Zircon U-Pb ages of super-units in the Coastal batholith, Peru: Implications for magmatic and tectonic processes

Stratigraphic framework of the late Miocene Pisco Formation at Cerro Los Quesos (Ica Desert, Peru)

“…The (East) Pisco Basin, in southern Peru, is the onshore sector of one of these basins. It is a 180 × 30 km elongated sedimentary basin bounded to the east by Mesozoic igneous rocks of the Coastal Batholith (Cobbing, 1999;Mukasa, 1986) and to the west by Precambrian to Jurassic metamorphic, igneous, and sedimentary rocks of the Coastal Cordillera, the onshore segment of the offshore Outer Shelf Ridge (Romero, Valencia, Alarcón, Peña, & Ramos, 2013 and references therein). The basin fill comprises, from the oldest to the youngest, the Eocene Caballas Formation and Paracas Group, the late Oligocene-middle Miocene Chilcatay Formation, and the middle Miocene-Pliocene Pisco Formation (DeVries, 1998;Dunbar, Marty, & Baker, 1990).…”

International Lateinamerika-Kolloquium 2009

“…Whereas the latter is nearly devoid of volcanic intercalations or detritus, the former includes volcaniclastic deposits as well as tuffs and lava flows (Callot et al, 2008). This sharp turning point in the stratigraphic record is dated at ~91-90 Ma (Callot et al, 2008) and coincides with the only significant uplift known in coastal southern Peru (Wipf, 2006), and with the emplacement, between 91 and 70 Ma, of the most voluminous units in the Coastal Batholith (Mukasa, 1986).…”

“…The conjunction of these quite anomalous thermal phenomena reflect a deep modification of the Pacific mantle convection and thus of subduction conditions along its margins. It is particularly striking that anomalous heating of the East Pacific lithosphere between ~91 and 70 Ma, as we infer here from independent sources, exactly coincided with emplacement of large plutonic volumes between 91 and 70 Ma in Peru (Mukasa, 1986). In order to determine preliminary block rotations and paleolatitudinal movements of the Panama volcanic arc, Late Cretaceous to Pleistocene tuffs, lavas and calcareous sandstones, were sampled in a total of 23 sites of five areas of Panama.…”

“…Available geochronologic data indicate that the Coastal Batholith was built by discrete plutonic pulses in the Early Jurassic, Late Jurassic, midCretaceous, and most of all Late Cretaceous-Paleocene, albeit with significant regional variations along strike (Mukasa, 1986;Clark et al, 1990). In particular, a significant pulse of pluton emplacement occurred at ~62-61 Ma along a >300 kmlong segment of the arc (Mukasa, 1986;Quang et al, 2003). This pulse and the major reactivation of volcanism at ~91 Ma coincided with major increases in accumulation rate in the backarc basin (Sempere et al, 1997;Callot et al, 2008), strongly suggesting that magmatic growth of the arc caused an orogenic development that was large enough to increase subsidence in the backarc, and thus to regionally flexure the lithosphere.…”

“…The batholith is composed of interpenetrating smaller tabular units, that are generally ~100-500 mthick each and display petrological gradations from mafic (dioritic to gabbroic), finer-grained facies near their bottom to felsic (granitic), coarser-grained facies near their top. Available geochronologic data indicate that the Coastal Batholith was built by discrete plutonic pulses in the Early Jurassic, Late Jurassic, midCretaceous, and most of all Late Cretaceous-Paleocene, albeit with significant regional variations along strike (Mukasa, 1986;Clark et al, 1990). In particular, a significant pulse of pluton emplacement occurred at ~62-61 Ma along a >300 kmlong segment of the arc (Mukasa, 1986;Quang et al, 2003).…”