Tidal dynamics and mangrove carbon sequestration during the Oligo–Miocene in the South China Sea

Abstract

Modern mangroves are among the most carbon-rich biomes on Earth, but their long-term (≥106 years) impact on the global carbon cycle is unknown. The extent, productivity and preservation of mangroves are controlled by the interplay of tectonics, global sea level and sedimentation, including tide, wave and fluvial processes. The impact of these processes on mangrove-bearing successions in the Oligo–Miocene of the South China Sea (SCS) is evaluated herein. Palaeogeographic reconstructions, palaeotidal modelling and facies analysis suggest that elevated tidal range and bed shear stress optimized mangrove development along tide-influenced tropical coastlines. Preservation of mangrove organic carbon (OC) was promoted by high tectonic subsidence and fluvial sediment supply. Lithospheric storage of OC in peripheral SCS basins potentially exceeded 4,000 Gt (equivalent to 2,000 p.p.m. of atmospheric CO2). These results highlight the crucial impact of tectonic and oceanographic processes on mangrove OC sequestration within the global carbon cycle on geological timescales.

Controls on tidal sedimentation and preservation: Insights from numerical tidal modelling in the Late Oligocene–Miocene South China Sea, Southeast Asia

“…Collins et al . ). Rock data include grain size, tide‐generated cross‐lamination (ripples) and/or cross‐bedding (mainly in siltstone–sandstone facies), mangrove pollen acmes (mainly in mudstones and/or coals), and the occurrence of paralic, mangrove‐influenced coals and source‐rocks (coals or carbonaceous mudstones).…”

“…Longley, ; Hall, ; Morley, ). Tectonics and thermal subsidence caused significant (>4 to 5 km) subsidence and preservation of Oligo–Miocene, shoreline–shelf successions in several SCS basins (Longley, ; Doust & Sumner, ; Morley, ), many of which show evidence of tidal influence (Collins et al ., ).…”

A New Vegetation Index to Detect Periodically Submerged Mangrove Forest Using Single-Tide Sentinel-2 Imagery

“…. ,k and j = 1,2; and let π (1) and π (2) denote the weights of the distributions p (1) and p (2) , satisfying the constraints π (1) + π (2) = 1 and 0 ≤ π ( j) ≤ 1. Then the Jensen-Shannon divergence D between the probability distributions p (1) and p (2) with weights π (1) and π (2) is defined by [46]:…”

“…Mangrove forest are highly productive ecosystems with significant ecological and socio-economic importance in the world [1,2]. However, over the past century, these forests have declined at an alarming rate that is more rapid than that of inland tropical forests [3].…”

Relative sea‐level change regulates organic carbon accumulation in coastal habitats

“…Rapid sediment accretion was responsible for the rapid C org accumulation under subtidal conditions (Figure 4). The low magnetic susceptibility of these deposits suggests that the SAR was enhanced by the greater water depth and associated attenuation of wave energy and bottom velocities but not by an abrupt increase in riverine sediment load (Figure 7) (Collins et al, 2017;Morris, Sundareshwar, Nietch, Kjerfve, & Cahoon, 2002;Woodroffe et al, 2016).…”