Curved Mountain Range Origins Through Paleomagnetism

Posted May 10th, 2010 at 9:53 am.

Evan Pugh & Matt Tomich

Mentor: Dr. Arlo Weil

Paleomagnetism is the study of the Earth’s ancient magnetic field as it is recorded in the rock record. Using paleomagnetism to measure the magnetic elements in rocks helps geologist determine the way rock formations were aligned and positioned in the distant past. With this information one can extrapolate where, and in what orientation the rocks were in relation to the Earth’s spin axis. This data can then be juxtaposed with the rock formation’s current location and position to quantify the amount of motion or rotation an area has undergone since its formation. Working with Professor Arlo Weil in the Wyoming Salient, which extends from Salt Lake City, Utah north to Jackson Hole, Wyoming, Evan Pugh and Matt Tomich helped gather data that will potentially show how a curved mountain range has become curved and what it originally looked like. Rock cores were drilled in the field and brought back to Bryn Mawr’s paleomagnetism lab to be examined.

The Wyoming Salient was chosen because of its overall curved appearance in map view. Mountain ranges do not usually form in bowed shapes unless they are along the coast of ancient continents. Dr. Weil has also studied curved mountain belts in Portugal, North Africa and Spain. The data Dr. Weil has gathered over a series of consecutive summers from over two hundred sites in the Wyoming Salient should create a bounded area of time in which the regions tectonic history can be unraveled.

This summer in the field nearly seventy new sites were visited. At each site cores were drilled and structural measurements were made. Using a diamond-bit drill, cores with one inch diameter were bored out of the surrounding formation. At every site detailed structural data (including measurements of bedding, faults, folds, cleavage, etc.) were taken with a Brunton geologic transit and recorded to allow restoration of the cores back in the lab back at Bryn Mawr. In addition to the structural measurements, basic paleomagnetic data was taken in the field for each core removed. All of this information will allow Dr. Weil and his colleagues to reconstruct the conditions of the field back in the laboratory.

Hopefully this summer’s set of rock cores, which is in the process of being examined in the laboratory, will augment Dr. Weil’s previous findings in the area and lead to a general understanding of how the curvature of this portion of the Rocky Mountains was acquired. Perhaps these results will ultimately shed light on some of the mysteries of other curved mountain ranges throughout the rest of the world.

Filed under: 2005,Pugh, Evan,Tomich, Matt,Weil, Dr. Arlo by Ann Dixon

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