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  • 1
    Publication Date: 2018-12-14
    Description: Highlights • Northern Hispaniola Margin is studied with new high-resolution bathymetry and vintage seismic data. • Northern Hispaniola Deformed Belt forms an active N-verging fold-and-thrust imbricate system. • Gravity failures are frequent features in the Northern Hispaniola Margin and Bahamas Banks slope. • Oblique collision accelerates the Bahamas Carbonate Province collapse and retreat. • New observations help the assessment of tsunami hazards in the Northern Caribbean region. Abstract The northern margin of Hispaniola records the oblique collision/underthrusting of the Bahamas Carbonate Province with the island-arc. Due to the collision, northern Hispaniola has suffered several natural disasters caused by major earthquakes and tsunamis, such as the historic earthquake of 1842, the tsunami caused by earthquake-driven slumping in 1918 in the Mona Passage, the seismic crisis of 1943–1953 with five events of M 〉 7.0 or the seismic crisis of 2003 with a main shock of M6.3 and a large aftershock of M5.3. Using new swath multibeam bathymetry data and vintage single- and multi-channel seismic profiles, we have performed a regional scale analysis and interpretation of the shallow surface and active processes along the northern margin of the Dominican Republic. We have identified three morphostructural provinces: a) the Bahamas Banks, b) the Hispaniola Trench and c) the Insular Margin, which are divided into two tectonic domains, the Collision Domain and Underthrusting Domain. The southern slope of the Bahamas Carbonate Province shows a very irregular morphology produced by active erosive processes and normal dip-slip faulting, evidence of an extensional tectonic regime and margin collapse. This collapse is of major extent in the Oblique Collision Domain where there are erosive and fault escarpments with higher dip-slip fault throws. The Hispaniola Trench, is formed by the Caicos and Hispaniola basins in the underthrusting domain, and by the Santisima Trinidad and Navidad basins in the Oblique Collision Domain. They have a flat seafloor with a sedimentary filling of variable thickness consisting of horizontal or sub-horizontal turbiditic levels. The turbiditic fill mostly proceeds from the island arc through wide channels and canyons, which transports sediment from the shelf and upper slope. The Insular Margin comprises the Insular Shelf and the Insular Slope. The active processes are generated on the Insular Slope where the Northern Hispaniola Deformed Belt is developed. This Deformed Belt shows a very irregular morphology, with a WNW-ESE trending N verging imbricate thrust-and fold system. This system is the result of the adjustment of the oblique collision/underthrusting between the North American plate and the Caribbean plate. In the Oblique Underthrusting Domain the along-strike development of the imbricate system is highly variable forming salients and recesses. This variability is due to along-strike changes in the sediment thickness of the Hispaniola Trench, as well as to the variable topography of the underthrusting Bahamas Carbonate Province. In the Oblique Collision Domain, the morphology of the Insular Slope and the development of the Deformed Belt deeply change. The imbricate system is barely inferred and lies upslope. These changes are due to the active collision of Bahamas Carbonate Province with the Insular Margin where the spurs are indented against the Insular Margin. Throughout the entire area studied, gravitational instabilities have been observed, especially on the Insular Margin and to a lesser extent on the southern slope of the Bahamas Carbonate Province. These instabilities are a direct consequence of the active underthrusting/collision process. We have mapped large individual slumps north of Puerto Plata in the Oblique Underthrusting Domain and zones of major slumps in the Oblique Collision Domain. These evidences of active processes must be considered as near-field sources in future studies on the assessment of tsunami hazards in the region.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2014-10-07
    Description: The eighteenth/nineteenth century ‘craters of elevation’ theory required magma to uplift strata, doming the surface and creating a central down-fallen ‘crater’ or graben. Exponents of craters of elevation attempted to apply it to explain the origin of all volcanoes, and rapidly the contemporary competing ‘craters of eruption’ theory replaced it as the paradigm for volcano construction. Several historic examples have shown that intrusions can cause uplift, termed bulges and can create features like those proposed for craters of elevation (e.g. at Usu 1944, Bezymianny 1955 and Mt. St. Helens 1980). Work on sedimentary basins that have had igneous activity has shown that intrusions create ‘forced folds’ that uplift and deform strata in a similar way to that originally proposed for craters of elevation. In view of the above, we investigate large-scale intrusion-related topographic changes at two sites where the craters of elevation theory was developed: the monogenetic volcanoes of the Chaîne des Puys, France and the Teide stratovolcano, Tenerife. We combine observations of such features with examples of forced folding to integrate the two fields of research. Our observations in the Chaîne des Puys show that: (1) the Petit Puy de Dôme has a bulge of up to 150-m uplift. The uplift has a central depressed area (a graben), a dense network of normal faults, basal thrusts and an aborted landslide. (2) The Grosmanaux volcano is a forced fold created by uplift of a previously flat-lying area, and has dense faulting and a graben on the resultant topographic bulge. It was the site also of a major vulcanian eruption from the associated Kilian crater. (3) The Gouttes volcano was uplifted by an intrusion like the Petit Puy de Dôme, but then collapsed to generate a landslide and lateral blast. (4) Excavation in the Lemptégy Volcano exposes intra-eruption intrusions with associated uplift, providing examples in cross-section of the internal deformation likely to be found inside other Chaîne des Puys uplifted bulges. On Teide, a bulge near the summit shows similar structures and surface tilting as seen on the Petit Puy de Dôme and this bulging may have formed during the eruption of the Lavas Negras, the most recent activity on the summit area. Fault scarps on Teide also expose small cryptodomes, like those seen at Lemptégy. These examples, coupled with field studies on eroded intrusions, data on forced folds in basins and analogue models, show how large-scale topographic remodelling and structural change can be created by intrusions. These can rapidly and significantly change the volcanic edifice. A crater of elevation bulge, or forced fold that is stabilised by the cooling of the intrusion, will remain an important structural element in a volcano. This process starts even at the small scale of monogenetic volcanoes, and could occur through the lifetime of any growing stratovolcano. Such activity may be commonplace, but may be masked by concomitant eruption or removed by subsequent collapse. Monitoring and hazard strategies should be ready to deal with such large-scale events that will seriously modify the eruptive activity and stability of a volcano within days or weeks. ©2014 Springer-Verlag Berlin Heidelberg
    Print ISSN: 0258-8900
    Electronic ISSN: 1432-0819
    Topics: Geosciences
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  • 3
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