Pegrum Lecture : Late Pleistocene Ice and Outburst Floods in the Arkansas River Valley, Colorado

Given By: Nicholas Young of the SUNY Buffalo Geology Department

Mr. Young, one of the UB Geology graduate students, was kind enough to deliver a lecture on one of his side projects he's working on with Dr. Briner.

Beryllium-10 has a well constained production rate, i.e. the Be-10 totals on the surface of a rock can be used to determine how long said rock has been exposed. This dating technique is useful in that it doesn't give the age of the rock itself, but the time it has been in its present location (ideally). During the Last Glacial Maximum a glacier from the Sawatch Range, Colarado expanded to the Arkansas River Valley to impound a large lake. Flood terraces identified down-valley have been the focus of this research to determine the flood timing. Mr. Young used the Be-10 method after collecting samples of boulders on the flood terraces.

Hypothesis:
Clear creek and Pine creek glaciers crossed the Arkansas river, damming a large lake and terraces correlate to the Bull lake and Pinedale glaciations.

Conclusions:
1. Terraces formed during the Pinedale Glaciation
2. There were four Pleistocene advances
3. 17.3 Ka is not in the morraine record
4. 15.2 Ka is unique
5. Be-10 dating is reliable
- Be-10 saturation limit is ~10 Ma