Geology topics

John W. Johnston

Publications and source records attributed to John W. Johnston.

4 recordsLinked to original sources

USGS2025

Second Integrated Hydro-Terrestrial Modeling (IHTM 2.0) workshop: USGCRP federal agency perspectives

U.S. federal leadership, mobilizing close interagency coordination across sectors, is key to tackling compound climate and human impacts on our nation’s water resources. Recognizing this need, federal agencies and academic collaborators conducted a series of workshops to advance Integrated Hydro-Terrestrial Modeling (IHTM). IHTM is focused on supporting a multiscale framework to accelerate research insights, better integrate operational and planning perspectives, and bridge national-to-regional capabilities to address major interdependent societal water challenges. This framework leverages the capabilities of different agencies and institutional partners across sectors to advance a shared vision for use-inspired modeling and open science. The IHTM conceptual framework has developed over several community workshops in recent years: ● In September 2019, a community coordinating group on IHTM hosted an interagency workshop (“IHTM 1.0”) with support from NSF, DOE, and USGS. The resulting report identified the need for agencies to invest resources in designing pilot use cases, setting the stage for an integrated national IHTM capability. ● In November 2020, the U.S. Global Change Research Program (USGCRP) held a virtual Coastal-IHTM (C-IHTM) workshop in collaboration with the MultiSector Dynamics Community of Practice, which engages researchers across universities and national labs. Building on IHTM 1.0, this workshop aimed to identify coastal modeling capabilities and appropriate coastal applications of the IHTM framework. The workshop report detailed needs for open science, geographical or topical use cases, integrated modeling frameworks, and linking communities of practice. ● From October 31 to November 2, 2023, USGCRP hosted a hybrid IHTM 2.0 community workshop that brought together 160 scientists and managers from nine federal departments/agencies (DHS-FEMA, DOC-NOAA, DoD-USACE, DOE, DOI [U.S. Bureau of Reclamation (USBR), USGS], EPA, NASA, NSF, USDA [ARS, FS, NRCS]) and 32 non-federal academic, non-profit, and private institutions and consortiums. The workshop was organized by a federal Interagency Steering Committee with representatives from DOE, USGS, NSF, NASA, and NOAA, as well as a Scientific Organizing Committee comprising experts from academia and additional federal agency technical experts. The IHTM 2.0 workshop focused on moving the IHTM 1.0 concepts to action by making advances in designing national and regional integrated modeling experiments in five geographic testbeds. These modeling testbeds seek to facilitate collaborative water resources research and assessment that responds to societal needs, extending from basic research to resource management operations, including the assessment of water quantity, quality, and use at national and regional scales. Ultimately, we envision that the IHTM testbeds will improve our ability to provide water resources assessment scenarios to decision-makers and the public. This document summarizes USGCRP and member agencies’ perspectives of the IHTM 2.0 workshop. Sections 2 and 3 build on the work of the IHTM 2.0 workshop Scientific Organizing Committee to outline the importance of IHTM, summarize the workshop, and propose near- and medium-term IHTM priorities. Section 4 presents select ongoing and potential interagency activities that could help realize the IHTM 2.0 vision and align with three of USGCRP’s strategic goals for this decade: Advancing Science, Informing Decisions, and Engaging the Nation. Finally, Section 5 summarizes this report and offers information about how to connect with USGCRP’s IHTM activities. USGCRP and its member agencies are well-positioned to coordinate federal efforts to enhance IHTM capabilities in the coming years.

Conference Paper↗

USGS2017

Optically stimulated luminescence dating of late Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan, USA

This study evaluates the accuracy of optically stimulated luminescence to date well-preserved strandline sequences at Manistique/Thompson bay (Lake Michigan), and Tahquamenon and Grand Traverse Bays (Lake Superior) that span the past ∼4500 yr. The single aliquot regeneration (SAR) method is applied to produce absolute ages for littoral and eolian sediments. SAR ages are compared against AMS and conventional 14 C ages on swale organics. Modern littoral and eolian sediments yield SAR ages <100 yr indicating near, if not complete, solar resetting of luminescence prior to deposition. Beach ridges that yield SAR ages <2000 yr show general agreement with corresponding 14 C ages on swale organics. Significant variability in 14 C ages >2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 ± 390 yr (UIC913) on ridge77 at Tahquamenon Bay is consistent with regional regression from the high lake level of the Nipissing II phase ca. 4500 cal yr B.P. SAR ages indicate a decrease in ridge formation rate after ∼1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to 14 C methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where 14 C methods prove problematic.

