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Directions: Park at the picnic site and walk to the falls (FIG). This site is a great place for swimming but watch out for rocks.
The Smalls Falls Formation lies on top of the Perry Mountain Formation and comprises mainly black, rusty shale (FIG). The black color is due to graphite (carbon) and the rust to iron sulfide minerals. Carbon and iron sulfide indicate a reducing environment in sharp contrast to the light-colored "oxygenated" sediments below. The cause of this sudden change to a reducing environment is unknown; it may be unrelated to local events.
The shales have been metamorphosed. Look for "Maltese crosses" of chiastolite (FIG), a variety of andalusite. Above the falls, a tight fold may be observed.
The Smalls Falls Formation completes the fining upwards sequence; mountains in the Taconica source area had been levelled (STAGE III-B).
Directions: Park on the wide shoulder along the hairpin turn above the Smalls Falls picnic area. Watch for traffic and cross to the long roadcut on the inside of the curve.
The Perry Mountain Formation consists mainly of sandstones rich in quartz. Look for graded beds (FIG) having sharp sandy bases grading up into shale. In which direction does the sequence become younger? The graded beds suggest deposition by "turbidity currents", slurries of sediment moving downslope due to gravity, in deep water. Also note the metamorphic minerals biotite and staurolite. The Perry Mountain Formation signifies waning erosion of the Taconica are terrane that was previously rugged and subsequently levelled (STAGE III-B).
Directions: This site consists of a long roadcut on the east side of Route 4 about 4 miles south of Rangeley. Park on the shoulder.
Note the rounded boulders (FIG), which are believed to have been transported from the northwest. Do any of them resemble the Attean Granite (Stop 14)?
Sediments making up the Rangeley Formation record the unroofing of the uplifted arc region (Taconica, stops 13-21) to the northwest following its collision with Laurentia (STAGE III-B).
Directions: From Madrid, continue south crossing two bridges. After the southern bridge and while driving uphill, a large outcrop will be seen on the inside of a curve to the left (east).
The Carrabasset Formation comprises a thick sequence of graded beds of sandstone and dark shale. Determine the top direction. The shales are strewn with metamorphic staurolite crystals (FIG). Some of the crystals occur in pairs forming crosses. Mud-rich sediments of the Carrabassett and Seboomook Formations flooded central and northern Maine during early Devonian time (Stage IV-A). They are the precursor of the collision of Avalonia with Laurentia. They are believed to have an eastern source and to have been deposited in a deep water trench environment.
DIRECTIONS: From Phillips, proceed northeast on Route 142 in the direction of Kingfield. At approximately 1mile, park near the bridge over the Sandy River. Walk through the community park to the river outcrops above and below the bridge. PLEASE DO NOT COLLECT SAMPLES FROM THIS SITE.
The river runs over granite, both coarse- grained and very coarse-grained (pegmatite). Its minerals include gray quartz, white feldspar, black tourmaline, black and white micas, and pink garnet (FIG). Tourmaline, mica, and garnet, minerals rich in either aluminum and/or water, indicate a sedimentary source that was melted to produce the granitic magma. Downstream, several screens of metamorphosed sedimentary rocks further support a sedimentary parent.
The Phillips Granite, Katahdin Granite, and other Devonian granites of central and northern Maine signify the continent-continent collision between Avalonia and Laurentia (STAGE IV-B). The continental plates overlapped such that continental material, including abundant sediments, was buried, warmed, and melted. Some of these granites are comparable to tourmaline granites recently produced in the Himalayas by the India-Asia collision. Whereas some granites are hard, such as Katahdin and Mt. Desert Island, most granites are soft because there is very little holding the crystals together. Hence, they tend to control topography, forming basins surrounded by the hard ridges of rocks metamorphosed by heat from the granites. The Bigelow Range is a classic example of a metamorphic aureole flanking the granite making up Flagstaff Lake (FIG).
Directions: This site is considerably off the main route. Great Pond is located south of the Stud Mill Road east of Old Town. In the northwest corner of Great Pond Township, a road bears south from the Stud Mill Road. After crossing Dead Stream, you will pass boulders of red sandstone. Alternatively, the road passing just west of Bear Den Hill in T32 MD traverses outcrops of the red sandstone.
Dominantly sandy sedimentary rocks near Great Pond, near Eastport, in the Trout Valley area of Katahdin, and near Mapleton were deposited by rivers in a terrestrial environment. Their red color indicates oxidizing conditions. In the latter two locations they contain plant fossils (FIG). They were deposited on top of various folded and faulted rocks (stops 1-26).
The Great Pond and similar terrestrial deposits signify an end to marine conditions due to the preceeding continent-continent collision. The demise of the Iapetus Ocean coincided with the assembly of the supercontinent Pangea (STAGE IV-C).
