The Palynology of the Cerrejon Formation (Upper Paleocene) of Northern Colombia

Abstract

A palynological study of the Cerrejon Formation was conducted in order to date the formation and understand the floristic composition and diversity of a Paleocene tropical site. The Cerrejon Formation outcrops in the Cerrejon Coal Mine, the largest open cast coal mine in the world. Two cores (725 m) were provided by Carbones del Cerrejon LLC for study. Two hundred samples were prepared for palynology, and at least 150 palynomorphs were counted per sample where possible. Several statistical techniques including rarefaction, species accumulation curves, detrended correspondence analysis, and Anosim were used to analyze the floristic composition and diversity of the palynofloras. Palynomorph assemblages indicate that the age of the Cerrejon Formation and the overlying Tabaco Formation is Middle to Late Paleocene (ca. 60-58 Ma). Major structural repetitions were not found in the Cerrejon Formation in the Cerrejon coal mine, and there is little floral variation throughout. The floral composition, diversity, and lithofacies do not change significantly. Lithofacies associations and floral composition indicate deposition fluctuating from an estuarine-influenced coastal plain at the base to a fluvialinfluenced coastal plain at the top. There are, however, significant differences in the composition and diversity of coal and siliciclastic samples. Coal palynofloras have fewer morphospecies, and a distinct and more homogeneous floral assemblage compared to assemblages from the intervening sisliciclastic strata, suggesting that tropical swampy environments supported fewer plant species and had a distinct vegetation adapted to permanently wet environments.

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

“…Palaeotemperature estimates of 30-34 °C exceed MAT maxima of modern tropical forests 22 . However, the high rainfall estimates from the Cerrejon palaeoflora (~4m per year 11 ) combined with increased pco could have maintained forest floras under higher temperature conditions 23 .…”

“…Remains of Titanoboa were found in depositional environments consisting of coastal plains incised by large-scale river systems within a wet tropical rainforest 11 ' 2 " and were associated with an aquatic vertebrate fauna including podocnemidid pleurodire turtles, dyrosaurid mesoeucrocodylians, and elopomorph and dipnoan fishes. Similarities between depositional environments of the Cerrejon Formation and habitats of extant Eunectes together with inferred prey taxa (crocodyliforms) indicate a similar ecology of Titanoboa to modern anacondas 2 ' 3 .…”

Paleocene wind-dispersed fruits and seeds from Colombia and their implications for early Neotropical rainforests

“…9). D i s c u s s i o n. Aerofructus dillhoffii augments pollen and leaf data, indicating the presence of the Malvaceae in Paleocene Neotropical floras (Jaramillo et al 2007, Carvalho et al 2011. Leaves of Malvaciphyllum macondicus and abundant pollen grains of Bombacacidites annae found in the Cerrejón flora indicate the Paleocene occurrence of members of the Eumalvoideae and Bombacoideae clades respectively.…”

“…Three taxa from the Cerrejón Formation were collected from the middle and upper levels of a ca 700-m-thick stratigraphic sequence composed of abundant and thick coals, sandstones, and siltstones (Bayona et al 2008). The Cerrejón strata have been dated as middle-late Paleocene (ca 58-60 Ma) based on pollen zonation, correlations with stable carbon isotopic data, and marine microfossils (Jaramillo et al 2007.…”

“…Even though our fossil shows a greater similarity to species of Cavanillesia than to those of other genera, we take a conservative approach and place the fossil in a separate genus, due to marked differences in fruit size and the lack of its distinctive pollen grain in the Cerrejón palynoflora (Jaramillo et al 2007).…”