Mapping projects

Coal seams interlayered with white sandstone of the Miocene Suntrana Formation, near Healy.

Healy – northern foothills of the Alaska Range

The first project outside of Fairbanks takes us south to the foothills of the Alaska Range near the town of Healy. We will encounter metamorphic and young, barely lithified, sedimentary rocks, mainly conglomerate, sandstone and coal. The coherent stratigraphy and modest structural complications makes this area ideal for recognizing contacts between units, and relating 3D geology to a 2D map. We will practice drawing and interpolating geologic contacts, creating geologic cross-sections and identifying structures based on exposed and inferred geology.

Instructors in Healy: Prof. Rainer Newberry, Dr. Jochen Mezger and a TA

Measuring the layering of felsic volcanic rocks in Denali National Park & Preserve.

Denali National Park & Preserve – Alaska Range

After a short break in Fairbanks the Field Camp will relocate for ten days to Denali National Park & Preserve. This project is ‘intermediate’ in length, amount of assistance, difficulty, mapping style, scale and access between the Healy and Limestone Gap projects. The camp will be set up in a gravel pit with two office tents and the cook truck serving as the mobile kitchen. We intend on mapping every day, at a scale of 1:20,000, in groups of 3-5 students along with a ‘geobuddy’. Each student will individually prepare a map, a cross-section, and a report.

The rocks we will encounter are Cretaceous sedimentary rocks, Tertiary volcanic rocks and volcanic conglomerates, as well as cross-cutting felsic plutons and mafic dikes. Regional faulting and folding result in more complex structures.

Instructors in Denali: Prof. Paul McCarthy, Dr. Jochen Mezger, Prof. Sean Regan and a TA

Walking over the Nelchina Limestone towards Billy Mountain at Limestone Gap.

Limestone Gap – Talkeetna Mountains

Following several days in Fairbanks to finish the Denali report, the Field Camp heads out southeast to the eastern Talkeetna Mountains. Flying out of Sheep Mountain along the Glenn Highway with a small bush plane, the campsite of Limestone Gap is located on a meadow at 5000 feet elevation. For the next three weeks our little camp, a cook tent and two office tents surrounded by a ring of private tents, will call this magnificent tundra landscape home.

The circumstances for mapping are ideal: no need to worry about breaking trail through bush, the geology is well-exposed. The section consists of a Late Jurassic to Cretaceous mostly marine sequence, including black shales of basin origin, storm deposits, and lagoonal or non-marine calcareous clastic rocks. The section is unconformably overlain by a thick section of Tertiary basalts. Basaltic dikes related to the extrusive rocks intrude the clastic section. The sedimentary rocks are highly fossiliferous; ammonites, belemnites, and bivalves are common in parts of the section. The area is located near the eastern limits of the Castle Mountain – Caribou fault system of south-central Alaska, and the layered rocks are faulted and folded in patterns that are a challenge for students to map and explain.

Work in the area begins with measuring and describing several stratigraphic sections, defining map units, and interpreting the depositional history. The remainder of work at Limestone Gap is devoted to completing a geologic map of the 5 km x 6 km study area at a scale of 1:10,000. The structure of the area is diverse and complex, but well-defined marker units, good exposures, and easily negotiated terrain allow students to focus their efforts on locating and tracing contacts on their maps. Students must map contacts of folded and faulted units, faults, and fold axial surfaces, identify different types of faults, and evaluate whether their maps make geologic sense. The conclusion of the project involves compilation of a complete map, preparation of cross sections, interpretation of geologic history based on the mapped cross-cutting relations, and preparation of a report.

Instructors in Limestone Gap: Dr. Jochen Mezger, Prof. Mike Whalen, Prof. Sarah Fowell, Prof. Elisabeth Nadin and a TA

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