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Abstract Detail

The Miocene vegetation and environment of Western North America

Myers , Jeffrey Alan [1], Erwin, Diane Marie [2].

The Latest Miocene Anaverde Flora, Palmdale, CA (SoCA): The “Inland Empire” was Once a Really Nice Place to Live.

Over 1500 macrofossils, along with pollen, from six localities of the latest Miocene Anaverde flora (Palmdale, CA) document oak savanna vegetation that grew on the SoCA coastal slope before mountains blocked maritime climate.  Fossils, now housed at UCMP Berkeley, were salvaged during construction of the Antelope Valley Disposal Facility, and consist of fragmental material in mudstone drapes over gypsiferous, cross-stratified arkose in the fine-grained Upper Unit of the Anaverde Fm.  Seventeen taxa are tentatively recognized in the macroflora.  Dominants include poplar, willow, and sycamore in an association similar to that of modern cismontane SoCA bottomland vegetation.  Magnolia and “Persea” and abundant aquatic pollen reflect a climate with more summer moisture and a milder winter temperature than today.  Live oaks and sclerophyllous shrubs including Ceanothus precuneatus formed savanna woodland away from watercourses.  However, plants with tropical modern distributions originally recognized in the flora – some of which are known from older Miocene floras of the region - were misidentified, and the Anaverde flora reflects more temperate vegetation than the dry tropical woodland originally envisioned.  By the middle Miocene, intensification of the cold CA Current began to produce a summer-dry Mediterranean climate on the California coast.  Cold and drought intolerant plants common in middle Miocene floras of the region were gradually forced southward and coastward and replaced by a belt of oak woodland for much of the length of California by Anaverde time.  Later Pliocene uplift of the San Gabriel and San Bernardino Ranges isolated the Inland Empire from maritime influence to produce the arid creosote scrubland of today.

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1 - Western Oregon University, Earth Science, 345 N Monmouth Ave, Monmouth, OR, 97361, USA
2 - University of California, University of California Museum of Paleontology, 1101 Valley Life Science Building, UC Berkeley, Berkeley, CA, 94720, USA

Southern California
Late Miocene flora

Presentation Type: Symposium or Colloquium Presentation
Session: C2
Location: Salmon/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 5:00 PM
Number: C2015
Abstract ID:132
Candidate for Awards:None

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