Abstract
Using bathymetric and multichannel seismic (MCS) data, we explored the volcanic influence on the bathymetric and stratigraphic features of the Mianhua Terrace. The Mianhua Terrace occupies the marine counterpart of the Northern Taiwan Volcanic Zone (NTVZ) along the collapsed Taiwan orogenic wedge and is dominated by post-collisional magmatism and extensional structures. The bathymetric data showed several semicircular-shaped features near the shelf break. The MCS profiles showed that the Pleistocene unconformity buried beneath the Mianhua Terrace is partly difficult to observe due to seafloor multiples, suggesting that the seafloor is dominated by physically hard lithology, probably volcanic lavas. We interpreted the high-amplitude reflectors and their projected seafloor relief as intrusive sills and associated extrusive edifice. Similarly, we interpreted high-amplitude reflectors in the vicinity of normal faults as intrusive sills emplaced and facilitated by fault structures. A volcanic or hydrothermal mound was also recognized. We propose that the Mianhua Terrace is a breached ramp in a transfer zone between the tips of two successive normal faults along the shelf break. Once the fault tips reactivate and extend toward each other, the Mianhua Terrace may continue to collapse, leading to catastrophic volcanic or associated hydrothermal events.
Highlights
Igneous and volcanic activities are commonly seen in post-collisional tectonic environments and are known as post-collisional magmatism [1,2,3,4]
Of a breached ramp in a transfer zone associated with the development of an extensional a model of a breached ramp in a transfer zone associated with the development of an normal fault system is proposed to explain the formation of the Mianhua Terrace
Using recently compiled bathymetric data and multichannel seismic (MCS) data, we present the stratigraphic, structural, and volcanic features in the Mianhua Terrance, offshore Northern Taiwan
Summary
Igneous and volcanic activities are commonly seen in post-collisional tectonic environments and are known as post-collisional magmatism [1,2,3,4]. Post-collisional structures postdate the cessation of the collision, probably due to the transfer of tectonic stress, and are generally characterized by extensional structures [5,6,7,8]. Concerning rock geochemistry, post-collisional magmatism generally occurs with specific geochemical patterns and spatiotemporal distribution. The geological structures of post-collisional magmatism are rarely geophysically imaged, and their structural features within the post-collisional framework are barely mentioned. Regional magmatism features the Northern Taiwan Volcanic Zone (NTVZ) dominated by post-collision magmatism, including inland Tatun, Kuanyin, and Keelung volcanic groups, and offshore volcanic Mianhua, Huaping, and Pengchia Islets (Figure 2) [14,15].
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