2021 Field Studies, Section 1

Student exposing a fossil within one of the stratigraphic sections measured in the classic,  fossiliferous John Day and Mascall Formations we will work in

ERTH 406 Field Studies in Tectonics & Paleontology (CRN 41542) 4 credits  Instructors:  Ray Weldon and Dave Blackwell.  Graded for UO Earth Science majors; P/NP optional for all other students.  $800 course fee and usual tuition and UO fees.

This course will take students to participate in active research in the Crooked River Basin that includes rocks of classic Tertiary John Day Basin stratigraphy, interbedded with Columbia River Basalt (CRBs) and a wide variety of late Tertiary to Quaternary ash-flow tuffs, rhyolite to basalt flows, and fluvial to lacustrine deposits.  The course will include a brief introductory mapping project to familiarize students with the area, different map products, and diverse rock types and two 1-day field trips for everyone.

Fossilized mammal vertebrae in place in the John Day FormationFor 10 days students will split into stratigraphy/sedmemtology/paleotology (A) and mapping (B) groups, according to their interests. Section (A) will be taught by Dana Reuter with contributions by Samantha Hopkins and Dave Blackwell, and will focus on the fossiliferous Oligocene and Miocene deposits of the John Day and Mascall Formations and their relationship to the CRBs between them. Students will learn how to measure and describe a detailed stratigraphic section with a Jacob’s Staff and Abney Level, how to sample for paleomagnetic stratigraphy, how to survey vertebrate fossil resources and how to locate everything with GPS and a wide variety of map products. We will also learn how to collect fossils in the field, from surface collecting and screen-washing to jacketing large specimens. We’ll relate our finds to the field mapping going on at the same time, integrating paleontology with regional mapping and stratigraphy to develop a picture of the geologic history of this complex area.

The mapping group (B) will be taught by Ray Weldon with help from David Blackwell and will conduct reconnaissance-style mapping to document the distribution of the diverse units and their structural deformation.  Mapping will mainly be 1:10,000 scale on USGS geopdfs, air photos, GE imagery and LiDAR products, and will focus on characterizing two periods of rapid deformation, one largely associated with folding that accompanied arrival of the CRBs and the other that is generating faults that are active today.  Students will work in 3-person covering individually assigned, previously unmapped, areas of Tertiary to Quaternary units and structures. Group B will turn in maps, notebooks, cross sections and a brief report, and will locate and provide context for fossils that group (A) will collect.Relatively intact, lobate invasive dike with chilled margin and highly fractured, discontinuous pepperite invasive dikes of Picture Gorge Basalt injected into Mascall Formation along southeast Fossil Ridge.