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Abstract Detail



The Miocene vegetation and environment of Western North America

Dillhoff, Thomas [1].

Fossil Wood from the Middle Miocene of Washington State: A New Species of Engelhardioxylon (Juglandaceae: Engelhardieae).

Fossil wood associated with the Columbia River Flood Basalts has been known for nearly a century. The best known and most extensively studied wood locality in the region is the large deposit of silicified wood near the town of Vantage in central Washington State. While the Vantage site has garnered most of the attention, there are a number of other Miocene wood localities in the region that have been extensively collected by amateurs and scientists since the first half of the twentieth century. These localities share many of the taxa that are found at Vantage, but also include several types that have not yet been described in the scientific literature. Further study of the wood from these deposits has the potential to increase the known diversity of woods from the region and expand our knowledge of the middle Miocene floras of the Pacific Northwest. One significant find is the recent identification of a new species of Engelhardioxylon collected during the 1960s from a now defunct gravel quarry in the Saddle Mountains of central Washington. This wood type is rare in the fossil record with only four previously described species worldwide, ranging from the middle Eocene of North America, the late Eocene of Germany, and the Oligocene of eastern Russia. The mid-Miocene Saddle Mountain species is thus the youngest known occurrence of fossil Engelhardioxylon wood. The new type possesses both simple and scalariform perforation plates, which is the main feature that distinguishes the Engelhardieae from other tribes within the Juglandaceae. Vessel arrangement is semi-ring porous with vessels solitary and in radial multiples of 2-4(6). Thin walled tyloses are common, intervascular pits are alternate. Axial parenchyma are in apotracheal tangential bands 1-2 cells wide; parenchyma bands are more frequent in latewood. Rays are homocellular to weakly heterocellular, 1- to 2- seriate, mostly uniseriate. The presence of the Engelhardieae in the Miocene Pacific Northwest is supported by previous records of rare fossil Engelhardioid fruits from lacustrine deposits along the eastern margin of the Columbia River Flood Basalts, and has the potential to help constrain paleoclimate estimates given the thermophilic nature of all extant genera within the tribe.


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1 - Evolving Earth Foundation, PO Box 2090, Issaquah, WA, 98027, USA

Keywords:
Miocene
Juglandaceae
Engelhardieae
Washington State
Wood anatomy.

Presentation Type: Symposium or Colloquium Presentation
Session: C2
Location: Salmon/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 3:45 PM
Number: C2010
Abstract ID:259
Candidate for Awards:None


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