by Carol Hasenberg

The geochemistry of rocks is a study that brings many great tools to the geologist’s tool chest. In the last article from October 2020, “Oxygen Isotope Analysis in Paleoclimatology,” I addressed an aspect of the geochemistry of the ocean and meteoric water on earth (meteoric water being rainwater, snow, water vapor in clouds, etc.) in the form of oxygen isotope distribution. This is a sort of shell game using stable isotopes of oxygen and how they are preferentially distributed in the waters of the earth. I will in this article explore the distribution of oxygen isotopes in rocks of the earth. These types of analyses are commonly used in many aspects of geological research and the reader will undoubtedly run across them in academic papers.

This article is not intended as a mathematical derivation of the equations used in isotope fractionation studies. (Recall that in the October 2020 article the term fractionation was described as a process of concentrating certain types of matter, in this case isotopes, in response to a phase change.) Instead, I will discuss in qualitative terms the principals that dictate how stable isotopes of oxygen distribute themselves in the rocks of the earth, and the resulting ranges of the isotopic ratios one expects to find in the rocks of the world.

by Carol Hasenberg

The intent of this article is to provide a simplified explanation for the uses of oxygen isotope analysis in determining past climatic conditions. We’ve had several speakers over the last few years who have used or made reference to this type of analysis and so you might find this information helpful in understanding a future GSOC talk.

A companion article to Andrew Dunning’s online Meetup talk about Death Valley geology to GSOC on May 16, 2020.

by Carol Hasenberg

Death Valley National Park, the largest in area in the lower 48, boasts the lowest point in North America and the world record hottest temperature. It is also the driest desert in North America, contains relief of over 11,000 feet and exposes a remarkably full geologic history spanning 2.5 billion years (2.5 Ga.). The faults that created it are part of a system that in time may become the plate boundary between the Pacific and North American tectonic plates. Significant fossil finds from many different time periods have been made in the park. The combination of all these features make it one of the most geologically valuable sites in North America.

Based on the February 14, 2020 lecture by Dr. Marli Miller, Department of Earth Sciences, University of Oregon and her book co-authored with Dr. Darrel Cowan.

GSOC members were delighted to welcome back Dr. Marli Miller to speak to the society about her latest book, Roadside Geology of Washington Second Edition. Miller co-wrote the book with her former PhD. Thesis advisor, Dr. Darrel Cowan of the University of Washington, whose experience and perspective in understanding the geological framework of the state was invaluable. In her opening remarks, she said that her favorite thing to say about writing these (roadside geology) books is that she learns so much.

In her lecture Miller broke down the geological history of Washington into a series of events, which define the physiographic provinces of the state, because it is the bedrock of a region that influences the outward appearance. The original western boundary, the Laurentian margin, is now on the eastern margin of Washington, and these ancient rocks are highly deformed and metamorphosed to varying degrees. A series of accreted terranes, starting with the Quesnellia terrane accreted in the Jurassic, and the latest Siletzia, which stretches from southern Oregon to southwestern British Columbia, and which accreted 50 million years ago, comprise the basement for the remaining part of the state. Atop and within these lie volcanic and sedimentary bodies that covered or erupted through the basement rocks. Stitching plutons were igneous masses that erupted as a result of terranes accreting to each other or to the continent.

Based on the January 10, 2020 GSOC Friday night lecture by Dr. Laird Thompson, Managing Partner of UF3.

Dr. Laird Thompson is an expert on rock fracturing and after working on imaging technology for boreholes in the 1980’s, he was appointed head of Mobil Oil’s fracture technology. He owns his own consulting firm now and is currently partnering on some work which has brought him into Oregon -- where GSOC is fortunate to have him as a speaker. He is the author or coauthor of several reference books which are the standards for the fracking* industry.

*See discussion below about whether it should be spelled “fracking” or “fracing.”

In explaining the rise and importance of fracking, Thompson reviewed the natural, financial and geopolitical history of the oil industry. Oil** is a commodity whose value is shaped by the laws of supply and demand. It is a commodity that is limited in supply. For the most part, it was created from biomass, which on earth is concentrated in the ocean in the form of diatoms, plankton, etc. These little oceanic critters have died by the trillions, and the little drops of oil they used as ballast have turned into oil reserves over millions of years.

Download pdf of Laird Thompson’s January lecture.

This article is going to be a bit of a departure from the typical GSOC Friday night lecture synopsis, because there is an online video version of the “Supervolcanoes” lecture available on Nick Zentner’s web page. However, the GSOC lecture itself was a happening due to the popularity of Zentner’s video productions, and there were some wrinkles in the Supervolcanoes lecture that he did specifically for our group that are worth noting. To begin the lecture, Zentner talked about his inspiration for doing the topic of Supervolcanoes in the Pacific Northwest.

Synopsis of the GSOC Friday night lecture given on June 8, 2019, with speaker Dr. John Armentrout

Dr. John Armentrout gave a fascinating lecture on his work on the Coaledo project, a multidisciplinary team effort to revisit the geology of Oregon’s Coos Bay area. The study area is covering the Cape Arago peninsula, from the mouth of Coos Bay to Sacchi Beach. The eighteen researchers involved in the project — specialists in geologic structure and stratigraphy, tectonics and paleomagnetics, sedimentology, and paleontology — will be updating tectonic and depositional history of the area to improve understanding at both the local and global levels of interest.