caused an array of feedbacks that significantly strengthened monsoon-inducing atmospheric circulation with each of its major orogenic pulses 4 (i.e., at (i) ca. and (iii) ca. 15-10 Ma [refer to Fig. 1 for (ii) and (iii)]). Over a span of ~30 Ma, the stepwise exhumation of the TP governed an accelerated amplification of firstly, the Indian Summer Monsoon (ISM) and the Somali Jet with the initial pulse of uplift; secondly, the Southeast Asian Monsoon, the East Asian Summer Monsoon (EASM) and the East Asian Winter Monsoon (EAWM) with 40% uplift of the TP; and lastly, the further intensification of the EASM and EAWM with 80% uplift of the TP 5,6 (Fig. 1). This last uplift

The Miocene: The Future of the Past

“…Overall, the distribution of carbonate reef environments was controlled largely by plate tectonics and eustasy from ∼15.5 to 9.5 Ma and thereafter by changes in global climate patterns and consequent paleoceanographic conditions (Mathew et al., 2020; Renema et al., 2008).…”

Seismic stratigraphy and sedimentology of a Miocene carbonate platform in Luconia, South China Sea

“…The collision of the Indian Plate with Asia (Guo et al, 2008; Hall, 2009; Tada & Murray, 2016), had a strong impact on the palaeoclimate and palaeogeography of the South China Sea, along with an undeniable role played by local tectonic processes (Mathew et al, 2020). The Early Miocene rifting of the SCS resulted in numerous horst structures, which became the most suitable substratum for coral development (Ting et al, 2018).…”

“…The Early Miocene rifting of the SCS resulted in numerous horst structures, which became the most suitable substratum for coral development (Ting et al, 2018). On the other hand, the grabens were the locus of interplatform seaways (Mathew et al, 2020) and siliciclastic deposition (Figure 9a). Syn‐depositional faulting had a dominant influence on early carbonate growth (Briais et al, 1993; Bachtel et al, 2004; Hall, 1996; Hutchison, 1989; Jamaludin et al, 2014; James, 1983; Mat‐Zin, 1997; Rankey et al, 2019; Ting et al, 2012), especially in the Early Middle Miocene.…”

“…While the causes of drowning cannot be confidently attributed to one single event, the controls could be a combination of multiple factors. Despite the fact that an increasing influx of allochthonous siliciclastic sediments that can decrease the water quality (Vahrenkamp et al, 2004; Zampetti et al, 2004), reef systems appear to be able to survive in inhospitable conditions as demonstrated by studies of carbonate growth in high turbidity waters (Mathew et al, 2020; Maxwell, 1970; Syahrir et al, 2018; Wilson, 2005). Other factors could be responsible for the observed drowning including rapid sea‐level rise that could have modified the depth of the photic zone, which can be a reason for platform demise and an abruptly overwhelming supply of nutrients that can negatively affect carbonate growth (Shahzad et al, 2018).…”

“…Other factors could be responsible for the observed drowning including rapid sea‐level rise that could have modified the depth of the photic zone, which can be a reason for platform demise and an abruptly overwhelming supply of nutrients that can negatively affect carbonate growth (Shahzad et al, 2018). However, our recent work demonstrates that one of the most crucial factors of carbonate platform demise in Luconia region is the domination of monsoonal wind‐driven oceanic currents regulated by planetary climatic circulation (Mathew et al, 2020).…”