Geological Processes Affecting the Shallow Seafloor Temperature Fields: Results from 2D and 3D Seismic Reflection Data Offshore SW Taiwan

Abstract:

Seafloor heat flow measurements provide fundamental geophysical information that can be used to better understand tectonic processes. Regional heat flow patterns have been successfully used to study the cooling of the oceanic lithosphere, exhumation of deep crustal materials, strength of the faults, and other geological processes. However, sometimes there are variations of heat flows within a small area, making the interpretation of the heat flows difficult. Here we study the geological processes that can cause such variations. Over the last two decades, we have collected many dense 2D and 3D seismic reflection data offshore SW Taiwan and there is a wide-spread bottom-simulating reflector (BSR) found in the seismic profiles. The BSR is interpreted as associated with the base of the gas hydrate stability zone, and can be used to infer the temperature fields at shallow oceanic crust using a hydrate phase diagram. Such a dense and wide-spread dataset provides an unprecedented opportunity to study processes that can affect temperature fields in scales less than a kilometer. Here we show evidence of bathymetry-induced temperature perturbations at shallow oceanic crust by comparing the BSR-based temperature data with the temperature derived from steady-state 3D finite element modeling. We have also documented focused fluid flow migration along faults and fissures based on elevated temperature fields near those geological features. We also found seismic evidence of abnormal high heat flows caused by rapid erosion. Our results demonstrate that sometimes it is necessary to correct those effects before the heat flow data can be used for regional studies. Our study is among the first to provide observational data to study small-scale geological processes affecting seafloor temperature fields. Such information might also be important for gas and oil reservoir studies.