Preliminary palynostratigraphic results of Tehuacan Formation (upper Oligocene-middle Miocene)from Puebla State, Mexico

RAMIREZ-ARRIAGA, E.; MARTINEZ-HERNANDEZ, E.; PRAMPARO, M. B.; MACIAS ROMO, C.; NIETO SAMANIEGO, F.; VALIENTE -BAUNET, ALFONSO; DAVALOS-ALVAREZ,O.G.

Bonn, Alemania

Congreso; XIIInternational Palynological Congress-/VIII International Organisation of Palaeobotany; 2008

IPC and IOPC

Preliminary palynostratigraphic results of Tehuacan Formation (late Oligocene – Middle Miocene) from Puebla State, Mexico. Ramírez-Arriaga, E.1, Martínez-Hernández, E. 1, Prámparo, M. B.2, Macías-Romo, C. 1, Nieto-Samaniego, A.F.3 and Dávalos-Álvarez, O.G 1Laboratorio de Palinología,  Instituto de Geología, Universidad Nacional Autónoma de México, Distrito Federal, México. 2Unidad de Paleopalinología, IANIGLA-CCT CONICET, Mendoza, Argentina. 3Centro de Geociencias, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México. Palynostratigraphic researches carried out at a continental basins of central Mexico has allowed the reconstruction of local and regional Cenozoic communities as well as the climatic conditions during Late Eocene – Early Oligocene (Martínez-Hernández and Ramírez-Arriaga, 2006; Ramírez-Arriaga et al., 2006). Nevertheless, there are other Cenozoic geological units such as the Tehuacan Formation that had not been studied yet and whose study is providing important information on Paleogene and Neogene vegetations. Ages previously reported for the Tehuacan Formation indicate a deposition interval from Late Oligocene to Early Miocene  (27.1 ± 0.7 to 16.4 ± 0.5 My). This formation has hererogeneus lithology that varies from conglomerates to siltstones as well as evaporites (Dávalos-Álvarez, 2006). The current research provides the preliminary results of  palynological analysis of an evaporitic section corresponding to the upper part of Tehuacan Formation that  has been recently dated as Middle Miocene (15.6 ± 0.4 My). The palynological assemblages show the existence of different plant communities. The middle Miocene regional vegetation was characterized by Pinus and Quercus forest as well as cloud forest with Liquidambar, Alnus, different species of Engelhardtia and fern spores. However, other palynological associations include several species of cacti reported for the first time, suggesting that local communities were adapted to semiarid conditions. Moreover, fossil pollen grains belonging to the low deciduous forest as Bursera, Caesalpinia, Acacia and different types of Leguminosae, as well as those dominated by rossete-plant communities such as Yucca. Our results indicate that most plant communities that are growing nowadays in Tehuacan valley seem to be established in this area of Mexico since the Miocene.