Large Igneous Provinces, Mantle Plumes and Uplift: A Sedimentological perspective

Significant pre-volcanic uplift of the lithosphere is one of the expected consequences of mantle plume upwelling. Many major mafic/ultramafic lavas have been attributed to mantle plumes that are expected to produce crustal uplift (doming) preceding the major phase of volcanism. Such pre-volcanic uplift would have significant consequences on the regional sedimentation pattern. Subsequent erosion may remove much of the volcano-sedimentary record of domal uplift. However, sedimentologists can identify progressive shallowing of palaeogeography prior to volcanism and distinctive palaeocurrent patterns if these exist, and this may provide constraints on plume interpretations of the volcanic episode. It is difficult to defend a LIP-mantle plume connection where pre-volcanic lithospheric uplift is absent. This is particularly true for continental flood basalts. The sedimentological and stratigraphic criteria proposed for tracing LIP-plume connections are somewhat generalized, and will not all be useful at a given location. For example, progressive shallowing of palaeogeography as a consequence of plume-induced lithospheric uplift should be clear in a marine depositional setting (e.g., in the transition from deep to shallow marine, or marine to terrestrial palaeogeography). In a continental depositional setting, such evidence is less likely to be found, however. This is because the depositional surface is already well above mean sea level (the base level of erosion) and its preservation potential is small. Unlike the case of marine depositional settings, an erosional unconformity/sequence boundary will thus not develop because the depositional surface is already subaerially exposed. The claim that the sedimentary record provides independent supporting evidence for mantle plume influence on the generation of LIPs, is not always true. The genetic linkage between CFBs and mantle plumes is at best difficult to establish from sedimentological analysis alone.