14 Paleoecology of the South-Central United States (Posters)

Monday, 13 March 2023
8:00 AM - 5:00 PM
Exhibition Hall 112

PALYNOFLORA FROM THE SHORT CANYON MEMBER (ALBIAN, CRETACEOUS) OF THE CEDAR MOUNTAIN FORMATION, EMERY COUNTY, UTAH

Paper number: 14-7
Program: Theme Sessions
Time: 8:00 AM – 5:00 PM

Authors

Abstract

The Cedar Mountain Formation in east-central Utah contains a diverse, well-studied vertebrate fauna, including dinosaurs, mammaliforms, fish, amphibians, turtles and crurotarsans. Less studied are the plant fossils. Work by Tschudy, Nichols and colleagues revealed a diverse pollen (angiosperms, conifers) and spore (fern, lycopsid, moss) flora from the Cedar Mountain, with most samples from the Mussentouchit Member, the uppermost unit of the formation. Harris and Arens (2016) described an entirely angiosperm leaf flora from the upper Mussentouchit with 18 morphotypes. In this report, we describe a new palynoflora from the uppermost Short Canyon Member.

The Short Canyon Member of the Cedar Mountain Formation unconformably overlies the Ruby Ranch Member (Albian) and conformably underlies the Mussentouchit (Albian-Cenomanian). The Short Canyon Member is represented by channel deposits composed of conglomerates, fine- to coarse-grained sandstones, and carbonaceous shales. A carbonaceous sandy shale at the top of the Short Canyon above the highest conglomerate was sampled from a section adjacent to Moore Cutoff Road.

Slides contain abundant palynomorphs, cuticle and wood (tracheid and vessel fragments). The palynoflora diversity and abundance is dominated by spores (15 morphotypes, 90%) with rare conifers (4 types, 6.8%) and angiosperms (4 types, 3.2%) in a 340-grain count. The dominant genera are Deltoidospora, Gleicheniidites, and Concavissimisporites. Additional angiosperm and fern types were recorded outside the count, but Classopollis, cycad or ginkgo grains have yet to be identified. Several cuticle morphotypes, some with trichome bases, were identified. Microscopic wood fragments are difficult to identify, but the slides reveal the presence of woody angiosperms and conifers in the source flora. Preservation is bimodal with cuticle and grains easily segregated into well-preserved and poorly preserved classes. The poorly preserved class is torn, pitted, and/or colorless compared to the well-preserved class. Although reworking and transport is the probable explanation for preservation, all of the poorly preserved grains are found in the well-preserved flora (no apparent stratigraphic leakage). The paucity of windblown grains suggests local to sub-regional sourcing.

Geological Society of America Abstracts with Programs. Vol. 55, No. 1

doi: 10.1130/abs/2023SC-385130

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