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Geomorphologic and Stratigraphic Evidence of Ongoing Transpressional Deformation Across Lake Azuei (Haiti)
  • +9
  • Marie-Helene Cormier,
  • Kamal James,
  • Heather Sloan,
  • Trishna Ramsamooj,
  • Dominique Boisson,
  • Kelly Guerrier,
  • Casey Hearn,
  • John King,
  • Roberte Momplaisir,
  • Steeve Symithe,
  • Sophia Ulysse,
  • Nigel Wattrus
Marie-Helene Cormier
U. Rhode Island, Graduate School of Oceanography, Narragansett, RI, USA

Corresponding Author:milenecormier@gmail.com

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Kamal James
CUNY Brooklyn College, Brooklyn, NY, USA
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Heather Sloan
CUNY Lehman College, Bronx, NY, USA
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Trishna Ramsamooj
American Museum of Natural History, New York, NY, USA
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Dominique Boisson
State University of Haiti, Research Unit in Geosciences, Port-au-Prince, HaiY
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Kelly Guerrier
State University of Haiti, Research Unit in Geosciences, Port-au-Prince, HaiY
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Casey Hearn
U. Rhode Island, Graduate School of Oceanography, Narragansett, RI, USA
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John King
U. Rhode Island, Graduate School of Oceanography, NarraganseJ, RI, USA
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Roberte Momplaisir
State University of Haiti, Research Unit in Geosciences, Port-au-Prince, Haiti
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Steeve Symithe
State University of Haiti, Research Unit in Geosciences, Port-au-Prince, Haiti
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Sophia Ulysse
State University of Haiti, Research Unit in Geosciences, Port-au-Prince, Haiti
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Nigel Wattrus
U. Minnesota - Duluth, Duluth, MN, USA
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Abstract

he boundary between the North American and Caribbean plates cuts EW across the island of Hispaniola. Relative motion on this part of the plate boundary is transpressional and tectonic deformation is partitioned between a NW-SE fold-and-thrust belt and two E-W left-lateral faults 150 km apart. The southern fault, the Enriquillo-Plantain Garden Fault (EPGF), is well defined in western Haiti but looses its morphological expression as it nears Lake Azuei in eastern Haiti. Since the sedimentation rate is high for this 20 km-long lake, Holocene deformation should be recorded in its upper stratigraphy and bottom morphology. To test this hypothesis, we analyzed 200 km of subbottom (CHIRP) profiles collected in 2017 that imaged the upper 2 - 10 m of sediments. This dataset is complemented with other sonar data, including 140 km of echosounder profiles (Moknatian et al., Rem. Sensing 2017) and 65 km of CHIRP profiles (Wang et al., Tectonics 2018). Morphological and stratigraphic information extracted from the combined dataset are compiled into a detailed geological map, which reveals: 1) Gas-charged sediments occur across most of the flat lake floor. However, where the gas front is deeper, the CHIRP data show the rhythmic stratigraphy characteristic of turbidites; 2) Turbidite beds fold up along the edges of the lake floor, documenting the ongoing deformation of the basin margins; 3) In the southern part of the lake, en echelon folds are trending EW, a trend compatible with fault-propagation folds developing ahead of a S-dipping oblique-slip EPGF. We find no evidence of fault scarp or stratigraphic offset in that same area, as might be expected from a sub-vertical EPGF; 4) Deeper penetration seismic reflection profiles acquired concurrently with the CHIRP reveal that the west side of the lake is occupied by a NW-trending monoclinal fold, possibly the expression of a SW-dipping blind thrust fault at depth. Vertical faults across that monocline are associated with subtle breaks in slope. Careful mapping of these slope breaks shows that these faults strike NW-SE, subparallel to the monocline; 5) A < 2 kyr-old paleoshoreline is uplifted 1-2 m across the monocline and soft-sediment deformation suggestive of liquefaction also affects that area. A large earthquake on the presumed underlying blind thrust fault could explain these two features.