THE INFLUENCE OF ASEISMIC RIDGE SUBDUCTION IN THE SHAPING NORTHERN SOUTH AMERICA PACIFIC MARGIN: PRELIMINARY PROVENANCE PATTERNS OF THE CENOZOIC TUMACO FOREARC BASIN, SW COLOMBIA
Preliminary provenance analyses of the Tumaco forearc basin (onshore segment) in the Pacific region of southwestern Colombia have delineated the major sources and their tracer compositional assemblages.
The results have shown major shifts in detrital input, e.g., during the Miocene, an intermediate to felsic plutonic detrital source replaced the previous prominent volcano-sedimentary filling that characterized the basin. These provenance shifts are probably related to a major uplifting and exhumation phase of apparent deeper plutonic levels in the Western Cordillera that together with the associated structural segmentation record in the basin, are consequences of the subduction of some of the major aseismic ridges that characterized the Pacific margin of Northern South America. Additionally, the younger record in the Tumaco Basin was strongly controlled by the growth and enlargement of the Late Miocene to Pliocene magmatic arc in the Western Cordillera, which represents a renewed volcanic flux following the Early Oligocene magmatism, and may be also controlled by the subduction of the anomalous Cenozoic features of the converging Nazca plate (e.g. Carnegie ridge).
Ongoing stratigraphic and biostratigraphic analyses, together with higher resolution provenance and thermochronological approaches will allow understanding the influence that subduction of variable features of the Nazca oceanic plate had along the northern South America Pacific margin and their time-process relations.