Abstract The Late Quaternary geomorphology and stratigraphy of the Big Fork River valley, within the Rainy River basin of northern Minnesota, reveals evidence of prehistoric human interaction with late Holocene riverine environments. By 11 000 14 C BP, deglaciation made the region inhabitable by human groups using Clovis artefacts. Human habitation would also have been possible during the Moorhead low-water stage of glacial Lake Agassiz, starting at 10 500 14 C BP. Near its confluence with the Rainy River, the valley floor of the Big Fork valley consists of a floodplain complex and two terraces. The multi-component stratified Hannaford site is situated within the active floodplain. Overbank deposits contain artefacts in primary context, whereas artefacts within the point bar deposits are in secondary archaeological context; these deposits are associated with changing alluvial settings as the river moved eastward. Aggradation of the valley fill beneath the lowest surface (T 0 , floodplain complex) began by 3000 years ago and is associated with human activities focused on seasonal fishing and the use of riparian resources from 1300 to 650 14 C BP.

Abstract Big Eric’s Crossing (Fig. 1, Site 1) is a county bridge acrossthe Huron River (NW¼NW¼Sec.35, T.52N., R.30W.), Skanee, Michigan 15-minute Quadrangle, about 12 mi (19 km) northeastof L/Anse, Michigan, along the road that continues north fromMain Street. The second locality (Site 2), a small, southeastfacinggranite hill, (SE¼:SE¼Sec.26) is about 1 mi (1.6 km)nrtheast of the bridge and lies about 600 ft (200 m) south of the road. Big Eric/s Crossing is a famous fishing spot on the HuronRiver, and Baraga County maintains a campground at the bridge.The river is high from late September until late May, so theoutcrops along the river are best visited during the middle andlate summer. Sites 2 and 3 are on private land. However, so long as visitsare brief, and visitors continue to respect the surface and theexposures, property owners in the Upper Peninsula tend not topost their lands.

Cenomanian to Turonian marine strata exposed in the Big Sioux River Valley of Iowa and South Dakota contain numerous concretion horizons. Concretion-bearing strata from the upper Dakota (type), Graneros, Greenhorn, and Carlile Formations were studied near their erosional limits along the eastern margin of the Western Interior Seaway. Concretion horizons formed in beds with concentrations of fossiliferous debris, including fish-scale siltstones with starved megaripple bedforms, inoceramid and inoceramid-ostreid packstones, and dense bioturbated accumulations of ammonoids and inoceramid, ostreid, and other bivalves. Concretions in the Carlile contain paleontologic and sedimentologic indicators for a general upward shallowing sequence, with nonmarine environments represented within the Codell Sandstone Member. Petrographic and stable isotopic data on diagenetic carbonates in the Carlile provide evidence for the early establishment of meteoric phreatic environments (δ 18 O = −7 ‰), although modified marine phreatic environments (δ 18 O = −2.5 ‰) are also represented. Variable degrees of fluid-rock interaction resulted in highly variable carbon isotopic compositions of diagenetic carbonates from both environments. Skeletal calcites from inoceramid and ostreid bivalves that inhabited dysaerobic benthic environments have anomalously low δ 18 O values and do not provide an accurate record of ambient seawater chemistry because of vital effects, possibly related to the activity of chemosynthetic symbiotic bacteria. Data from diagenetic carbonates in the Carlile are consistent with a proposed long-term secular trend of increasing oxygen isotopic ratios in Turonian (−2.5 ‰) to Maastrichtian (−0.5 ‰) marine carbonates from the Western Interior Seaway, probably related to global cooling. Petrographic and geochemical evidence for deep infiltration of dilute meteoric fluids during late Turonian subaerial exposure of Carlile strata, and relatively small marine phreatic–meteoric phreatic δ 18 O shifts in carbonate cements, are suggestive of humid paleoclimates along the eastern margin of the seaway, and conflict with prior suggestions of semiarid to slightly evaporitic paleoclimates in the area.