First record of plant macrofossil from the Boa Vista Formation, Takutu Basin, Roraima State, Brazil

Abstract

Clayey intraclasts containing leaves preserved as impressions and compressions were collected from the Takutu River channel in the State of Roraima, Brazil. In the present study, 23 leaf fragments are described (morphologically and anatomically) and their taxonomic identity is proposed. These fossiliferous intraclasts were suggested in previous studies as coming from the Boa Vista Formation (Upper Pleistocene–Holocene). With the aim of finding new evidence to support this correlation, X-ray diffractometry (XRD) and Laser induced-breakdown spectroscopy (LIBS) analysis were performed, comparing the fossiliferous sample with two outcrops from the Boa Vista Formation. The results evidenced the chemical and mineralogical similarity between the fossiliferous intraclasts and both outcrops, suggesting their correlation with the Boa Vista Formation. Taxonomically, the specimens were recognized as fossil representatives of Dilleniaceae Salisb., Byrsonima Rich. ex Kunth (Malpighiaceae), Zanthoxylum L. (Rutaceae), and other six morphotypes. These taxa represent typical elements of the savanna (lavrados) of Roraima. The anatomical-cutillary characters of the mummified leaves indicate the dominance of xeromorphic plants, similar to the predominant woody species in the “lavrado” today, thus suggesting the same climatic-environmental conditions. Keywords: fossil leaves, leaf architecture, cuticular anatomy, angiosperm, Cenozoic.