Abstract
The southernmost portion of the Liquiñe-Ofqui fault zone (LOFZ) lies within the proposed slab window which formed due to oblique subduction of the Chile Ridge in Patagonia. Mapping of paleo-surface ruptures, offsets, and lithological separations along the master fault allowed us to constrain geologic slip rates for the first time with dextral rates of 11.6–24.6 mm/year (Quaternary) and 3.6–18.9 mm/year (Late-Cenozoic) respectively. We had trouble mapping the LOFZ in one local because of a partially collapsed and previously undiscovered volcanic complex, Volcan Mate Grande (VMG: 1,280 m high and thus Vesuvius-sized) that grew in a caldera also offset along the LOFZ and has distinct geochemistry from adjacent stratovolcanoes. Besides the clear seismic and volcanic hazard implications, the structural connection along the main trace of the fast slipping LOFZ and geochemistry of VMG provides evidence for the slab window and insight into interplay between fast-slipping crustal intra-arc crustal faults and volcanoes.
Highlights
The southernmost portion of the Liquiñe-Ofqui fault zone (LOFZ) lies within the proposed slab window which formed due to oblique subduction of the Chile Ridge in Patagonia
Analysis of submarine data after the 2007 event suggested that the main trace of the LOFZ did not rupture to the seafloor, and with subtle evidence, which in places is obscured by submarine landslides, to suggest instead that seafloor rupturing occurred along a minor fault parallel to the main L OFZ25
There are at least 30 Holoceneactive Southern Volcanic Zone (SVZ) volcanoes located within or near the southernmost 400 km of the LOFZ (Figs. 1, 2, 328). This area was completely covered by the Patagonian Ice Sheet during the Last Glacial Maximum ( LGM29) at 27–25 ka with initial deglaciation after 18–17 ka, and the Younger Dryas glacial advance from 12.9 to 11.7 ka[30]
Summary
The southernmost portion of the Liquiñe-Ofqui fault zone (LOFZ) lies within the proposed slab window which formed due to oblique subduction of the Chile Ridge in Patagonia. Long-term Cenozoic geologic and structural evidence suggests rapid motion along the LOFZ (e.g.17,18), in the 35 years since Forsythe and N elson[11] postulated that the Chiloe Block is moving northward relative to South America along the LOFZ due to oblique convergence or to forces in response to ridge subduction, there are still no direct measurements or field-derived estimates of strike slip slip rates. 50°S migration of heat and fluids (including the formation of volcanoes), there are as of yet no documented dextral Quaternary strike slip slip-rate estimates derived from geological or geomorphic evidence to confirm this activity or constrain how fast this takes place along the LOFZ This is primarily due to the challenging access, overprinting by young volcanic and glacial cover and erosion, fiords, and dense temperate rainforest maintained by high annual rainfall (2 to 5 m/year). This study aims to obtain first order field-derived Late-Cenozoic and Late-Quaternary strike slip, dextral slip rates along the master fault of the LOFZ through a Scientific Reports | (2021) 11:7069 |
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