Abstract:This study describes a previously unobserved reflection seismic configuration comprising a honeycomb planform and a repeated erosion/infill cross‐section, based on high‐resolution three‐dimensional/two‐dimensional seismic data and bathymetric data. The honeycomb structures cover an area of more than 5000 km2 and are developed within the Late Miocene to recent deep‐water sediments of the north‐western South China Sea. Linear erosional troughs up to 10 km long and 1 km wide are widely developed in this area, are… Show more
“…A similar kilometer-scale, seafloor HP was previously interpreted to originate from smaller counterparts developed in underlying sedimentary units as a result of a sediment drift depositional pattern (Sun et al, 2017). This pattern is characterized by wave-like geometries corresponding to cut-and-fill erosional features with honeycomb planforms.…”
Section: Page Of 27supporting
confidence: 60%
“…3A) carved into u1 (Fig. 4B, zoom2 and zoom3) are, however, deeper (~200-300 m) than those (~60 m) described by Sun et al (2017), suggesting that other important processes are involved.…”
Section: Page Of 27mentioning
confidence: 78%
“…Only a few cases of kilometer-scale honeycomb pattern (HP) on the seafloor have been reported along continental margins and generally into siliceous or mudstonedominated sediments. The main examples are (1) kilometer-scale seabed high-centered polygons (Berndt et al, 2012) outlined by 20-m-deep, elongated pockmarks, formed by sediment contraction related to fluid circulation along polygonal faults; and (2) polygonal crests separating hectometer-to kilometer-scale, 60-m-deep depressions formed by longterm unstable bottom currents (Sun et al, 2017). Here, we used new multibeam data collected during the 2012 ATACAMES cruise (RV L'Atalante) on the Carnegie Ridge offshore Ecuador (http://campagnes.flotteoceanographique.fr/campagnes/12010010/; Fig.…”
Based on swath bathymetry, two-dimensional, high-resolution seismic reflection profiles, and Ocean Drilling Program/Deep Sea Drilling Project (ODP/DSDP) data, we describe a seafloor honeycomb pattern and propose a model for its formation in Pliocene-Miocene Page 2 of 27 carbonate deposited on the uneven oceanic basement of the Carnegie Ridge (offshore Ecuador). Hydrothermal fluids derived from the basement aquifer fractured and dissolved carbonate sediment, creating seafloor pits above basements highs. Fluids expelled along polygonal faults may have assisted the nucleation of seafloor depressions. At the Pliocene-Pleistocene boundary, strong bottom currents scoured previously damaged sediments, enlarging the initial depressions and producing the seafloor honeycomb pattern. This regional erosive episode was contemporaneous with the final closing of the Isthmus of Panama and the clogging of the Ecuador Trench by the subduction of the Carnegie Ridge, so that the honeycomb pattern may be viewed as a regional marker of these two geodynamic events.
“…A similar kilometer-scale, seafloor HP was previously interpreted to originate from smaller counterparts developed in underlying sedimentary units as a result of a sediment drift depositional pattern (Sun et al, 2017). This pattern is characterized by wave-like geometries corresponding to cut-and-fill erosional features with honeycomb planforms.…”
Section: Page Of 27supporting
confidence: 60%
“…3A) carved into u1 (Fig. 4B, zoom2 and zoom3) are, however, deeper (~200-300 m) than those (~60 m) described by Sun et al (2017), suggesting that other important processes are involved.…”
Section: Page Of 27mentioning
confidence: 78%
“…Only a few cases of kilometer-scale honeycomb pattern (HP) on the seafloor have been reported along continental margins and generally into siliceous or mudstonedominated sediments. The main examples are (1) kilometer-scale seabed high-centered polygons (Berndt et al, 2012) outlined by 20-m-deep, elongated pockmarks, formed by sediment contraction related to fluid circulation along polygonal faults; and (2) polygonal crests separating hectometer-to kilometer-scale, 60-m-deep depressions formed by longterm unstable bottom currents (Sun et al, 2017). Here, we used new multibeam data collected during the 2012 ATACAMES cruise (RV L'Atalante) on the Carnegie Ridge offshore Ecuador (http://campagnes.flotteoceanographique.fr/campagnes/12010010/; Fig.…”
Based on swath bathymetry, two-dimensional, high-resolution seismic reflection profiles, and Ocean Drilling Program/Deep Sea Drilling Project (ODP/DSDP) data, we describe a seafloor honeycomb pattern and propose a model for its formation in Pliocene-Miocene Page 2 of 27 carbonate deposited on the uneven oceanic basement of the Carnegie Ridge (offshore Ecuador). Hydrothermal fluids derived from the basement aquifer fractured and dissolved carbonate sediment, creating seafloor pits above basements highs. Fluids expelled along polygonal faults may have assisted the nucleation of seafloor depressions. At the Pliocene-Pleistocene boundary, strong bottom currents scoured previously damaged sediments, enlarging the initial depressions and producing the seafloor honeycomb pattern. This regional erosive episode was contemporaneous with the final closing of the Isthmus of Panama and the clogging of the Ecuador Trench by the subduction of the Carnegie Ridge, so that the honeycomb pattern may be viewed as a regional marker of these two geodynamic events.
