New insights into rift evolution from data-constrained burial and thermal histories at the northern South China Sea margin

Andrea Schito , Geofroy Mohn, Zhibin Wen, Sveva Corrado, Michael Nirrengarten, Laura Gutierrez Garcia, Stephen Alan Bowden

The evolution of the rifted margin of the northern South China Sea challenges predictions of previous models but a knowledge gap still exists regarding how thermal history varies at different locations and times of rifting. International Ocean Discovery Program (IODP) Expeditions 367/368/368X collected samples of sediment that can be used to model the thermal evolution at different rifting stages in the distal margin and oceanic crust. Modelling results outline a thermal history driven by the interplay of different tectonic processes that are sometimes at odds with the main theoretical models. The most proximal location has a burial history that includes the unroofing of ~3km of sediment before the increase of heat flow during rifting and break up prior to cooling to the present day. In the more distal part, short, localised peaks in heat flow due to syn-rift magmatism are recorded while, the oceanic crust has a thermal regime decoupled from that of the continental section and here the rate of cooling abruptly decreased in final post-rift phases. Thus, while the transect drilled in IODP 367/368 may represent a transition from continental to ocean crust, the thermal regimens sampled by are not end-members in a simple continuum and instead capture fundamental steps in the thermal evolution of the distal rifted margin of the northern South China Sea. On a global scale, this dataset represents one of the most complete samplings of a distal rifted margin providing critical new constrains on the thermal evolution during formation of rifted margins.