Erwin, Diane M. , Bartley, Russell H. , Bartley, Sylvia E. , Springer, David J. .
A new paleoflora from the Miocene Middle Fork Eel River coal-bearing beds, Mendocino County, California, U.S.A.
A coal-bearing sequence exposed along the Middle Fork Eel River (MFER) near Covelo in California’s northern Coast Ranges provides new paleofloristic data for this once coastal region of California and corroborates the unit’s Miocene age. Clark in 1940 was the first to place the coal-bearing beds in their regional geologic context and assign them to the Miocene. This determination relied primarily on a Desmostylus molar found in shale overlying the coal and associated equivocal, though Miocene-compatible, marine mollusks. The MFER coal-bearing beds are often referred to the Temblor Formation; however, this assignment goes against modern-day stratigraphic protocols and therefore we use the informal name Sand Bank beds (SBb) here in referring to this unit. Stratigraphy and sedimentology of the SBb show it represents a fluvial-floodplain/deltaic-mire-estuarine-marine sequence. The fluvial system originated from an upland region to the north and flowed south where it fed a near coastal swampy forested bottomland (mire). Initial analysis of plant fossils from the shale and mudstones associated with the main MFER coal outcrop shows swamp cypress Taxodium-like trees were among the dominants, as represented by compressed foliage from shale overlying the coal, Taxodioxylon wood from the coal, and abundant taxodiaceous pollen from the underclay beneath the coal. The underclay palynomorph assemblage also includes lycophytes, abundant ferns similar to Polypodiaceae, Gleicheniaceae, cf. Osmundaceae, and cf. Schizaeaceae; conifers with affinities to Pinaceae (e.g. Pinus, Picea, Pseudotsuga/Larix,?Abies), Cupressaceae, and Podocarpaceae; and other herbaceous and woody angiosperms (e.g. Asteraceae, Chenopodiaceae/Amaranthaceae, Graminae, Sparganiaceae/Typhaceae, Betulaceae, Cornaceae?, Ericaceae, Fagaceae, Ilex, Juglandaceae (Carya, Juglans, Pterocarya, ?Cyclocarya), Leguminosae, Hamamelidaceae (Liquidambar), Onagraceae, Rhamnaceae?, Salicaceae, Tiliaceae, and Ulmaceae). The SBb palynoflora shares a high floristic correspondence with the assemblages from the early to middle Miocene Weaverville flora of northern California and the middle to late Homerian flora from the Kenai Peninsula, Alaska.
Log in to add this item to your schedule
1 - University of California, Museum of Paleontology, 1101 Valley Life Sciences Building, Berkeley, CA, 94720, USA
2 - Mendocino County Museum, 400 E. Commercial Street, Willits, CA, 95490
3 - Noyo Hill House, 28953 Highway 20, Fort Bragg, CA, 95437, United States
4 - College of the Redwoods–Mendocino Coast, Geology, 1211 Del Mar Drive, Fort Bragg, CA, 95437, United States
Northern Coast Ranges
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM