Multiple tropical Andean glaciations during a period of late Pliocene warmth

Abstract

The extent and behaviour of glaciers during the mid-Piacenzian warm period illustrate the sensitivity of the cryosphere to atmospheric CO2 concentrations above pre-industrial levels. Knowledge of glaciation during this period is restricted to globally or regionally averaged records from marine sediments and to sparse terrestrial glacial deposits in mid-to-high latitudes. Here we expand the Pliocene glacial record to the tropics by reporting recurrent large-scale glaciation in the Bolivian Andes based on stratigraphic and paleomagnetic analysis of a 95-m sequence of glacial sediments underlying the 2.74-Ma Chijini Tuff. Paleosols and polarity reversals separate eight glacial diamictons, which we link to cold periods in the benthic oxygen isotope record. The glaciations appear to coincide with the earliest glacial activity at high northern latitudes and with events in Antarctica, including the strong M2 cold peak and terminal Pliocene climate deterioration. This concordance suggests inter-hemispheric climate linkages during the late Pliocene and requires that the Central Andes were at least as high in the late Pliocene as today. Our record fills a critical gap in knowledge of Earth systems during the globally warm mid-Piacenzian and suggests a possible driver of faunal migration preceding the large-scale biotic interchange in the Americas during the earliest Pleistocene.

Changes in ground deformation prior to and following a large urban landslide in La Paz, Bolivia, revealed by advanced InSAR

“…The overlying Cenozoic fill sequence comprises over 600 m of predominantly fine-grained lacustrine and fluvial sediments of the weakly lithified Miocene-Pliocene La Paz Formation. It coarsens upward and toward the cordillera into more competent late Pliocene and Early Pleistocene glacial and proglacial sediments (Roberts et al, 2018) that are up to 400 m thick. The fill has been offset by numerous faults trending northwest and west (Dobrovlny, 1962;Lavenu, 1978;Roberts et al, 2018) (Fig.…”

“…in the southern part of the city (Lavenu et al, 1989), and the 2.74 Ma Chijini Tuff (Roberts et al, 2017), which crops out along the west margin of the plateau (Dobrovolny, 1962) between 3800 and 3850 m a.s.l. The local Altiplano surface formed on top of the thick sequence of Pliocene-Pleistocene glacial sediments by 1.8 Ma or possibly as recently as 1.0 Ma (Roberts et al, 2018), attaining an elevation of approximately 4200 m a.s.l. in the vicinity of Pampahasi (Fig.…”

“…Ongoing fluvial downcutting and toe erosion by Río Irpavi help to maintain the slope's metastable state; spatiotemporal changes in fluvial erosion may have contributed to the differing pre-failure activity in the northern and southern parts of the landslide, as well as the increase in post-failure activity in both areas. This driver is a response to the 4 km drop in base level since the Early Pleistocene -from the time when the Altiplano plateau was internally draining to the present drainage to the Atlantic Ocean (Roberts et al, 2018) -and operates along other trunk streams in the basin.…”

Changes in ground deformation prior to and following a large urban landslide in La Paz, Bolivia revealed by advanced InSAR

“…CC BY 4.0 License. of the city (Lavenu et al, 1989), and the 2.74-Ma Chijini Tuff (Roberts et al, 2017), which crops out along the west margin of the plateau (Dobrovolny, 1962) between 3800 and 3850 m a.s.l. The local Altiplano surface formed atop the thick sequence of Plio-Pleistocene glacial sediments by 1.8 Ma or possibly as recently as 1.0 Ma (Roberts et al, 2018), attaining an elevation of approximately 4200 m a.s.l.…”

Effect of the Andean Geography and Climate on the Specialized Metabolism of Its Vegetation: The Subtribe Espeletiinae (Asteraceae) as a Case Example

“…The distribution of the páramo vegetation depends not only on the topography of the region but also on the Andean climate. With more than 20 known late Pliocene–Pleistocene glaciations during the last 3.5 million years, the past Andean climate was very dynamic [ 13 , 14 , 15 , 16 ]. During glacial maxima, the area of páramos was considerably larger than during the interglacial periods, promoting distributional changes of plant communities (both in elevation and latitude) as repeated events of expansion and contraction of the páramo zone took place [ 17 ].…”