REVISITING THE "CHICKEN YARD LINE" AND THE "WHATELY FAULT", MASSACHUSETTS AND VERMONT

Originally defined by Billings (1956), the “Vermont sequence” and the New Hampshire Sequence”, have since received considerable attention as to how these two Lower Devonian sequences relate to one another, from Central Vermont to Central Massachusetts along the Connecticut River. “In one scenario the transition from the Gile Mountain formation of Vermont to the Littleton Formation of New Hampshire is an erosional unconformity marked by a quartz conglomerate in the Littleton Formation as originally defined in a chicken yard 0.5 miles south of Dutton Pines State Forest northeast of Brattleboro, Vermont (Hepburn et al., 1984). From this locale the passage from the Vermont to New Hampshire sequence is taken to occur across the “chicken yard line”, an erosional unconformity. In compiling the state geologic map of Massachusetts, Robinson et al., (1988) invoked a fault between rocks assigned by them to the Gile Mountain and Littleton Formations in the Whately Area, Massachusetts.” (Trzcienski et al., 1992). The interpretation for the Massachusetts state map and the Whately Fault was based on Robinson’s (1963) correlation of mafic volcanics and associated rocks in the Whately Area to the Erving formation that overlies the Lower Devonian Littleton Formation east of the Connecticut River . This interpretation necessitated a fault to bring older rocks over younger rocks - The Whately Fault. Adding to the confusion is a well developed, graded, east-facing channel deposit that occurs within the Gile Mountain Formation, that in the Robinson interpretation marked the “chicken yard line” in Whately, and therefore rocks to the east were Littleton Formation rocks. However, the occurrence of “punky weathering impure marble”, 10+ meters to the east of this channel deposit suggests that the channel deposit is within the Gile Mountain formation. Additionally, several hundred meters east of the exposed “Whately sequence” well cuttings from material buried under the Mesozoic sequence are consistent with the Littleton lithology and contain no carbonate material. Consequently, in the Whately area there is no Littleton Formation exposed obviating a need for a fault. A question remains, however: Does the “chicken yard line” continue into Whately or not, but under the Mesozoic cover?