The Source is in the Sink: Deep-Water Deposition From a Submarine Volcanic Arc, Taranaki Basin, New Zealand

Abstract

Submarine volcanoes produce sediment that originates and remains in a deep-water setting, never escaping the water column. This situation puts a twist on the idea of source-to-sink pathways, where both source and sink are in the submarine realm. Submarine volcanoes may play a significant role in basin sedimentation, but direct observation of sediment production and dispersal from submerged volcanoes is expensive and logistically difficult. We analyze the Mohakatino Formation, a submarine fan succession composed of sediment derived from ancient submarine volcanoes of the Taranaki Basin, New Zealand, to address questions of sediment generation and transport from these volcanoes and their effects on basin geometry. Paleocurrent indicators and the distribution of high- and low-density turbidity current deposits suggest a fan system sourced from the north and oriented axially to an elongate basin, confined by the growing volcanic arc to the north and west and a fault-controlled topographic high to the east. Composition and sedimentary structures indicate that the majority of deposits in this area are reworked volcanic material, rather than primary deposits from individual eruption events. The near absence of pumice or other vesicular materials suggests that the volcanic eruptions were dominantly effusive rather than explosive, and were unlikely to have breached the sea surface. The high proportion of hypabyssal rock fragments in deposits suggests that sector collapse of volcanic flanks was an important sediment-generating mechanism. The Mohakatino Formation highlights the need for submarine volcanoes to be considered in source-to-sink investigations to ascertain their role as sediment sources to ocean basins, particularly in convergent margin settings where voluminous, caldera-forming rhyolitic eruptions can occur. The balance between autogenic and allogenic controls on sediment architecture may differ in deeply- and shallowly-submerged volcanoes, as the former are likely to be disconnected from some environmental signals such as sea level change. In both cases, the transfer zone between source and sink may be relatively short, increasing the likelihood that environmental and/or autogenic signals are transmitted to the sedimentary record. Understanding the role of submarine volcanoes in a source-to-sink framework lends valuable context to basin analysis and exploration efforts in settings where submarine volcanoes have contributed to the sedimentary record.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017