Abstract Detail

Campanian-Maastrichtian floras on Laramidia: vegetation trends west of the seaway

Parrott, Joan [1], Upchurch, Jr., Garland [2].

The Angiosperm Wood Flora of the Upper Cretaceous (Campanian) McRae Formation, South-Central New Mexico: Diversity and Significance .

The Jose Creek Member of the McRae Formation, south-central New Mexico, preserves a diverse angiosperm flora of Late Campanian age (74–76 Ma). The Jose Creek Member is of special interest because it provides an abundance of fossil evidence in the form of leaves, reproductive structures, and silicified woods found in situ and as float. The Jose Creek wood flora, as currently understood, is one of the three most diverse Cretaceous wood floras in the world, and the only one where the majority of wood types represent mature, rather than juvenile, wood. Thirty-six species of non-monocot angiosperms are present and represent both members of the magnoliid clade and eudicots. Most magnoliids represent Lauraceae (nine wood types). Today the family is a dominant element in Asian tropical and subtropical vegetation. Four wide-rayed platanoid types have a combination of features considered primitive in the Baileyan scheme of advancement (e.g., exclusively solitary vessels, scalariform perforation plates and very indistinct or no growth boundaries), warranting a new genus. Twenty-four woods (67 %) have simple perforation plates. An assemblage of exceptionally large angiosperms (Forest of Giants) consisting of in situ stumps and logs is composed of three wood types: Paraphyllanthoxylon, a probable Lauraceae, and a third morphotype with simple perforation plates and axial parenchyma in short rows. The largest Cretaceous angiosperm stump yet recorded worldwide, a Paraphyllanthoxylon encased in a matrix of coarse sandstone, measures two meters in diameter, indicating long periods of stable environment interrupted by high-energy disturbances. The absence of conifers at the site confirms evidence from Big Bend for angiosperm tree dominance in some ecological settings at lower-middle latitudes by the Late Campanian. A comparison of the Jose Creek wood flora to fossil woods worldwide indicates heterogeneity in the evolution of wood anatomical features. A higher percentage of McRae woods have solitary vessel arrangement compared to woods from Late Cretaceous or Paleocene floras worldwide, indicating a “less modern” aspect to the McRae flora in terms of that character, as would be expected given their Late Campanian age. In contrast, the percentage of taxa with simple perforation plates and obvious axial parenchyma shows Jose Creek woods to be more “modern” than the global average for Maastrichtian and Paleocene woods, and intermediate between these woods and woods of the Deccan Intertrappan Series (67-64 Ma, latest Cretaceous to earliest Paleocene).

1 - Texas State University, Department of Biology, 601 University Drive, San Marcos, TX, 78666
2 - Texas State University, Department Of Biology, 601 University Drive, San Marcos, TX, 78666, USA

Keywords:
Angiosperm woods.

Presentation Type: Colloquium Presentations
Session: CO3, Campanian-Maastrichtian floras on Laramidia: vegetation trends west of the seaway
Location: Sundance 3/Omni Hotel
Date: Wednesday, June 28th, 2017
Time: 9:00 AM
Number: CO3003
Abstract ID:345
Candidate for Awards:None