Late Cenozoic Sediment Provenance in the Northern Canterbury Basin, Aotearoa New Zealand

Late Cenozoic strata of the northern Canterbury Basin record uplift and erosion of mountain ranges adjacent to the transition from oblique subduction to strike‐slip on the Australian–Pacific plate boundary. Using the provenance of conglomerate clasts and sandstone samples, we reconstruct sediment transport pathways and, by inference, exhumation and reverse faulting during plate boundary development in the northeastern South Island. In the Middle–Late Miocene, isolated topographic highs within the modern Marlborough Fault System are interpreted to have supplied sediment into the northern Canterbury Basin, with sediment transported towards the southwest and southeast. By the Late Pliocene–Early Pleistocene, the provenance signature can be explained using sediment transport pathways similar to modern rivers, with sediment being supplied into the northern Canterbury Basin towards the southeast from exhumation adjacent to the Alpine Fault. A drainage reorganisation prior to the Late Pliocene was possibly driven by a southwestward transfer of exhumation onto the Alpine Fault. Our study also suggests the existence of a northeast‐flowing longshore current from at least the Middle Miocene to the present. A minor volume of sand‐sized grains has been recycled from the underlying cover stratigraphy but is considered unlikely to alter our provenance interpretations.