Contrasts in morphology and deformation offshore Montserrat: New insights from the SEA‐CALIPSO marine cruise data

Abstract

[1] During the December 2007, SEA-CALIPSO experiment we collected seismic reflection profiles offshore of Montserrat. Off the east coast, we imaged deep fans of volcaniclastic debris from three volcanoes progressively active from ∼2 Ma to present. Near-shelf sedimentation rates of 8-9 cm/ka are approximated following cessation of local volcanic activity. The fans were deposited on sediments with apparent dips towards the ESE-trending Montserrat-Havers fault system (MHFS) in southern Montserrat. The MHFS encloses the Soufrière Hills Volcano, has elevated crustal blocks at Roche's Bluff, St. Georges Hill, and Garibaldi Hill, and extends off the west coast. Off the west coast, the N-dip of two faults supports a N-dip interpretation for a major component of MHFS, the Belham Valley fault. We propose that local deformation is affected by stress redistributions consistent with a right-stepping, sinistral en-echelon fault system, but the interplay of transtension and magmatism has resulted in complex and evolving stress regimes.

Widespread and progressive seafloor-sediment failure following volcanic debris avalanche emplacement: Landslide dynamics and timing offshore Montserrat, Lesser Antilles

“…In addition, we use JC45/46 sidescan sonar data, swath bathymetry, chirp sub-bottom profiles and a three-dimensional (3D) seismic volume, as well as older 2D seismic profiles (vertical resolution >10 m) from the AGUADOMAR, CARAVAL and SEA-CALIPSO cruises (Deplus et al, 2001;Le Friant et al, 2004;Kenedi et al, 2010) (Fig. 5).…”

“…The latter strike NW-SE, or slightly oblique to the arc . Fault systems similar to the older, buried faults are well developed in the modern fore-arc (Feuillet et al, 2002Kenedi et al, 2010), accommodating trench-parallel extension due to the curved geometry of the plate boundary.…”

“…Both sub-units of Deposit 2 have a similar character: relatively high-amplitude curved or deformed reflections suggest a mix of volcanic blocks and seafloor sediment. The lower two sub-units of (Deplus et al, 2001;Le Friant et al, 2004;Kenedi et al, 2010). Line sections used in subsequent figs.…”

“…This work builds on previous geophysical investigations that have focussed on determining the local landslide deposit stratigraphy (Deplus et al, 2001;Le Friant et al, 2004;Kenedi et al, 2010;Lebas et al, 2011). The reader is referred to Lebas et al (2011) for an overview of the landslide deposit stratigraphy and parameters SE of Montserrat.…”

Chapter 1 An overview of the eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010

“…This can be accommodated by north -south extension of this part of the Caribbean plate (Lopez et al 2006). There is contemporary evidence for such extension from seismicity and geological evidence from roughly east -west normal faulting (Feuillet et al 2002(Feuillet et al , 2010Kenedi et al 2010). In particular, the WNW-trending Belham Valley Fault that crosses Montserrat adjacent to SHV forms part of a large transtensional fault system running NNW between Montserrat and Basse Terre, Guadeloupe -the Montserrat -Bouillante Fault System (Feuillet et al 2002).…”