USGS scientists returned in August, 2021, to map an area of Lake Superior that has been - and continues to be - greatly impacted by a legacy of copper mining in the region. Millions of tons of waste material from the mines, locally known as “stamp sands”, were dumped into coastal waters along the Keweenaw Peninsula of Michigan during the early 20th century.
Stamp Sands Revisited: USGS Science Centers Team Up to Advance Mapping in Lake Superior
The super abundance of crushed basaltic rock caused the shoreline to accrete 100s of meters lakeward until mining largely ceased in the 1930s. Subsequent erosion has redistributed the dark-colored, metal-rich stamp sands along the shore, creating a wide beach ridge down drift of the original dump site, filling a navigation channel, and burying biologically productive areas of lake floor. With funding from the Great Lakes Restoration Initiative (GLRI), the USGS has worked with partners at the US Army Corps of Engineers and Michigan Tech University since an initial survey in 2018 (https://www.usgs.gov/center-news/mapping-stamp-sands-lake-superior) to determine the extent and volume of stamp sands near Buffalo Reef located in Grand Traverse Bay.
The 2021 survey was a joint effort between the Woods Hole Coastal and Marine Science Center (WHCMSC) and the Great Lakes Science Center (GLSC). Scientists, equipment and research vessels were mobilized from each Center during the 11-day survey between Aug 5-16. GLSC scientists Anthony Arnold, Sam Pecoraro and Chris Wright collected multibeam bathymetry and backscatter data in areas close to the beach using a Norbit iWBMSh (400 kHz) onboard the RV Desmid. WHCMSC scientists Walter Barnhardt, Brian Andrews, Alex Nichols, Eric Moore, Seth Ackerman and Patrick Berube also collected multibeam data in broader offshore areas using a dual-head Reson T20-P (400 kHz) onboard the RV Rafael. The two research teams worked simultaneously in adjacent areas of the lake, surveying along closely spaced tracklines to achieve maximum data quality in water depths as shallow as 1.5 m. For the final 3 days of the survey, the RV Rafael switched to collecting photographs, video and sediment samples of the lake floor using the SEABOSS. The combined geophysical, photographic and sampling data from both teams will support efforts to determine changes in substrate since a baseline survey in 2005 and the previous USGS survey in 2018, and to develop new methods of assessing the concentration of stamp sands in bottom sediments.
Physical conditions of the lakefloor are tightly coupled with production of fisheries for lake trout and lake whitefish that are important to the regional fishing economy and tribes. The objectives of this project are to fully characterize the spatial distribution of benthic substrates, including legacy mine wastes, to help federal/state/local/tribal partners decide on the best mitigation measures. By defining the geologic framework of the coastal system, the USGS will produce actionable information for improving the resilience of coastal environments and infrastructure to future storms and lake-level changes. The data collected on this survey will also serve to advance emerging methodologies that integrate autonomous underwater vehicles (AUVs), machine learning techniques and computer modeling to efficiently map and quantify bottom types, fish habitats and benthic organisms.