41-4 Stratigraphic Distribution of Pleistocene Aves at Fossil Lake in Lake County, Oregon

Session: Paleontology, Stratigraphy, Sediments, and Soils (Posters)

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Abstract:

Fossil Lake in Lake County, Oregon, is home to a variety of Pleistocene fossil remains including vertebrates. The first fossils were found in the late 1800’s when paleontologists of the day found it to be rich in what is now known as Pleistocene fossils (Howard, 1946). Radiocarbon and ⁴⁰Ar/³⁹Ar dates show the site ranges in age from 646 ka to 11.7 ka. This puts the site in the middle to late Pleistocene (Gibbard, 2008; Martin, 2010). Most vertebrate fossils include significant numbers of fish, herpetological, mammalian, and avian remains (Martin, 2010).

The stratigraphy consists of 18 units divided into layered packages of siltstones or claystones and sandstones that cycle through time. The transgressive sandstones typically grade into silty claystones (Martin, 2017). Fossil Lake cycled through warm and wet, and cold and dry periods throughout the Irvingtonian and Rancholabrean North American Land Mammal Age (NALMA) (Martin, 2005). This work adds fossil Aves to the stratigraphic distribution of known fossil mammals, amphibians, and reptiles. From species identifications, wet versus dry cycles are determined based upon the preferred ecology of the avian species from morphological adaptation. The birds in this study are divided into three eco-types: terrestrial birds, shallow-water birds, and diving birds.

Although birds have adaptations for specific environments, their ability to fly allows them to easily travel to other locations compared to non-flying animals. Still, in this study, the aim is to see if their abundance is skewed towards their preferred habitat. Although birds migrate, they may spend a significant amount of time in their environments to feed most productively, mate, and nest. Birds are very common at Fossil Lake, and the only unit where they have not been found is Unit 18.

Some birds, like grouses, live terrestrial-based lifestyles that are largely absent of water. Identification of birds throughout the section show a cycling of terrestrial and diving birds. These groups are not commonly found within the same units. Although not all units segregate these eco-types, some skew dramatically towards specific niches of birds.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

doi: 10.1130/abs/2026SE-12667

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