STRATIGRAPHY, DEPOSITIONAL ENVIRONMENTS AND STRUCTURE OF SILURIAN FLYSCH DEPOSITS IN THE GREATER BANGOR AREA, CENTRAL MAINE

The stratigraphic section in the greater Bangor area is comprised of two formational units that are part of the Vassalboro Group. These units then are approximate correlatives to the Waterville and Mayflower Hill formations to the southwest. The formations are informally referred to as the Brewer and Bangor formations in ascending stratigraphic order. The Bangor Formation has three recognizable members. In ascending order these are the Penobscot River Member, the Lover’s Leap Member and the Kenduskeag Stream Member. The Brewer Formation is primarily a siltstone and claystone slate with locally present thin sandstone beds are generally thin. The Penobscot River Member is metasandstone and is divided into two facies, a lower thick bedded facies and an upper thin bedded facies. These rocks exhibit structures consistent with deposition from submarine fan turbidites which uncommonly exhibit sole markings and ripple structures consistent with a source to the modern day southeast. The Lover’s Leap Member is identical in composition to the Brewer Formation. Sandstones of the Kenduskeag Stream Member are more feldspathic. Paleontologically, the Lover’s Leap yielded microfossils confined to the Wenlock while the Brewer Formation yielded an earlier Silurian age (Ludman et al. 2020 Am. Jour. Sci p. 296). The Flume Ridge Formation is recently recognized and separated from the Brewer Formation. Initial mapping in 2004 placed 10 outcrops within the Brewer Formation. Reappraisal of these outcrops in 2021 indicate that these metasandstones are consistent with Flume Ridge Formation. Sparse outcrops suggest that the Flume Ridge conformably underlies the Brewer Formation. The southerly portion of the Flume Ridge terminates against a splay from the Liberty Orrington thrust fault. The lower contact of the Flume Ridge is a well – defined pseudotachylyte bearing fault here interpreted as a continuation of the Hackmatack Pond Fault which is recognized to separate the Vassalboro Group from the Falmouth Brunswick sequence to the south. In this area the Flume Ridge is in contact with the Cape Elizabeth Formation along the fault. Further southeast the Cape Elizabeth Formation is faulted against the Bucksport Formation. This fault is interpreted to be a continuation of the Ray Corner Mylonite Zone.