ESTRATIGRAFÍA, PETROGRaFÍA Y ANÁLISIS MULTI-MÉTODO DE PROCEDENCIA DE LA FORMACIÓN GUINEALES, NORTE DE LA CORDILLERA OCCIDENTAL DE COLOMBIA

Transition From Collisional to Subduction‐Related Regimes: An Example From Neogene Panama‐Nazca‐South America Interactions

“…(~14 Ma). In this scenario, the youngest AHe age of 4.9 ± 0.6 Ma, which closely overlaps with the youngest AFT age population of 5.5 ± 2.6 Ma, is likely to represent the maximum accumulation age for the Guineales Fm., which is coherent with the previously suggested age < 9 Ma (Rodríguez et al, ). Nevertheless, further biostratigrpahic analysis and/or a larger amount of thermochronological ages will surely constrain more precisely the depositional age for the Guineales Fm.…”

“…The detrital nonreset character of the obtained AFT ages the Guineales Fm. is supported by as follows: (1) individual ages are mostly older than the maximum depositional age of 9 Ma previously suggested (Rodríguez et al, ) and (2) because individual ages closely resemble the AFT ages yielded by the Penderisco and Cruces Fm., which are potential sources for this sedimentary unit as discussed above in the sedimentary provenance section. Although this reasoning is more complicated when exploring the significance of the AHe individual due to the limited amount of analyzed grains, we interpret that this unit shows nonreset detrital AHe ages from the nearby sources because (1) the AHe dispersion observed in sample DMT‐010 cannot be explained by e [ U ] and grain size and (2) like the AFT analysis, individual AHe ages resemble those cooling ages obtained for samples UDB‐063 from the Penderisco Fm (~5–9 Ma) and DMT‐003 from the Cruces Fm.…”

“…are dominantly represented by clinopyroxene, suggesting the dominance of basic‐intermediate igneous sources. Previous geochemical and geochronological data (Rodríguez et al, ) indicate a rather mixed provenance including massive volcanic and porphyritic sources, as well as reworked sedimentary units. Their geochemical data show the presence of volcanic clasts with a shoshonitic signature similar to that described for rocks from the El Botón Basalts and related middle Miocene intrusives (Rodríguez & Zapata, ; Zapata & Rodríguez, ).…”

“…Sandstone beds within the Guineales Fm. have been previously described by Rodríguez et al () as wackes and litharenites, composed of lithic fragments of chert, andesite and mudstone, quartz and minor feldspar, pyroxene, hornblende, and biotite. Heavy minerals from sample DMT‐010 are represented by clinopyroxene, with minor hornblende, epidote, and zoisite (Figure d).…”

“…A maximum accumulation age of 9 Ma has been suggested for the Guineales Fm. based on a detrital zircon U‐Pb geochronological analysis (Rodríguez et al, ). Farther to the west, strata of the Atrato Basin overlying the volcanic basement of the Panama Arc consist of Oligocene to early Pliocene shallowing upward sequences that pass from deep to shallow marine and transitional conditions and which have been attributed to the occurrence of tectonic disturbances during the Neogene (Duque‐Caro, ).…”