Quaternary Research↗

USGS2004

Late Holocene lake-level variation in southeastern Lake Superior: Tahquamenon Bay, Michigan

Internal architecture and ages of 71 beach ridges in the Tahquamenon Bay embayment along the southeastern shore of Lake Superior on the Upper Peninsula of Michigan were studied to generate a late Holocene relative lake-level curve. Establishing a long-term framework is important to examine the context of historic events and help predict potential future changes critical for effective water resource management. Ridges in the embayment formed between about 4,200 and 2,100 calendar years before 1950 (cal. yrs. B.P.) and were created and preserved every 28 ± 4.8 years on average. Groups of three to six beach ridges coupled with inflections in the lake-level curve indicate a history of lake levels fluctuations and outlet changes. A rapid lake-level drop (approximately 4 m) from about 4,100 to 3,800 cal. yrs. B.P. was associated with a fall from the Nipissing II high-water-level phase. A change from a gradual fall to a slight rise was associated with an outlet change from Port Huron, Michigan/Sarnia, Ontario to Sault Ste. Marie, Michigan/Ontario. A complete outlet change occurred after the Algoma high-water-level phase (ca. 2,400 cal. yrs. B.P.). Preliminary rates of vertical ground movement calculated from the strandplain are much greater than rates calculated from historical and geologic data. High rates of vertical ground movement could have caused tectonism in the Whitefish Bay area, modifying the strandplain during the past 2,400 years. A tectonic event at or near the Sault outlet also may have been a factor in the outlet change from Port Huron/Sarnia to Sault Ste. Marie.

Michigan↗

USGS2004

Reconstructing paleo lake levels from relict shorelines along the Upper Great Lakes

Shorelines of the upper Great Lakes include many embayments that contain strandplains of beach ridges. These former shoreline positions of the lakes can be used to determine changes in the elevation of the lakes through time, and they also provide information on the warping of the ground surface that is occurring in the Great Lakes after the weight of glacial ice was removed. Relative lake-level hydrographs can be created by coring the beach ridges to determine the elevation of basal foreshore (swash zone) deposits in each ridge and by obtaining radiocarbon dates of basal wetland sediments between ridges to generate an age model for the ridges. Because the relative-level hydrographs are the combination of lake-level change and vertical ground movement (isostatic rebound), the rebound must be removed to produce a graph that shows only the physical limits and timing of past lake-level fluctuations referenced to a common outlet. More than 500 vibracores of beach-ridge sediments were collected at five sites along Lake Michigan and four sites along Lake Superior. The cores showed a sequence of dune deposits overlying foreshore deposits that, in turn, overlie upper shoreface deposits. The base of the foreshore deposits is coarser and more poorly sorted than an overlying and underlying sediment and represents the plunge-point sediments at the base of the swash zone. The plunge-point deposits are a close approximation of the elevation of the lake when the beach ridge formed. More than 150 radiocarbon ages of basal wetland sediments were collected to produce age models for the sites. Currently, age models exist for all Lake Michigan sites and one Lake Superior site. By combining the elevation data with the age models, six relative lake-level hydrographs were created for the upper Great Lakes. An iterative approach was used to remove rebound from the five Lake Michigan relative hydrographs and merge the graphs into a single hydrograph. The resultant hydrograph shows long-term patterns of lake-level change for lakes Michigan and Huron and is referenced to the Port Huron outlet. When the age models are completed for the Lake Superior sites, a hydrograph will be created for the entire lake.

Aquatic Ecosystem Health & Management↗