Palaeoecology of a Middle Miocene lake in China: preliminary interpretations based on phytoliths from the Shanwang Basin

• The lacustrine Early to Middle Miocene Shanwang Formation contains an exceptionally well preserved biota including insects, plants, and vertebrates that has been subject to intense study. Palaeoecological work on plant macrofossils and palynofloras indicate that the locality represents a forest under a humid, warm-temperate to subtropical climate that remained rather stable during the deposition of the formation. This interpretation is supported by fossil vertebrates such as bats and tapirs discovered in the Shanwang section. However, to date no information has been available on the presence, abundance, and taxonomic composition of grasses at this locality. Here, we report on phytoliths extracted from six samples from the Shanwang Formation, providing new evidence of the vegetation that grew around the lake. The phytolith assemblages contain well-preserved and abundant grass phytoliths, forest indicator phytoliths from dicotyledonous plants, and infrequent palm phytoliths. The grass phytoliths consist of forms produced by C,IC4 PACCAD grasses and pooids, with a minor component of morphotypes thought to derive from closed-habitat grasses. Our preliminary interpretation of these phytolith assemblages is that they reflect a lake-side wooded habitat and abundant helophytic to mesophytic grasses, with drier areas supporting pooid (and PACCAD) grasses. The data support the reconstruction of the Miocene Shanwang region as more humid and equable than presently. The Shanwang phytolith assemblages contrast with Miocene lacustrine phytolith assemblages from Turkey and the Great Plains of North America, which indicate grass communities characterized by diverse C3 pooids and different types of PACCAD grasses. Future research will determine whether this variability reflects large-scale biogeographic differences in grass communities or local, microclimate-related variation.

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NATURVETENSKAP  -- Biologi -- Botanik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Botany (hsv//eng)

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