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Eocene vegetation and ecosystem fluctuations inferred from a high-resolution phytolith record

Lauren A. Miller, Selena Y. Smith, Nathan D. Sheldon and Caroline A. E. Stroemberg
Eocene vegetation and ecosystem fluctuations inferred from a high-resolution phytolith record
Geological Society of America Bulletin (June 2012) 124 (9-10): 1577-1589


A thorough understanding of the ecosystem factors that can act as drivers of vegetation change, an important factor for projecting impacts of future climate change, requires adequately distinguishing between plant community changes that occur on the local scale or over ecological time scales, and long-term trends. Phytolith assemblages have the potential to provide this information, but little work has been done so far to test their ability to do so in deep time. We examined vegetation patterns inferred from phytoliths (plant silica microfossils) from a single section of the Renova Formation, Timberhills region, Montana, dated to 39.2+ or -3 Ma (late middle Eocene). The section is composed of fluvial sediments overprinted by paleosols including Alfisols, Entisols, Inceptisols, and composite paleosols. Phytolith assemblages from 27 paleosol samples were used to reconstruct a high-resolution vegetation history for the area and were compared with paleosol data. Phytoliths are predominantly from forest plants and include tropical elements such as palms (Arecaceae) and gingers (Zingiberales), suggesting a paratropical forest. The high-resolution sampling records heterogeneous vegetation including shifts among closed forest, moderately open forest (forest gaps, edges, and woodland), and grass-dominated habitats. Grasses are interpreted as early open-habitat plants tolerant of drier conditions, but they appear to be replaced by forest vegetation with time, resulting in poor correspondence between paleosol type and phytolith assemblage at some stratigraphic levels, where paleosol morphology indicates a forest ecosystem and the phytolith assemblages indicate a changing grass-forest mixture as a function of depth within the profiles. This is the first study that has used phytoliths to construct a high-resolution record of vegetation from deep time, and we demonstrate that dense sampling and multiproxy approaches to paleoenvironmental reconstruction are necessary to capture vegetation heterogeneity in time and across microhabitats.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 124
Serial Issue: 9-10
Title: Eocene vegetation and ecosystem fluctuations inferred from a high-resolution phytolith record
Affiliation: University of Michigan, Department of Earth and Environmental Sciences, Ann Arbor, MI, United States
Pages: 1577-1589
Published: 20120621
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 105
Accession Number: 2012-065575
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2012247; accessed on July 2, 2012
Illustration Description: illus. incl. 1 plate, 3 tables, sketch map
Source Medium: WWW
N45°01'60" - N45°02'60", W112°16'00" - W112°15'00"
Secondary Affiliation: University of Washington, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201234
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