Stults, Debra , Axsmith, Brian .
Late Neogene Betulaceae of Alabama.
Representatives of Betulaceae occur mainly in cool temperate and boreal regions of North America, Europe, and Asia, and mountainous areas of Mexico and Central America. Currently important as timber resources, landscape ornamentals, and food (nuts of Corylus), the record of extant genera of Betulaceae in North America begins in the Eocene (Alnus, Betula, Carpinus, Corylus-like genus) and Oligocene (Ostrya). In 1916 Edward Berry described Betula prenigra from the Pliocene Citronelle Formation of the Gulf of Mexico Coastal Plain; however leaf venation and basal features were uncharacteristic of Betula nigra. Berry also described Betula nigra and Carpinus caroliniana from Alabama Pleistocene deposits. New investigation of Citronelle Formation sites in southwestern Alabama and an additional (possibly Pleistocene) site along the Mobile River yield fossils of Betulaceae. Shield-shaped leaves with evenly-placed, craspedodromous secondary veins and distinctively-serrated margins indicate that Betula nigra was part of the Mid-Pliocene Gulf Coast vegetation. Small, membranous-winged fruits and a 3-lobed catkin bract provide corroboration. Betula pollen has been recovered. Oblong/ovate leaves with craspedodromous secondaries, serrated margins, and acute/acuminate apices from the Citronelle Formation are suggestive of Carpinus or Ostrya. Characteristic nutlet bracts of Carpinus have been produced from the Citronelle Formation and the Mobile River site. A staminate catkin with typical Carpinus-like bracts and in situ pollen has been recovered from the Citronelle Formation. Evidence of Alnus consists of small numbers of pollen. Although 10 species of Betulaceae occur in the southeastern United States, only Alnus serrulata, Betula nigra, Carpinus caroliniana, and Ostrya virginiana frequent the Gulf of Mexico Coastal Plain. Our findings indicate Betula nigra, Carpinus caroliniana, and possibly Alnus and Ostrya were established in the area by Mid-Pliocene and persisted, probably due to regional climatic stability.
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1 - University of South Alabama, Department of Marine Sciences, Life Sciences Bldg 25, Mobile, Alabama, 36688, USA
2 - University of South Alabama, Biological Sciences, Life Sciences Bldg. #124, 307 University Blvd. North, Mobile, Alabama, 36688, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Williford A/Hilton
Date: Wednesday, July 11th, 2007
Time: 10:30 AM