Did South American Mixed Paleofloras evolve under thermal equability or in the absence of an effective Andean barrier during the Cenozoic?

Evidence of Neogene wildfires in central Chile: Charcoal records from the Navidad Formation

“…The current sclerophyllous flora of central Chile is derived from a Neogene Subtropical Paleoflora that through most of the Miocene occupied the central areas of Chile and Argentina, under a warm climate with high seasonal precipitation (Hinojosa and Villagrán, 2005;Hinojosa et al, 2011). Given such warm climatic conditions, with abundant vegetation growing during spring and becoming dry during summer, the landscape was probably highly fire-prone in the presence of an ignition source (e.g., see Pyne et al, 1996 andPausas andKeeley, 2009 for a general discussion on fire drivers).…”

“…Two fossil floras have been described at the bottom of the Navidad Formation, the first located in Los Goterones-Matanzas area (Troncoso, 1991;Troncoso and Romero, 1993;Hinojosa et al, 2015). Strontium dating on shell material yielded 87 Sr/ 86 Sr ages of 23 Ma at Goterones and 22.0-23.5 Ma at Matanzas (Hinojosa and Villagrán, 2005;Gutiérrez et al, 2009;Gutiérrez et al, 2013). They corresponded to Mixed Paleoflora (sensu Hinojosa and Villagrán, 1997), composed of Antarctic-Australasian and Neotropical elements.…”

“…Podocarpacae, Myrtaceae, Berberidaceae, and Nothofagus are the prevailing morphotaxa in such assemblages (Troncoso, 1991;Troncoso and Romero, 1993;Hinojosa et al, 2015). Palaeoclimate reconstructions from leaf physiognomic analyses (i.e., on the basis of leaf margin and size) indicate that such Mixed Paleofloras, grew under mesotherm climatic conditions, with mean annual temperatures between 15.6°C and 16.2°C, and annual precipitation between 762 and 1149 mm (data for Los Goterones and Matanzas, respectively; Hinojosa and Villagrán, 2005;Hinojosa et al, 2015). A second fossil flora was described at Boca Pupuya, biostratigraphically dated to the transition from Early to Middle Miocene (Troncoso, 1991;Troncoso and Romero, 1993;Encinas, 2006).…”

Reply to Comment of Encinas et al. (2014) on: ‘Evidence for an Early-Middle Miocene age of the Navidad Formation (central Chile): Paleontological, climatic and tectonic implications’ of Gutiérrez et al. (2013, Andean Geology 40 (1): 66-78).

“…Furthermore, although there may be no direct evidence of upwelling in the Navidad Formation itself, there are phosphate and diatom beds in the time-equivalent Coquimbo Formation at Tongoy and Carrizalillo to the north (Le Roux et al, 2005bRoux et al, , 2006. The precipitation of phosphate or diatom beds requires a long period of upwelling during which clastic sediments are not supplied to the outer continental shelf, which would have been unlikely during Navidad deposition given the humid climate at the time (Hinojosa and Villagrán, 2005;Gutiérrez et al, 2013).…”

Reply to Comment of Finger et al. (2013) on: ‘Evidence for an Early-Middle Miocene age of the Navidad Formation (central Chile): Paleontological, paleoclimatic and tectonic implications’ of Gutiérrez et al. (2013, Andean Geology 40 (1): 66-78)

“…In any case, given the now accepted Early to Middle Miocene age, this period was characterized by higher rainfall (Hinojosa, 2005;Hinojosa and Villagrán, 2005;Hinojosa et al, 2006;Gutiérrez, 2011;Gutiérrez et al, 2013), so that an increased sedimentation rate in the trench would have provided the necessary lubrication to prevent subduction erosion. The other possible causes for such a dramatic subsidence are mentioned and discarded by Encinas et al (2008) themselves: depression of the lower oceanic plate is ruled out by the very small size or absence of accretionary prisms along most of the Chilean margin; and crustal thinning and massive-scale sliding causing extension faulting is not supported by the presence of large faults in seismic profiles (Contardo et al, 2008;Fig.…”