|Aww...Schist. The sparkly covering on this rock is|
ancient ocean bottom heated in a continent colliding oven.
|Quartzite Revealed. Notice the blockier texture on the |
bottom half of the rock. There is a thin layer of schist
below the quartzite,
So what brings the unmoving abyss of the ocean bottom next to the active coast. One possibility is time. Sea level has fluctuated throughout geologic time. To whit, the Hannaford in West Falmouth was built on ocean bottom from the ice age, and taking I-95 north of Gray reveals sandy roadsides that may be beaches of the same time period. This sort of shift in water level is certainly capable of creating a rock that transitions from mudstone to sandstone and back again, or post crushing, a quartzite sandwich, with schist bread.
But there is another possibility. The Carrabassett Formation, out of which the north half of Ira Mountain has been cut, is known for its turbidites. Imagine an underwater ridge. The top of the ridge, exposed to the movement of waves and the final surges of upland streams, plays host to hefty sediments like the aforementioned sand. The bottom of the ridge, protected from the rigamarole, cradles the tiny clays. Then something happens. A stream changes course. A rogue wave mixes things up. The ridgetop sediments, perhaps already precariously perched, fall down. The movement stirs up everything, creating a stew of water, sand and clay. As time passes the turbid water clears again, first dropping the heavy sand, then setting down the lighter clay. This process would repeat again and again over the life of the ocean and the ridge until these layered sediments became stone.
Which of these possible histories is true is unclear. Maybe this detail of the story is unwritten, or maybe I just haven't learned how to read this piece of the language. It is the hope that we might know more, that there is some unwrapped gift, that keeps me looking and keeps me learning.
Adams, Dennis. "About Beach Sand."Beaufort County Library. Beaufort County Library, Web. 14 Aug. 2013. <http://www.beaufortcountylibrary.org/htdocs-sirsi/beachsan.htm>.
Dorais, Michael J., Robert P. Wintsch, Wendy R. Nelson, and Michael Tubrett. "Insights Into The Acadian Orogeny, New England Appalachians: A Provenance Study Of The Carrabassett And Kittery Formations, Maine." Atlantic Geology 45 (2009): 50-71.
Hanson, Lindley . "The many expressions of a New England formation." Vignettes: Key Concepts in Geomorphology. SERC, Web. 15 Aug. 2013. <http://serc.carleton.edu/vignettes/collection/25133.html>.
Schieber, Jürgen . "Sedimentary Structures." Indiana University. Indiana University, n.d. Web. 15 Aug. 2013. <http://www.indiana.edu/~geol105/images/gaia_chapter_5/sedimentary_structures.htm>.
Weller, Roger . "Schist Photos." Virtual Geology Museum. Cochise College , 24 May 2013. Web. 15 Aug. 2013. <http://skywalker.cochise.edu/wellerr/roc