Late Paleocene leaf macroflora from a destroyed outcrop of the Marcelina Formation, Paso Diablo Mine, Venezuela: a rescue record

Carlos E. Solano Nava 

In 2016, a production blast at a mining face of the Paso Diablo Mine (Guasare Basin, northwestern Venezuela) exposed a level rich in fossil leaves of the Marcelina Formation (late Paleocene), located between coal seams 4O and 4M. The material was removed as overburden by a mining shovel a few hours after it was documented. We present the first published record of leaf macroflora from this formation at the mine, based on 25 blocks recovered from the blast debris (27 leaves or fragments) and 8 photographic records of unrecovered specimens documented at the mine face. The leaves are preserved in two facies: carbonaceous shales with leaves accumulated as leaf litter, and massive sandstones with scattered leaves and woody debris. These facies are interpreted as recording a low-energy swamp plain interrupted by a higher-energy event that rapidly buried the leaf litter, between two long-lived peat-forming episodes. Six informal morphotypes are recognized on the basis of leaf architecture, without assignment to family. Elliptic pinnate leaves predominate, followed by broad leaves with numerous straight, parallel secondary veins; a leaf with palmate venation, a small lamina, a leaf with ascending secondaries and monocot remains are also recorded. All laminae with an observable margin are entire. Some leaves show perforations, marginal notches and areas lacking the carbonaceous film that are compatible with insect damage, although they could also result from the blast or from diagenetic processes. The paleoflora is consistent with that of the Cerrejón Formation, ~43 km away on the other side of the Sierra de Perijá, and a resemblance of the broad leaves to Menispermites guajiraensis, limited to the pattern of the secondary veins, is proposed as a hypothesis. Photographs and specimen metadata are available on Zenodo.