Geology topics

Jeremy C. Havens

Publications and source records attributed to Jeremy C. Havens.

7 recordsLinked to original sources

USGS2026

Reconstructing the Quaternary depositional history using geologic mapping and three-dimensional modeling of the subsurface near Fort Morgan, northeastern Colorado

Centered on Fort Morgan, Colorado, this study is intended to build from previous work by adding a three-dimensional (3D) view of the subsurface to better understand the depositional history of Quaternary deposits. A 1:100,000 scale geologic map was made by combining previous geologic maps, regional soil maps, and recent field investigations. In addition to the geologic mapping, drill hole lithologic data from water wells and oil and gas exploration were compiled and lithologic units simplified to best represent the stratigraphy of the Quaternary deposits. From these subsurface data, a 3D subsurface model was constructed, trimmed at the surface by a digital elevation model, and a bedrock surface foundation gridded from drill hole data was added. The surface of the 3D model was then compared visually to the surficial geologic map. Cross sections were constructed from the 3D model and compared to site-specific drilling that was done as part of this project. Finally, the model was examined in detail to reconstruct the depositional history of the subsurface alluvial and eolian units. Alluvial and fluvial drainage basins exposed in the subsurface have a greater areal extent than the present-day narrow drainages. Older eolian sand in the subsurface tends to be interbedded with loess indicating coeval deposition. Holocene sand, both eroded from bedrock exposed at the surface north of the study area and reworked from the South Platte River, buries most of the interbedded older sand and loess.

Colorado↗

USGS2025

U.S. Geological Survey 2024 Rocky Mountain Region Science Exchange—Showcasing cutting-edge science to adapt to extreme weather events and stakeholder needs

Introduction The Rocky Mountains and the Colorado River Basin in the Western United States are complex, interconnected systems that sustain a large variety of species, including tens of millions of humans. These regions face risks from drought, wildfires, invasive plant and animal species, and habitat reduction. Working with many stakeholders, scientists can help to characterize these risks by providing data and analytical tools to inform land and water resource management decisions. The U.S. Geological Survey 2024 Rocky Mountain Region (Region 7) Science Exchange Workshop, held in April 2024, focused on cutting-edge science techniques, evaluating complex interconnected risks, and coproducing science with science partners and stakeholders. These science topics and communication strategies can be used for developing data, interpretations, and decision support tools needed to provide science that resource managers and other stakeholders can use to better understand complex, dynamic natural systems and develop management strategies to plan for and adapt to risks that threaten human communities and natural ecosystems.

Fact Sheet↗

USGS2023

Geologic map and hydrogeologic investigations of the upper Santa Cruz River basin, southern Arizona

This report includes an updated geologic map and cross sections of the upper Santa Cruz River basin, southern Arizona. The map and cross sections describe the geometry, thickness, and structure of the Miocene to Holocene units which form the main aquifers in the basin. The report also includes results of new hydrogeologic studies including (1) mapping and defining depth to bedrock based on geophysical data in the map area to better define the geometry and structure of the basin aquifers, (2) describing newly recognized hydrologically significant faults in the Peck Canyon and Sopori Wash areas, and (3) evaluating groundwater sources and hydrogeology of the Potrero Creek wetlands.

Arizona↗

USGS2022

Holocene paleohydrology from alpine lake sediment, Emerald Lake, Wasatch Plateau of central Utah, USA

Holocene sediments at Emerald Lake in central Utah (3090 m asl) document the paleohydroclimatic history of the western Upper Colorado River headwater region. Multi-proxy analyses of sediment composition, mineralogy, and stable isotopes of carbonate (δ 18 O and δ 13 C) show changes in effective moisture for the past ca. 10,000 years at millennial to decadal timescales. Emerald Lake originated as a shallow, closed-basin cirque pond during the Early Holocene. By ca. 7000 cal yr BP, higher lake levels and carbonate δ 18 O values indicate rising effective moisture and higher proportions of summer precipitation continued at least until ca. 5500 cal yr BP when a landslide entered the lake margin. Between ca. 4500 and 2400 cal yr BP dry conditions at Emerald Lake envelop the timing of the ‘Late Holocene Dry Period’ identified at lower elevations. For the past ca. 2500 years, Emerald Lake δ 18 O values were relatively low, indicating wetter conditions and higher snow input (compared to rain), except for dry periods at ca. 2000 cal yr BP and during the Medieval Climate Anomaly at ca. 1000 and ca. 500 cal yr BP. Results provide a long-term perspective on precipitation extremes that influence regional water supplies from a snow-dominated catchment typical of the predominant source region for the Upper Colorado River.

