Forearc crustal structure and controlling factors on basin formation across the southernmost Northern Andes
Geophysical and Geological Investigations
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The southernmost region of the Northern Andes was subject to the collision and accretion of the Caribbean Large Igneous Province (CLIP) during Late Cretaceous. A process that led to the entrapment of an oceanic crustal sliver, so-called “North Andean Sliver (NAS)”, conforming the underlying forearc basement. This study investigates the remnants of such collisional process throughout an integrated analysis of gravity, magnetic, seismic, and considerations from this and previous studies at the surface. The crustal model resulting from this work point towards evidence of a split paleo-island arc accreted almost undeformed to the continental margin and the residuum of a partial melting event. Furthermore, interpretation of the subsurface and 2D crustal forward model across the NAS’s southernmost boundary to the margin account for a tear fault system, very likely responsible for the east-north-eastward migration of the NAS. The trailing edge of the accreted sliver and its interaction with the continental margin indicate the development of a localized outer wedge (Santa Elena High), which may be in close relationship to a process of oblique subduction at a triple plate junction. The resulting configuration led to the development of two types of basins genetically related 1) a forearc s.s. depocenter controlled by the development of an outer forearc high, and 2) a transform boundary basin that records the periods of transtension and tectonic escape, both developed at least since the Oligocene. The results presented in this research work provide new insights into our understanding of early forearc configuration and further basin development following the accretion of oceanic terranes.
Består avAizprua, C., Witt, C., Brøner, M., Johansen, S.E., Barba, D., and Hernandez, M.J., (2020). Forearc Crustal Structure of Ecuador Revealed by Gravity and Aeromagnetic Anomalies and Their Geodynamic Implications, Lithosphere, 2020(1), pp. 1-23.
Aizprua, C., C. Witt, S. E. Johansen, and D. Barba (2019), Cenozoic stages of forearc evolution following the accretion of a sliver from the late Cretaceous-Caribbean Large Igneous Province: SW Ecuador-NW Peru, Tectonics, 38(4), 1441-1465.
C. Witt, J.Y. Reynaud, D. Barba, M. Poujol, C. Aizprua, M. Rivadeneira, C. Amberg (2019), From accretion to forearc basin initiation: The case of SW Ecuador, Northern Andes, Sedimentary Geology, 379, 138-157.