Evolution of carbonate studies in the Rocky Mountain region over the past century

Abstract

Just as the world’s population, knowledge in general, and the Rocky Mountain Association of Geologists (RMAG) have changed in major ways during the past 100 years, so too has the study and interpretation of carbonate rocks and reservoirs. The RMAG, a century old in 2022, has evolved from just 50 original charter members who held the organization’s first “meeting” in 1922, to its approximately 1800 members today. Thus, RMAG’s publications have helped document the evolution of carbonate rock studies, particularly those in the Rocky Mountain region. Key contributions have been made through RMAG’s hundreds of luncheon talks, through its quarterly technical publication, The Mountain Geologist, initiated in 1964, and the exceptionally comprehensive Geologic Atlas of the Rocky Mountain Region, published 50 years ago in 1972. In addition, since 1953 the RMAG has published field guides and symposia volumes focused on specific basins, types of reservoirs, and structural geology among other things. Many of these books contain papers focused on carbonate rock units in the Rockies. Analysis of the papers published in The Mountain Geologist each year from 1964 through 2021 reveals that a fairly consistent 10 to 15% of that journal’s articles each year deal directly with some aspect of carbonate rocks. Earlier papers in the 1960s and 1970s dealt mainly with outcrop studies and the correlation of specific carbonate units based on measured sections or the use of fossils to define facies and biostratigraphic units. During the 1980s emphasis shifted to refining carbonate depositional models and focusing more on carbonate diagenesis through detailed petrographic studies, isotopic analyses, cathodoluminescence, and scanning electron microscopy. The 1990s brought a shift to papers focused more on specific carbonate hydrocarbon reservoirs ranging from the peritidal dolomites in Cottonwood Creek Field to relatively deepwater Waulsortian mudmounds in the Mississippian Lodgepole Formation and the “basinal” chalks of the Niobrara Formation. The focus of carbonate studies shifted again in the early 2000s to the use of 3-D seismic data to better understand specific carbonate reservoirs and the increased interpretation of carbonate deposits within the context of sequence stratigraphy. The tools used to study carbonate rocks expanded even further over the past decade with more refined isotopic data, improved SEM studies, and the use of elemental data obtained with X-ray fluorescence analyses. No doubt the next decade will bring even more improvements in data collection methods and the interpretation of depositional and diagenetic processes that have impacted all Rocky Mountain carbonate deposits.