Parrott, Joan , Estrada-Ruiz, Emilio , Thompson, Dori , Upchurch, Garland , Wheeler, Elisabeth , Mack, Greg .
The conifer wood flora of the Upper Cretaceous Jose Creek Member, McRae Formation, south-central New Mexico: A preliminary report.
The Jose Creek Member of the McRae Formation in south-central New Mexico yields a significant flora of Maastrichtian age located 200 km or more from the paleo-coastline. Leaf impressions are the best known remains from the Jose Creek flora, but significant numbers of conifer and angiosperm woods have been discovered recently. Conifers comprise the majority of woods and are known as in situ stumps, logs, and pieces of float. At least eight distinct conifer morphotypes are present from fewer than twenty thin-sectioned specimens. Two morphotypes have araucarioid intertracheary pitting, a feature found in Araucariaceae and Cheirolepidiaceae. One has up to 5-seriate intertracheary pitting and araucarioid cross field pitting with up to 15 or more pits per cross field. At one locality this wood is associated with impressions of Brachyphyllum macrocarpum, Araucarites longifolius, and Dammarites, taxa assigned to Araucariaceae. The largest wood is a taxodioid conifer known from an in situ stump 1.5 m in diameter. This wood is characterized by abundant bi- and triseriate rays, septate tracheids, and cross field pitting with 1 to 2 (rarely 3) pits per field. This conifer is known in association with shoot impressions of an extinct redwood. The remaining wood types have a suite of characteristics found in extant Cupressaceae/Podocarpaceae. These include uniseriate to opposite biseriate intertracheary pitting, axial parenchyma, predominantly uniseriate rays, and taxodioid or cupressoid cross field pitting. The Jose Creek conifer woods occur at coeval localities in the southern Western Interior of North America, supporting evidence from angiosperm woods for a shared flora during the latest Cretaceous. At least half of the conifer wood morphotypes have no annual rings, reinforcing evidence from leaf macrofossils and angiosperm woods for a warm subtropical to paratropical climate with minimal freezing. Conifer wood groups that are restricted to either coastal or interior environments in BigBend, Texas, occur together in the Jose Creek wood flora. This may be due to the combination, in the Jose Creek Member, of a humid to wet climate and an abundance of well-drained soils, which are spatially segregated in Big Bend, Texas.
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1 - 207 Pioneer Trail, San Marcos, TX, USA
2 - Texas State University, Department Of Biology, 601 University Drive, San Marcos, TX, 78666, USA
3 - 1508 Mockingbird Dr, San Marcos, TX, 78666, USA
4 - DEPT OF WOOD & PAPER SCIENCE, 710 Dixie Trail, Raleigh, NC, 27607, USA
5 - New Mexico State University, Department of Geological Sciences, Las Cruces, NM, 88003, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union A/Hyatt
Date: Wednesday, July 11th, 2012
Time: 8:30 AM