Episodic Venting of a Submarine Gas Seep on Geological Time Scales: Formosa Ridge, Northern South China Sea.

Kunath, Pascal, Crutchley, Gareth J. , Chi, Wu‐Cheng, Berndt, Christian , Liu, Char‐Shine, Elger, Judith , Klaeschen, Dirk and Bohrmann, Gerhard (2022) Episodic Venting of a Submarine Gas Seep on Geological Time Scales: Formosa Ridge, Northern South China Sea. Journal of Geophysical Research: Solid Earth, 127 (9). Art.Nr. e2022JB024668. DOI 10.1029/2022JB024668.

[thumbnail of JGR Solid Earth - 2022 - Kunath - Episodic Venting of a Submarine Gas Seep on Geological Time Scales Formosa Ridge .pdf] Text
JGR Solid Earth - 2022 - Kunath - Episodic Venting of a Submarine Gas Seep on Geological Time Scales Formosa Ridge .pdf - Published Version
Restricted to Registered users only

Download (4MB) | Contact

Supplementary data:

Abstract

The Formosa Ridge cold seep is among the first documented active seeps on the northern South China Sea passive margin slope. Although this system has been the focus of scientific studies for decades, the geological factors controlling gas release are not well understood due to a lack of constraints of the subsurface structure and seepage history. Here, we use high-resolution 3D seismic data to image stratigraphic and structural relationships associated with fluid expulsion, which provide spatio-temporal constraints on the gas hydrate system at depth and methane seepage at modern and paleo seafloors. Gas has accumulated beneath the base of gas hydrate stability to a critical thickness, causing hydraulic fracturing, propagation of a vertical gas conduit, and morphological features (mounds) at paleo-seafloor horizons. These mounds record multiple distinct gas migration episodes between 300,000 and 127,000 years ago, separated by periods of dormancy. Episodic seepage still seems to occur at the present day, as evidenced by two separate fronts of ascending gas imaged within the conduit. We propose that episodic seepage is associated with enhanced seafloor sedimentation. The increasing overburden leads to an increase in effective horizontal stress that exceeds the gas pressure at the top of the gas reservoir. As a result, the conduit closes off until the gas reservoir is replenished to a new (greater) critical thickness to reopen hydraulic fractures. Our results provide intricate detail of long-term methane flux through sub-seabed seep systems, which is important for assessing its impact on seafloor and ocean biogeochemistry.

Key Points

- Gas has accumulated beneath the base of gas hydrate stability, causing vertical gas conduit formation and seabed mounds

- Mounds imaged within the conduit record episodic seepage between 300 and 127 kyrs ago

- Quiescence may be associated with enhanced seafloor sedimentation that increases effective stress at the top of the gas reservoir

Document Type: Article
Keywords: gas hydrate, gas conduit, hydraulic fracturing, episodic venting, sedimentary processes, offshore Taiwan
Research affiliation: MARUM
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Corresponding Author:
Corresponding Author Name
GEOMAR ID
Affiliation
Kunath, Pascal
Kunath, Pascal
FB4-GDY Marine Geodynamics
Main POF Topic: PT8: Georesources
Refereed: Yes
Open Access Journal?: No
Publisher: AGU (American Geophysical Union), Wiley
Related URLs:
Projects: MOST
Expeditions/Models/Experiments:
Date Deposited: 16 Sep 2022 10:45
Last Modified: 20 Sep 2022 11:26
URI: https://oceanrep.geomar.de/id/eprint/57032

Actions (login required)

View Item View Item