oa Heat-flow measurements: Fundamental information for structural and geodynamic interpretation

Seismic data provide clear images of the subsurface geology that often clarify geodynamic processes. In general, it is a crucial advantage to have an even better understanding of the dynamic processes of pore water or hydrocarbons. Marine heat-flow measurements provide additional information regarding the dynamics of sedimentary basins or continental shelves at regional or local scales. For example, heat-flow measurements at the South American active continental margin revealed convective water movements along the decollement zone. On a smaller scale, dewatering along a fault zone was detected by increased heat-flow values. Together with δ13C analysis of carbonate samples, a pathway of hydrocarbons through a gas hydrate stability zone could be proven. A small-scale example for the use of heat-flow measurements was the Haakon Mosby mud volcano off northern Norway. From measurements across the volcano, expulsion rates could be determined. On a regional scale, thermal conditions of continent-ocean transition are often unclear, especially if borehole information is scarce in undeveloped basins. As geothermal heat flow is a measure for crustal age, measurements can help to decipher the tectonic evolution of continental margins. On these different spatial scales, from sites as small as the Haakon Mosby mud volcano to basin-wide exploration, the measurements of the thermal field assists in answering questions regarding fluid convection and tectonic history at a relatively low cost.