Palaeoevironmental reconstruction based on palynomorphs from the upper Oligocene San Gregorio Formation (core LB1), in a semiarid coastal marine setting, Baja California Sur, Mexico
| Autor: | Elia Ramírez-Arriaga, Mercedes B. Prámparo, Enrique Martínez-Hernández, Javier Helenes-Escamilla |
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| Rok vydání: | 2021 |
| Předmět: |
Cloud forest
010506 paleontology geography geography.geographical_feature_category biology Ecology Dinoflagellate Paleontology Vegetation 010502 geochemistry & geophysics Oceanography Chaparral biology.organism_classification 01 natural sciences Diversity index Deciduous Species evenness Species richness Ecology Evolution Behavior and Systematics Geology 0105 earth and related environmental sciences Earth-Surface Processes |
| Zdroj: | Palaeogeography, Palaeoclimatology, Palaeoecology. 575:110476 |
| ISSN: | 0031-0182 |
| DOI: | 10.1016/j.palaeo.2021.110476 |
| Popis: | Terrestrial and marine palynomorph assemblages from a total of 42 productive samples from San Gregorio Formation core LB1 were analysed. Marine palynomorphs, such as dinocysts, acritarchs, copepod eggs, among others, dominated the associations. With regard to terrestrial palynomorphs, dicotyledonae (e.g. Anacardiaceae type, Chenopodipollis spp., Brossipollis spp., Euphorbiaceae type, Fabaceae type, Quercoidites sp., Polygonaceae type and Sterculiaceae type) were more abundant than monocotyledonae (e.g. Liliacidites spp. and Graminidites sp.). The recovered palynoflora gave evidence of two temperate highland communities: Pinus forest and cloud forest. Furthermore, representatives of the local semiarid vegetation (Brossipollis, Chenopodipollis, Ephedripites and Graminidites), growing throughout a palaeoaltitudinal gradient from the uplands down to the shoreline, such as chaparral, tropical deciduous forest, coastal grassland and coastal dune also occurred. Terrestrial taxa richness varied between 5 and 57, the diversity index ranged between 1.2 and 3, and evenness oscillated between 0.4 and 1. As for marine palynomorphs, the dominant dinoflagellate cysts were Cleistosphaeridium sp., Cordosphaeridium sp., Chiropteridium lobospinosum, Homotryblium sp., Hystrichokolpoma rigaudiae, Lingulodinium machaerophorum, Operculodinium centrocarpum, Polysphaeridium sp. and Spiniferites spp., suggesting that San Gregorio Formation core LB1 was deposited in a neritic marine environment. The dinocysts Chiropteridium lobospinosum and Tuberculodinium vancampoae support a late Oligocene age for the San Gregorio Formation at LB1. Marine taxa richness oscillated between 5 and 18, the diversity index ranged from 0.2 to 2.4 and evenness fluctuated between 0.1 and 0.9. CONISS statistical analysis of the terrestrial and marine palynomorphs allowed us to group the SGF assemblages into four palynozones. |
| Databáze: | OpenAIRE |
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