Studies in neotropical paleobotany. XV. A Mio-Pliocene palynoflora from the Eastern Cordillera, Bolivia: Implications for the uplift history of the Central Andes

Citation
A. Graham et al., Studies in neotropical paleobotany. XV. A Mio-Pliocene palynoflora from the Eastern Cordillera, Bolivia: Implications for the uplift history of the Central Andes, AM J BOTANY, 88(9), 2001, pp. 1545-1557
Citations number
60
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
AMERICAN JOURNAL OF BOTANY
ISSN journal
0002-9122 → ACNP
Volume
88
Issue
9
Year of publication
2001
Pages
1545 - 1557
Database
ISI
SICI code
0002-9122(200109)88:9<1545:SINPXA>2.0.ZU;2-V
Abstract
An assemblage of 33 fossil pollen and spores, recovered from the 3600-m hig h Pislepampa locality of E. W. Berry, Eastern Cordillera, Bolivia, adds con siderably to our knowledge of three aspects of the region in late Neogene t ime: (1) the paleovegetation, (2) the paleoclimate, and (3) the paleoelevat ion of the Central Andes. The plant microfossils recognized are Isoetes, Ly copodium (three types), Cnemidaria, Cyathea (three types), Grammitis, Hymen ophyllum, Pteris, trilete fern spores (two types), Danaea, monolete fern sp ores (four types), Podocarpus, Gramineae, Palmae, Ilex, cf. Oreopanax, Cava nillesia, cf. Pereskia, Compositae (three types), Ericaceae, Tetrorchidium, and unknowns (three types). The diversity of the Compositae suggest that t his flora has a maximum age around the Miocene-Pliocene boundary, that is, 6-7 million years. All members of the paleocommunity presently grow in the bosque montano humedo (cloud forest) along the eastern slope of the Central Andes of Bolivia, which occurs between MATs (mean annual temperatures) of similar to 10 degrees and 20 degreesC. The Pislepampa flora probably repres ents the lower limits of this forest because the fossil leaves collected by Berry from the same locality all have entire margins, suggesting that the flora grew near the cloud forest-tropical forest transition. Presently, the lower limit of the cloud forest forest has MATs of similar to 20 degreesC, a mean annual precipitation between 1000 and 1500 mm, and that part contai ning most of the identified genera of fossil pollen is found at elevations similar to 1200-1400 m. These conditions are thus inferred for the Pislepam pa flora; however, because of the uncertainty of the magnitude of global cl imate change and of possible changes in the ecological range of plant gener a, we estimate an error of at least +/- 1000 m for the paleoelevation estim ate. When the total uplift is corrected for probable amounts of erosionally driven isostatic rebound, the paleoelevation estimate suggests that from o ne-third to one-half of the uplift of the Eastern Cordillera had occurred b y the beginning of the Pliocene. This estimate is consistent with other pal eoelevation estimates from the Central Andes.