Seismic stratigraphy of the Frontal Hawaiian Moat: implications for sedimentary processes at the leading edge of an oceanic hotspot trace

Multi-channel seismic imaging reveals the seismic stratigraphy and associated sedimentary processes of the Frontal Hawaiian Moat (FHM) to the southeast of the island of Hawaii. Two sedimentary units are defined: (1) a basal layer of pelagic sediment draping the oceanic basement and (2) a wedge of volcaniclastic material infilling the FHM and onlapping the Frontal Hawaiian Arch. Three distinct seismic facies within the volcaniclastic unit are recognized: (A) areas of chaotic or incoherent reflections interpreted as proximal debris avalanche or slump deposits; (B) groups of hummocky and distorted reflections interpreted as distal debris avalanche or debris flow deposits; and (C) regions of parallel and laterally continuous reflections interpreted as turbidite deposits. The distribution of these facies delineates slope apron, proximal basin, and distal basin depositional environments (respectively) within the FHM. The northwest drift of the Pacific Plate over the Hawaiian hot spot results in the apparent southeasterly migration of the Hawaiian chain. Advancement of the depositional environments within the FHM occurs as individual volcanoes evolve, erode, and are superseded by new volcanic centers. The interplay between depositional processes and tectonic forces (plate motion and lithospheric flexure) predicts a coarsening-upward stratigraphy within the FHM. The combined accumulation of pelagic and volcaniclastic sediment defines a heterogeneous, and potentially unstable, layer of low strength material beneath the volcanic edifice that may influence the mobility of the island flanks.