Chert from the Munsungun Lake Formation (Maine) in Palaeoamerican Archaeological Sites in Northeastern North America: Recognition of its Occurrence and Distribution

Abstract Numerous fluted point Palaeoamerican sites in the northeast contain significant numbers of chert artefacts whose origin is from the Munsungun Lake Formation in northern Maine. These sites include: Adkins, Bull Brook, Dam, Hedden, Lamareau, Michaud, Morss, Munsungun Lake (three sites), Neponset, Plenge, Point Sebago, Searsmont, Spiller Farm, Vail, Vail Kill (two sites), Wheeler Dam (two sites) and Whipple. Lithic materials in order of decreasing importance at these sites include: (1) chert whose physical characteristics are wholly consistent with chert outcrops and quarries near Munsungun Lake; (2) a variety of cherts whose physical characteristics are inconsistent with outcrops and quarries near Munsungun Lake; (3) a spherulitic, flow-banded rhyolite; (4) miscellaneous fine-grained igneous rocks; (5) clear or milky quartz; (6) miscellaneous very fine-grained or fine-grained metamorphic rocks. Portions of all collections contain artefacts which are completely weathered, and which are not assignable to any specific rock type and cannot be classified as to specific rock type. We developed a hierarchy to classify Munsungun Lake chert, ranging from hand specimen characteristics to polarized light microscopy and X-ray diffraction to chemical analysis. We conclude that hand specimen characteristics combined with polarized light microscopy are viable techniques for assigning Munsungun Lake Formation provenance. Three distinctive hand specimen features are sedimentary lamination, organic burrow structures and colour variation. Using these, chert quarries and outcrops in the geographic vicinity of Munsungun Lake may be assigned to one of the following categories: (A) structureless grayish red, dusky red, blackish red, or dark reddish brown; (B) laminated grayish red, dusky red, blackish red, or dark reddish brown chert with varve-like laminations; (C) mottled or colour laminated red and dark grey, or mottled red and greenish grey chert; (D) colour laminated and burrow mottled chert; (E) greyish to blackish laminated chert; (F) dark grey to black, structureless or weakly and thinly laminated; (G) olive grey to olive black laminated chert which is locally pyrite-rich. The nature of weathered surfaces may be a diagnostic tool for assistance in recognizing Munsungun chert. Chemical weathering tends to produce much lighter colourations and enhances the visibility of sedimentary structures. Munsungun cherts tend to weather to a very light tan, very light grey or greyish white. Radiolarians are uncommon ( Chert palaeoquarries are numerous in the Munsungun Lake area. They are of two types. One type occurs on topographically flat areas. Here the quarries are small (1×5 m) to large (5×30 m) size depressions within and along outcrops. In plan view these range in shape from roughly circular to broad ovals. Along the margins of these depressions are piles of poorly sorted worked and discarded debitage. These “tailing piles” are generally less than 1 m in height, but exhibit wide variations in areal extent and shape. Larger tailing piles overlap one another suggesting that they have experienced more than one episode of growth due to repeated quarry activity. The second quarry type occurs on steeper slopes. These are near-vertical quarried faces which range from 1 to nearly 3 m in height. Excavation here has occurred both inwards to the slope and downwards. Small cavern or adit-like “mines” have not been recognized.