Stratigraphy of Architectural Elements of a Buried Monogenetic Volcanic System

Abstract

Large volumes of magma emplaced and deposited within sedimentary basins can have an impact on the architecture and geological evolution of these basins. Over the last decade, continuous improvement in techniques such as seismic volcano-stratigraphy and 3D visualisation of igneous bodies has helped increase knowledge about the architecture of volcanic systems buried in sedimentary basins. Here, we present the complete architecture of the Maahunui Volcanic System (MVS), a middle Miocene monogenetic volcanic field now buried in the offshore Canterbury Basin, South Island of New Zealand. We show the location, geometry, size, and stratigraphic relationships between 25 main intrusive, extrusive and sedimentary architectural elements, in a comprehensive volcano-stratigraphic framework that explains the evolution of the MVS from emplacement to complete burial in the host sedimentary basin. The plumbing system of the MVS comprises saucer-shaped sills, dikes and sill swarms, minor stocks and laccoliths, and pre-eruptive strata deformed by intrusions. The eruptive and associated sedimentary architectural elements define the morphology of volcanoes in the MVS, which comprise deep-water equivalents of crater and cone-type volcanoes. After volcanism ceased, the process of degradation and burial of volcanic edifices formed sedimentary architectural elements such as inter-cone plains, epiclastic plumes, and canyons. Understanding the relationships between these diverse architectural elements allows us to reconstruct the complete architecture of the MVS, including its shallow (<3 km) plumbing system, the morphology of the volcanoes, and their impact in the host sedimentary basin during their burial. Insights from the architecture of the MVS can be used to explore for geoenergy resources such as oil, gas and geothermal energy in buried and active monogenetic volcanic systems elsewhere.

Identification and Characterization of a Buried Volcanic Field Using Seismic Reflection and Borehole Data

“…The second paper (Bischoff et al 2019a) is designed to present the 77 results of the seismic morphological and paleogeographic reconstruction of the MVF 78 area, in which we up-scale interpretations from the location of the Resolution-1 to a 79 regional scale. In the third paper (Bischoff et al 2019b), we unravel the complete 80 architecture of the MVF from emplacement to burial, characterizing its main intrusive, 81 eruptive, and sedimentary architectural elements, and their impact on geoenergy 82 resources such as hydrocarbons and geothermal energy. The knowledge of the "fossil" 83 volcanoes of MVF can provide useful insights of how volcanic fields form and evolve 84 elsewhere, including their perceived geological hazards, and potential to contain socio-85 economical resources.…”

Paleogeographic and Morphologic Reconstroction of a Buried Monogenetic Volcanic Field

“…Chronostratigraphic and isochron maps show that the 308 presence of the extinct submarine volcanic edifices had a local influence on the 309 distribution of sediments in the area(Figure 6 and 7b). Seismic imagery displays a 310 distinctive low-gradient setting occurring among cone-type edifices of the MVF, which 311 is interpreted as a low-energy sedimentary environment inBischoff (2019b). 312By 11 Ma, most volcanoes in the MVF were completely buried in a lower to 313 uppermost bathyal setting, with the exception of the pc14 and pc09, as both of these 314 volcanoes were partially buried and located in deeper waters (Figure 6b).…”