“…Collectively, the sedimentation rates and the present-day geothermal gradient are both high in the Qiongdongnan Basin [38]. The thick sediment sequences, high geothermal gradient along with faulting and/or diapirism, have facilitated the generation and migration of the hydrocarbons in the basin [39]. The widely distributed bottom-simulating reflectors and gas chimneys identified in the Qiongdongnan Basin were linked to the accumulation of gas hydrate [40,41].…”
The Haima cold seeps are active cold seep areas that were recently discovered on the northwestern slope of the South China Sea (SCS). Three piston cores (CL30, CL44, and CL47) were collected within an area characterized by bottom simulating reflectors to the west of Haima cold seeps. Porewater profiles of the three cores exhibit typical kink-type feature, which is attributed to elevated methane flux (CL30) and bubble irrigation (CL44 and CL47). By simulating the porewater profiles of SO42-, CH4, PO43-, Ca2+, Mg2+, and dissolved inorganic carbon (DIC) in CL44 and CL47 using a steady-state reaction-transport model, we estimated that the dissolved SO42- was predominantly consumed by anaerobic oxidation of methane (AOM) at rates of 74.3 mmol m−2 yr−1 in CL44 and 85.0 mmol m−2 yr−1 in CL47. The relatively high AOM rates were sustained by free gas dissolution rather than local methanogenesis. Based on the diffusive Ba2+ fluxes and the excess barium contents in the sediments slightly above the current SMTZ, we estimated that methane fluxes at core CL44 and CL47 have persisted for ca. 3 kyr and 0.8-1.6 kyr, respectively. The non-steady-state modeling for CL30 predicted that a recent increase in upward dissolved methane flux was initiated ca. 85 yr ago. However, the required time for the formation of the barium front above the SMTZ at this core is much longer (ca. 2.2-4.2 kyr), which suggests that the depth of SMTZ possibly has fluctuated due to episodic changes in methane flux. Furthermore, using the model-derived fractions of different DIC sources and the δ13CDIC mass balance calculation, we estimated that the δ13C values of the external methane in cores CL30, CL44, and CL47 are -74.1‰, -75.4‰, and -66.7‰, respectively, indicating the microbial origin of methane. Our results suggest that methane seepage in the broader area surrounding the Haima cold seeps probably has persisted at least hundreds to thousands of years with changing methane fluxes.
“…Zhu et al, 2009 16 ). Previous research has revealed contourite deposition (honeycomb structures) west of the Zhongjianbei platform 17 , and contourite channels around the Triton and Zhongjian platforms 18 – 20 . Figure 2 (a) Multibeam bathymetric map; and b) Morphosedimentary interpretation including large features.…”
The North Pacific subtropical gyre (NPSG) plays a major role in present global ocean circulation. At times, the gyre has coursed through the South China Sea, but its role in the evolutionary development of that Sea remains uncertain. This work systematically describes a major shift in NPSG paleo-circulation evident from sedimentary features observed in seismic and bathymetric data. These data outline two contourite depositional systems—a buried one formed in the late Miocene, and a latest Miocene to present-day system. The two are divided by a prominent regional discontinuity that represents a major shift in paleo-circulation during the latest Miocene (~ 6.5 Ma). The shift coincides with the further restriction of the South China Sea with respect to the North Pacific due to the formation of the Luzon Strait as a consequence of further northwest movement of the Philippine Sea plate. Before that restriction, data indicate vigorous NPSG circulation in the South China Sea. Semi-closure, however, established a new oceanographic circulation regime in the latest Miocene. This work demonstrates the significant role of recent plate tectonics, gateway development, and marginal seas in the establishment of modern global ocean circulation.
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