Constraints on the paleoelevation history of the Eastern Cordillera of Colombia from its palynological record

Abstract

We attempted to make an objective assessment of whether fossil pollen assemblages from the Sabana de Bogotá require surface uplift of ~2000 m since 6–3 Ma, as has been argued. We relied on recently published elevation ranges of plants for which fossil pollen has been found in sites 2000–2500 m high in the Sabana de Bogotá. The elevation ranges of fossil plants do not overlap, suggesting that those ranges may be too narrow. By weighting these elevation ranges by percentages of corresponding fossil pollen and summing them, we estimated probability density functions for past elevations. These probability distributions of past elevations overlap present-day elevations and therefore do not require surface uplift since deposition of the pollen. Fossil pollen assemblages include pollen from some plant taxa for which we do not know present-day elevation ranges, and therefore, with a more complete knowledge of elevation distributions, tighter constraints on elevations should be obtainable. The elevation of the oldest assemblage, from Tequendama, which lies at the southern edge of the Sabana de Bogotá and is thought to date from 16 to 6 Ma, is least well constrained. Although our analysis permits no change in elevation since the pollen was deposited, we consider 1000–2000 m of elevation gain since 15 Ma to be likely and consistent with an outward growth of the Eastern Cordillera.

Peer Review #4 of "Synthesis of geological data and comparative phylogeography of lowland tetrapods suggests recent dispersal through lowland portals crossing the Eastern Andean Cordillera (v0.2)"

“…Biologists comparing molecular phylogenetic dating of a given clade to historical models of orogeny also need to make assumptions about when during the process of uplift did migration end. In the case of the EC-MA one could assume the age of initial uplift of roughly 20 million years ago (Ma) for the separation of an ancestral population, or perhaps the final uplift age of 5-2 Ma based on palynological records near Bogotá in the middle of the EC (Van der Hammen et al,1973;Hooghiemstra et al, 2006), or an intermediate age (for a revised palynological interpretation see Molnar and Pérez-Angel [2021]). With such a long time period between the start and end of uplift of the EC-MA, this process could explain nearly any divergence date investigators might obtain from evolutionary genetic analysis of their taxon of interest.…”

“…This paleoelevation figure was derived from palynological changes, which then were converted to temperature ranges (~9-12 °C, [Hooghiemstra et al, 2006]), and then to a corresponding elevation change (~2000 m) according to estimated lapse rates. Published elevation ranges of modern plants, however, may be shown to overlap the paleobotanically derived flora, requiring no elevation change (Molnar and Pérez-Angel, 2021). Independently derived paleotemperatures from biomarkers also suggest that the estimated changes in temperature may need to be revised downwards (3 ± 1 °C, Anderson et al, 2015).…”

Synthesis of geological data and comparative phylogeography of lowland tetrapods suggests recent dispersal through lowland portals crossing the Eastern Andean Cordillera

“…Biologists comparing molecular phylogenetic dating of a given clade to historical models of orogeny also need to make assumptions about when during the process of uplift did migration end. In the case of the EC-MA one could assume the age of initial uplift of roughly 20 million years ago (Ma) for the separation of an ancestral population, or perhaps the final uplift age of 5–2 Ma based on palynological records near Bogotá in the middle of the EC ( van der Hammen, Werner & van Dommelen, 1973 ; Hooghiemstra, Wijninga & Cleef, 2006 ), or an intermediate age (for a revised palynological interpretation see Molnar & Pérez-Angel (2021) ). With such a long time period between the start and end of uplift of the EC-MA, this process could explain nearly any divergence date investigators might obtain from evolutionary genetic analysis of their taxon of interest.…”

“… Stippled areas in the figure represent sedimentary environments interpreted from preserved rock sequences; numbers indicate the stratigraphic sequence where it is preserved (1: Grosse, 1926 ; 2: Parnaud et al, 1995 ; Erikson et al, 2012 ; 3: Guerrero, 1997 ; Montes et al, 2021 ; 4: Gómez et al, 2005 ; 5: Montes et al, 2010 ; 6: Quiroz et al, 2010 ; 7: Borrero et al, 2012 ; 8: Barat et al, 2014 ; 9: van der Hammen, Werner & van Dommelen, 1973 ; Molnar & Pérez-Angel, 2021 ; 10: Echeverri et al, 2015 ; Gallego-Ríos et al, 2020 (10); Weber et al, 2020 ; 11: Moreno et al, 2015 ; 12: Farris et al, 2017 ; 13: Jaramillo et al, 2017 ; Hoorn et al, 2022 ; 14: León et al, 2018 ). Most clastic deposits at this time are fluvial sands and near-shore environments, and mark the segmentation of basins by rising mountain belts and northward-propagating magmatic belts.…”

“…This paleoelevation figure was derived from palynological changes, which then were converted to temperature ranges (~9–12 °C, ( Hooghiemstra, Wijninga & Cleef, 2006 )), and then to a corresponding elevation change (~2,000 m) according to estimated lapse rates. Published elevation ranges of modern plants, however, may be shown to overlap the paleobotanically derived flora, requiring no elevation change ( Molnar & Pérez-Angel, 2021 ). Independently derived paleotemperatures from biomarkers also suggest that the estimated changes in temperature may need to be revised downwards (3 ± 1 °C, Anderson et al, 2015 ).…”