Geology topics

Nigel J. Wattrus

Publications and source records attributed to Nigel J. Wattrus.

3 recordsLinked to original sources

USGS2022

Long-term hydrologic sustainability of calcareous fens along the Glacial Lake Agassiz beach ridges, northwestern Minnesota, USA

Calcareous fens are peat-accumulating wetlands fed by calcium-rich groundwater that support several threatened species of plants that thrive in these geochemical conditions. This investigation characterized the hydrology of two calcareous fens in the Glacial Lake Agassiz beach ridge complex in northwestern Minnesota, USA. Sandy surficial beach ridge aquifers and underlying buried glacial aquifers were considered as sources of groundwater to the fen. A combination of the two sources influenced by seasonal hydrology was also considered. Synchronous hydrologic responses to rainfall events and hydraulic gradients indicate the calcareous fens are well-connected to the beach-ridge aquifers. Chemistry of water discharging to the fens is calcium-magnesium-bicarbonate type similar to the beach ridge aquifers, and distinct from buried aquifers that have significant sodium and chloride. High tritium values and oxygen isotope signatures similar to the beach ridge aquifers characterized fen water. Beach ridge aquifer complexes are relatively thin (8–10 m) and overlie thick clay/clay loam till. These beach ridges exhibit high seasonal recharge and have permanent saturated zones, providing a continual source of calcium-rich water for the fens. Electrical resistivity profiles characterized the glacial stratigraphy and highlighted the well-developed physical connection between beach ridge aquifers and calcareous fens. The results of this study allow evaluation of the potential impacts of irrigation and aggregate quarrying on calcareous fens along sand and gravel beach ridges.

Minnesota↗

USGS2016

Islands in the ice stream: were spawning habitats for native salmonids in the Great Lakes created by paleo-ice streams?

Lake trout Salvelinus namaycush , lake whitefish Coregonus clupeaformis and cisco Coregonus artedi are salmonid fishes native to the Laurentian Great Lakes that spawn on rocky substrates in the fall and early winter. After comparing the locations of spawning habitat for these species in the main basin of Lake Huron with surficial substrates and the hypothesized locations of fast-flowing Late Wisconsinan paleo-ice streams, we hypothesize that much of the spawning habitat for these species in Lake Huron is the result of deposition and erosion by paleo-ice streams. This hypothesis may represent a new framework for the identification and protection of spawning habitat for these native species, some of which are currently rare or extirpated in some of the Great Lakes. We further suggest that paleo-ice streams may have been responsible for the creation of native salmonid spawning habitat elsewhere in the Great Lakes and in other glaciated landscapes.

Lake Huron↗

USGS2014

Lake trout in northern Lake Huron spawn on submerged drumlins

Recent observations of spawning lake trout Salvelinus namaycush near Drummond Island in northern Lake Huron indicate that lake trout use drumlins, landforms created in subglacial environments by the action of ice sheets, as a primary spawning habitat. From these observations, we generated a hypothesis that may in part explain locations chosen by lake trout for spawning. Most salmonines spawn in streams where they rely on streamflows to sort and clean sediments to create good spawning habitat. Flows sufficient to sort larger sediment sizes are generally lacking in lakes, but some glacial bedforms contain large pockets of sorted sediments that can provide the interstitial spaces necessary for lake trout egg incubation, particularly if these bedforms are situated such that lake currents can penetrate these sediments. We hypothesize that sediment inclusions from glacial scavenging and sediment sorting that occurred during the creation of bedforms such as drumlins, end moraines, and eskers create suitable conditions for lake trout egg incubation, particularly where these bedforms interact with lake currents to remove fine sediments. Further, these bedforms may provide high-quality lake trout spawning habitat at many locations in the Great Lakes and may be especially important along the southern edge of the range of the species. A better understanding of the role of glacially-derived bedforms in the creation of lake trout spawning habitat may help develop powerful predictors of lake trout spawning locations, provide insight into the evolution of unique spawning behaviors by lake trout, and aid in lake trout restoration in the Great Lakes.

Michigan↗