Utah↗

USGS2020

Boreal blazes: Biomass burning and vegetation types archived in the Juneau Icefield

The past decade includes some of the most extensive boreal forest fires in the historical record. Warming temperatures, changing precipitation patterns, the desiccation of thick organic soil layers, and increased ignition from lightning all contribute to a combustive combination. Smoke aerosols travel thousands of kilometers, before blanketing the surfaces on which they fall, such as the Juneau Icefield. However, many aerosols found in smoke plumes are also produced by other processes and therefore can be ambiguous indicators of fire activity. Here, we use the monosaccharide anhydrides levoglucosan, mannosan, and galactosan as specific indicators of biomass burning to unambiguously demonstrate that fire aerosols reach the Juneau Icefield and are integrated into the snowpack. Back trajectories and satellite observations demonstrate that smoke plumes originating in central Alaska and eastern Siberia affect the Juneau Icefield. These regional sources of fire differ from other combustion aerosols deposited on the Juneau Icefield, such as black carbon, that originate from local fossil fuel burning. Ratios of levoglucosan/mannosan (L/M) and levoglucosan/(mannosan + galactosan) (L/(M + G)) demonstrate that while the majority of fire aerosols reaching the Juneau Icefield originate from softwood burning, grasslands and hardwood forests are also sources. The presence of these hardwoods suggests that fire aerosols may reach the Juneau Icefield from locations as far away as East Asia.

Alaska↗

USGS2017

Investigating the landscape of Arroyo Seco—Decoding the past—A teaching guide to climate-controlled landscape evolution in a tectonically active region

Introduction Arroyo Seco is a river that flows eastward out of the Santa Lucia Range in Monterey County, California. The Santa Lucia Range is considered part of the central California Coast Range. Arroyo Seco flows out of the Santa Lucia Range into the Salinas River valley, near the town of Greenfield, where it joins the Salinas River. The Salinas River flows north into Monterey Bay about 40 miles from where it merges with Arroyo Seco. In the mountain range, Arroyo Seco has cut or eroded a broad and deep valley. This valley preserves a geologic story in the landscape that is influenced by both fault-controlled mountain building (tectonics) and sea level fluctuations (regional climate). Broad flat surfaces called river terraces, once eroded by Arroyo Seco, can be observed along the modern drainage. In the valley, terraces are also preserved like climbing stairs up to 1,800 feet above Arroyo Seco today. These terraces mark where Arroyo Seco once flowed.The terraces were formed by the river because no matter how high they are, the terraces are covered by gravel deposits exactly like those that can be observed in the river today. The Santa Lucia Range, Arroyo Seco, and the Salinas River valley must have looked very different when the highest and oldest terraces were forming. The Santa Lucia Range may have been lower, the Arroyo Seco may have been steeper and wider, and the Salinas River valley may have been much smaller. Arroyo Seco, like all rivers, is always changing. Some-times rivers flow very straight, and sometimes they are curvy. Sometimes rivers are cutting down or eroding the landscape, and sometimes they are not eroding but depositing material. Sometimes rivers are neither eroding nor transporting material. The influences that change the behavior of Arroyo Seco are mountain uplift caused by fault moment and sea level changes driven by regional climate change. When a stream is affected by one or both of these influences, the stream accommodates the change by eroding, depositing, and (or) changing its shape. In the vicinity of Arroyo Seco, the geologically young faulting history is relatively well understood. Geologists have some sense of the most recent faulting event and of the faulting in the recent geologic past. The timing of regional climate changes is also well accepted. In this area, warm climate cycles tend to cause the sea level to rise, and cool climate cycles tend to cause the sea level to fall. If we understand the way the terraces form and their ages in Arroyo Seco, we can draw conclusions about whether faulting and (or) climate contributed to their formation. This publication serves as a descriptive companion to the formal geologic map of Arroyo Seco (Taylor and Sweetkind, 2014) and is intended for use by nonscientists and students. Included is a discussion of the processes that controlled the evolution of the drainage and the formation of the terraces in Arroyo Seco. The reader is guided to well-exposed landscape features in an easily accessible environment that will help nonscientists gain an understanding of how features on a geologic map are interpreted in terms of earth processes.

California↗

USGS2017

Constraints on the age of the Great Sand Dunes, Colorado, from subsurface stratigraphy and OSL dates

The age of the Great Sand Dunes has been debated for nearly 150 yr. Seven ages ranging from Miocene to late Holocene have been proposed for them. This paper presents new information—chiefly subsurface stratigraphic data, OSL dates, and geomorphic evidence—that indicates that the Great Sand Dunes began to form in the latter part of the middle Pleistocene. The dunes overlie a thick wedge of piedmont-slope deposits, which in turn overlies sediment of Lake Alamosa, a paleolake that began to drain about 440 ka. The wedge of piedmont-slope deposits extends westward for at least 23 km and is as much as 60 m thick at a distance of 10 km from the Sangre de Cristo Range. Ostracodes from one well indicate that the eastern shoreline of Lake Alamosa extended to within 4.3 km of where the Great Sand Dunes eventually formed. The time represented by the wedge of piedmont-slope deposits is not known exactly, but the wedge post-dates 440 ka and was in place prior to 130 ka because by then the dunes overlying it were sufficiently close and tall enough to obstruct streams draining from the Sangre de Cristo Range.

Quaternary Research↗