Major Neogene events of the Southeastern Pacific: the Chilean and Peruvian record
Abstract According to the biochronostratigraphic model proposed, the Neogene marine deposits in Chile and Peru represent two independent transgressive sequences (Alloformations), separated by a major regional hiatus. The earlier sequence, NSEPS-I, would stretch from the top of the Early Miocene up to the base of the Late Miocene (ca. 19-10 m.y. B.P. The upper sequence, NSEPS-II would correspond, in turn, to the Late Pliocene (ca. 3.5-1.6 m.y. B.P.). The regional hiatus separating both sequences would encompass the Late Miocene and the Early Pliocene (ca. 10-3.5 m.y. B.P.). The planktonic foraminiferal events described suggest an age of terminal Early Miocene-Middle Miocene and Late Pliocene, respectively. The paleoclimatic events recorded are three: a “Warming” Event lasting from the terminal Early Miocene to the end of the Middle Miocene (MMWE), 18-11.5 m.y. B.P.; a “Cooling” Event of the middle Late Pliocene (LPCE), 2.5±0.2 m.y. B.P.; and “Warming” Event spanning most of the Late Pliocene (LPWE), 3.5-2.2 m.y. B.P., restricted to the surface and intermediate sea waters of the middle and low latitudes. The last paleoclimatic event, not recorded as such so far, is both synchronous and mutually exclusive in latitudinal terms with the second one. Three tectonic regional events are analyzed: the Quechuan-1 Phase (19±1.5 m.y. B.P.); the Quechuan-2 Phase (10±1 m.y. B.P.); and the Geographic (=Rhodanian) Phase (3.5±0.5 m.y. B.P.). In the studied area there is no Late Miocene marine sedimentary record to confirm the terminal Tortonian or Quechuan-3 tectonic phase (ca. 7 m.y. B.P.), admitted to occur in the volcanoclastic continental sequences of northern Chile and southern Peru.