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New Evidence Argues Against Younger Dryas Extraterrestrial Impact Event

Scientist in the field

The controversial Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America about 12,900 years ago resulting in massive wildfires, climate change, the extinction of many North American megafauna, and the demise of the Clovis culture. Certain "impact markers" found in the remains of old wetlands ("black mats") dated to 12,900 years ago were used as evidence for this hypothesis. If an extraterrestrial impact was the cause of such drastic change, the implications include an implied greater risk to humanity from impact events as well as these events being considered as potential triggers of rapid climate change.

GECSC geologist Jeff Pigati led a cooperative study funded by the USGS, the National Geographic Society, the Millennium Science Initiative, and Chile's National Commission on Scientific Research and Technology, to determine if the impact markers are actually inherent to the wetland systems in which the markers were originally found. The study shows that several of the markers are commonly found in black mats and other wetland deposits ranging in age from 6,000 to more than 40,000 years in areas far removed from the purported impact location. These findings suggest that the markers accumulated naturally in wetlands and are not the result of a catastrophic impact event.

Our Mission

Our world is being transformed due to climate variability, population growth, intensive land use, and the increasing demands on water, ecological, agricultural, energy, and mineral resources. To address these issues, the Geosciences and Environmental Change Science Center (GECSC) conducts research on (1) climatic, environmental, and landscape changes, (2) the geologic framework of natural resources and hazards, (3) ecological disturbance patterns resulting from natural and anthropogenic changes, and (4) the interactions among geologic, biologic, hydrologic, and human systems. This work supports policy and management decisions, the search for new sources of key materials, and the assessment of the combined environmental impacts of climate variability and human activities.

Latest Products and Highlights

February 7, 2013

Towards a publicly available, map-based regional software tool to estimate unregulated daily streamflow at ungauged rivers

By Stacey Archfield, Peter Steeves, John Guthrie (GECSC), and Kernell Ries. Published in Geoscientific Model Development, vol. 6.

This paper presents one of the first publicly available, map-based software tools to provide unregulated daily streamflow time series for any user-selected river location in a particular study region. The software tool, which requires only an internet connection, a web browser, and a macro-based spreadsheet program, was developed for the Connecticut River basin, but the overall framework is adaptable to other regions.

January 31, 2013

Challenges and opportunities for ecosystem services science and policy in arid and semiarid environments

By Ken Bagstad (GECSC), Darius Semmens (GECSC), and Charles van Riper III. Published as Chapter 4 of Colorado Plateau V: Research, environmental planning, and management for effective conservation, University of Arizona Press.

This book chapter describes the scientific challenges and policy opportunities for using ecosystem services as a management framework for the Colorado Plateau. The temporal and spatial distribution of water and the location of beneficiaries are key drivers of supply and demand for ecosystem services in this semiarid, lightly populated region. This chapter is part of a larger work synthesizing the potential contributions of recent scientific advances toward conservation and resource management on the Colorado Plateau.

January 30, 2013

The Cambrian-Ordovician rocks of Sonora, Mexico, and southern Arizona, southwestern margin of North America (Laurentia)

By Ric Page (GECSC), Anita Harris, and John Repetski. Published as Chapter 35 of The great American carbonate bank: The geology and economic resources of the Cambrian-Ordovician Sauk megasequence of Laurentia. (American Association of Petroleum Geologists Memoir 98)

This book chapter summarizes the stratigraphy, paleontology, and economic resources of Cambrian and Ordovician rocks in Sonora, Mexico and southern Arizona using selected stratigraphic reference sections. It is part of a larger publication that describes the deposits of the Great American Carbonate Bank, of North America, that comprise carbonate and clastic rocks deposited during Cambrian through earliest Middle Ordovician periods.

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