The Trout Valley Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Maine Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

Description

Situated in north-central Maine, the Trout Valley Formation is located in a fault-bounded basin. An erosional unconformity separates it from underlying felsites. The formation exists entirely within the confines of Baxter State Park, and collecting of materials without authorization is prohibited. The formation represents an alluvial fan draining an active volcanic source and has a basal cobble conglomerate, consisting only of rounded fragments of the underlying volcanic

felsite Felsite is a very fine-grained volcanic rock that may or may not contain larger crystals. Felsite is a field term for a light-colored rock that typically requires petrographic examination or chemical analysis for more precise definition. Color ...

, known formally as the Traveler Rhyolite. The conglomerate is overlain by sandstone, which contains lenses of gray shale,

black shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...

and fine conglomerate, in a generally fining-upward sequence. The unit's distal portions terminate in tidal mudflats, which have produced a bivalve-dominated fauna that also yielded the first relatively complete

Eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 Myr, mil ...

found in northern New England. The Trout Valley Formation also contains fossilized

Psilophyton ''Psilophyton'' is a genus (biology), genus of extinct vascular plants. Described in 1859, it was one of the first fossil plants to be found which was of Devonian age (about ). Specimens have been found in northern Maine, USA; Gaspé Bay, Queb ...

plants, as well as a number of other taxa, including ''Pertica quadrifaria'', the official state fossil, the tallest plant of its age known from anywhere in the world. The Trout Valley Formation earlier was dated to the Early Devonian by the presence of fossilized

eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct marine arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period, 467.3 Myr, mil ...

scales, possible estherids and ostracods, but is now assigned to the early Middle Devonian (Emsian); it is believed to be 3-5 million years older than the

Gilboa Fossil Forest Gilboa Fossil Forest, New York, United States, is a petrified forest and one of the oldest known forests. Located near the Gilboa Dam in Schoharie County, New York, the region is home to tree trunks from the Devonian period. The fossils, some of ...

of New York. In contrast to the Traveler Rhyolite and sandstones beneath the Trout Valley Formation, which have open folds, the formation itself is unfolded. However, normal bed-parallel faulting within the sandstones suggest that uplift may have been taking place during deposition. This suggests that the Trout Valley Formation was deposited after the tectonic activity that altered the underlying rocks, but before that which uplifted the mountains in this area had come to completion. Although the

Katahdin Pluton Mount Katahdin ( ) is the highest mountain in the U.S. state of Maine at . Named Katahdin, which means "Great Mountain", by the Penobscot Native Americans, it is within Northeast Piscataquis, Piscataquis County, and is the centerpiece of Ba ...

cuts through the Traveler Rhyolite, granitic fragments from the Katahdin Pluton have never been found in the Trout Valley Formation. At least one minor dike of Traveler Rhyolite has, however, been found cutting through the rocks of the Trout Valley Formation.

References

* * Devonian Maine Devonian southern paleotemperate deposits Geologic formations of Maine {{Maine-geologic-formation-stub

Description

See also

References