BEDROCK GEOLOGY ON THE NORTHEAST FLANK OF THE PRESIDENTIAL RANGE, NEW HAMPSHIRE: A PROGRESS REPORT FOR EDMAP 2000

Bedrock geologic mapping was done in the northeastern flank of the Presidential Range of New Hampshire as part of the U.S. Geological Survey EDMAP200 program. Different members of the Devonian Littleton Formation were mapped as were the Silurian Madrid, Smalls Falls, and Rangeley Formations. Excellent exposures of original bedding, S₀, with topping directions showing equal proportions of upright and inverted bedding were found in the Littleton Formation. Two plutons of two-mica granite and one small diorite were mapped. A rare migmatitic member of the Littleton exposed along the lower elevations of Howker Ridge was also mapped. A transition from migmatized rocks to unmigmatized schists and quartzites is interpreted to be entirely within the Littleton Formation. This differs from previous interpretations which suggest that the transition is a fault separating migmatized Rangeley Formation from unmigmatized Littleton Formation. Our mapping shows no evidence for the fault and suggests that evidence for a phase of pre-metamorphic faulting is largely absent in this part of the Presidential Range. Evidence of D₁ deformation was abundant. S₁ foliation was normally found parallel to S₀, however, there were extensive areas where these fabrics were nearly perpendicular, defining two macroscopic, easterly facing F₁ folds, the Pine Link Nappe and Culhane Brook Syncline. L₁ pseudoandalusite lineations oriented parallel to F₁ hinge lines were also common. No evidence for either D₂ or D₃ deformation was seen in the study area. D₄ folding was common as both outcrop and microscale crenulations. D₅ deformation was only seen in the extreme southern end of the study area as crenulations intersecting the F₄ crenulations. Electron microprobe age dating of monazites from schists, migmatites, and granites from the study area has been done to better constrain the details of the geochronology.