Occurrence of active gas hydrate mounds in the southwestern slope of the Chukchi Plateau, Arctic Ocean

Abstract

This study documents the discovery of mound morphologies containing gas hydrate and methane-derived authigenic carbonate (MDAC) in the southwestern slope of the Chukchi Plateau, during the IBRV Araon expeditions in 2016 and 2018. A multibeam bathymetric surveying was the basis for a new and detailed rendering around the mounds. Sub-bottom profiles and site-targeted gravity cores were also collected across these mounds which were located at water depths between 780 m and 580 m. Mounds are characterized by a circular plan shape of hundreds of meters in width and tens of meters in height. Below the mounds, gas accumulation in the sediment produces acoustic blanking in seismic data. MDACs are identified along the core collected from the top of a mound structure, indicating past methane oxidation processes. Gas hydrate has also been observed at the bottom of the core. Reverse geothermal gradients of the mound support the idea of active presentday seepage. We argue that the prolonged seepage activity of methane-rich fluid, possibly related to the formation of the rifted North Chukchi Basin, has led to the formation of the gas hydrate mounds, named hereafter the Araon Mounds, in the vicinity of the basin margin.

Earth degassing in the Arctic: comprehensive analysis of factors of powerful gas emission in the Laptev Sea

“…Доступные результаты исследований δ 13 C (CH 4 ), проведенные по сипам газа в морях Восточной Арк тики вдали от современного положения речных дельт, практически повсеместно показали его глубинный генезис [31; 38; 46]. При этом в Чукотском бассейне δ 13 C (CH 4 ) изменялся от -63,6‰ до -55,6‰ [38], что близко к данным по метану биогенного генезиса с глубин 500-1300 м сеноманских отложений севера Западной Сибири [3; 4]. В абсолютном большинстве исследований [31] в море Лаптевых в придонных осадках и сипах был обнаружен термогенный метан с δ 13 C (CH 4 ) от -43‰ до -37‰, а также более тяжелые молекулярные соединения (этан, пропан и др.).…”

Heat Flow Distribution in the Chukchi Borderland and Surrounding Regions, Arctic Ocean

“…The M07 is underlain by continuous thick sediment and a smooth basement (Hegewald, 2012;Hegewald & Jokat, 2013) which is a sedimentary environment that facilitates reliable heat flow measurements (Sclater et al, 1976). Site ARA09C01HFP from Kim et al (2020) is located ∼70 km south of M07 and its thermal gradient (56.5 mK/m) is similar to that of M07, although the associated conductivity has not been published yet.…”

“…The stars and hexagons indicate the heat flow sites from O' Regan et al (2016) and the global heat flow database (IHFC, 2012), respectively. The eight sites at roughly 81°N (Jokat, 2009) and one site in the Chukchi Abyssal Plain (Kim et al, 2020) without thermal conductivity are indicated by small octagons. The bathymetry contour interval is 1,000 m. AR, Alpha Ridge; CAA, Canadian Arctic Archipelago; CAP, Chukchi Abyssal Plain; CB, Canada Basin; CP, Chukchi Plateau; EI, Ellesmere Islands; FJ, Franz Josef Island; HT, Hanna Trough; KPR, Knipovich Ridge; LR, Lomonosov Ridge; MB, Makarov Basin; MR, Mendeleev Ridge; NCB, North Chukchi Basin; NCBL, Northern Chukchi Borderland; NSI, New Siberia Island; NWB, Northwind Basin; NWR, Northwind Ridge.…”

Evidence of Gas Emissions from Permafrost in the Russian Arctic

“…Gas venting from shelf sediments has been attributed to the dissociation of gas hydrates in paleopermafrost [35][36][37][38]. The relation of methane venting from bottom sediments with gas hydrates on the Russian Arctic shelf has received no direct proof though, in the absence of test boreholes [39,40], but it was recently reported regarding the continental slope of the Russian Arctic in Chukchi Sea [41], and from other Arctic areas (Spitsbergen, Beaufort Sea, etc.) [42,43].…”