Say Goodbye to Graptolites...

Graptolite fossils from Presque Isle

It's hard to get sentimental about graptolites. The fossil of what's actually a colony of tiny animals looks more like a small saw blade than anything you might start a preservation campaign for.  It's probably for the better, too. A successful "Save the Graptolites" crusade would have preserved a world where reptiles and pine trees would never have thrived. In Silurian era Presque Isle, however there would have been no need to improve conditions for graptolites. They were already perfect.  

In a low outcrop not far from downtown Presque Isle, the pale rock feels gritty, but not coarse. This type of sediment is not the product of a deep ocean or a beach, but the sweet spot in between.  It's born in an area where prevailing winds could blow off the warm top layers of an ocean, and reveal the cold nutrient rich waters below.  Perhaps inconsequential to you or me, but life changing to a graptolite.

Certain shards of the rock slab host the shallow impressions of graptolite rhabdosomes, basically an apartment building for tiny animals called zooids.  In Silurian time the complexes either rooted themselves in coastal sediment or floated in masses at the surface.  The zooids may have reached out of the many holes in these colonial homes to grasp at and eat phytoplankton from the coastal waters, enriched by the upwelling of vital nutrients.  

In a time when Caribbean-like islands stood sentry on the coast of North America habitats like this would have been commonplace in Maine. But, Maine was changing. Three hundred eighty million years ago the tectonic block that serves as our current coast, Avalon, docked with Maine. The conjunction crumpled the graptolites' ocean habitat.  Driving fossil types of graptolites from fourteen  in the Silurian to one after the collision. Eighty million years later the jaws of Pangea snapped shut.  The huge landmass was inhospitable to the aquatic creature and by the time it had formed the graptolites were extinct.

The watery Silurian period was ideal for graptolites. The changing environment drove them out of Maine, and then to extinction.  A sad moment, perhaps. But, the transition to dry land had some advantages, too.  Plants left the coasts, invading Pangea, and in the process became trees. Amphibians bravely abandoned their shrinking watery habitats and evolved into reptiles. Graptolites didn't make it, but maybe that's okay. Perhaps their loss is our gain.

Dickson, Lisa, and Robert D. Tucker. Maine's Fossil Record: The Paleozoic. Augusta, ME: Maine Geological Survey, Dept. of Conservation, 2007. Print. 

Koren', T. N., and R. B. Rickards. "Extinction of the Graptolites." Geological Society, London, Special Publications (1979): 457-66.

"Graptolites." Common Fossils of Oklahoma. Sam Noble Museum. Web. 20 Dec. 2014.

Tipping the Clown: Changing Density in the Deer Isle Granite

When I was young I had an inflatable clown with weights on the bottom, so you could administer whatever childhood battering you cared to, and the clown would bob back upright.  I recently read about a feature of the Deer Isle Granite that got me thinking about that clown.

Deer Isle Granite: Naskeag Point

The granite that underlies Deer Isle is long.  It extends from Flye Point on the Blue Hill Peninsula to the southern tip of Stonington in the south.  While the rock is all clearly Deer Isle Granite, it is not homogenous.  Going to Naskeag Point on the mainland presents a deep pink, while a visit to Stonington displays a much wanner stone.  The middle ground of Oak point shows something in between.  The source of the redness may lie in oxidized (rusty) iron that replaces aluminum ions typically present in a mineral called feldspar.

Deer Isle Granite: Oak Point

Liquid rock under the surface cools to form solid granite.  As a result of 4.6 billion years of sorting by density, most granite bodies tends to have fairly uniform consistency.  Deer Isle Granite is different.  For some reason, during its formation, two types of magma were mixed together.  Imagine a nice Italian dressing, shaken before being added to salad. The vigorous mixing swirled everything together, but before it could harden there was time to settle.  Less dense materials, high in silicon content drifted to the top, while the more dense, high aluminum content stuff sank to the bottom.  The aluminum portion took on its iron and its rusty hue.

Deer Isle Granite: Stonington

Under normal conditions the weighted bottom of the clown would remain pointed downward.  The Acadian mountain building event was not normal conditions.  A small continent, and the tectonic plate it rode upon, glided across the fluid mantle toward the prehistoric Maine coast and rammed the landmass.  The collision was not a child's smack, but a match full of heavyweight boxer's jabs.  This impact was enough to permanently tip the clown on its side, revealing the changing color.

Dietrich, Richard Vincent, and Brian J. Skinner. Rocks and Rock Minerals. New York: Wiley, 1979. Print.

Hooke, Roger Leb.. "A Geologic History of Deer Isle, Maine." College of the Atlantic, Serpentine Ecology Conference. July 2007. Web. 14 Oct. 2013. <www.coacommunity.net/downloads/serpentine08

How to Make Bricks in Three Easy Steps

Last weekend my son and I foresook our weekly grocery shopping trip at the West Falmouth Hannaford.  Instead we crossed the bridge on the south end of the parking lot and ended up taking a walk on an ancient sea floor.  Don't get me wrong, this is not a magical bridge that can transport one to a fantasyland.  The bridge was built in 1859 by the railroad company to connect the Hobbs farm to the rest of society.  John Hobbs homesteaded the land in 1775, and before 1859 when the railroad isolated it and the Hobbs sold it, put it to a variety of industrious uses.  Like people of earlier times are fabled to have done, the Hobbs put every part of the land to use.  The trees became oak shingles, the soil was farmed and the clayey sediment was extracted to make bricks.  The story of these bricks extends far beyond the Hobbs enterprising spirit and thousands of years before the clay was first dug.

The story of our bricks began about 22,000 years ago when glaciers covering much of the globe decided to call it a day and begin the slow commute home from Long Island, New York (Long Island formed as the flowing ice of the glacier delivered gigantic piles of rock to its melting endpoint).  At this point, Maine and the rest of northern North America were buried in ice. Heavy, heavy ice.  The normally firm raft of rock, on which our continent sits, sank like a rowboat upon boarding.  As melting glaciers contributed to a growing ocean, this depressed plate would make way for the intrusion of a sea much larger than today's Atlantic.

The land above the sea couldn't wait to cast off its icy water.  Massive streams poured tons of melted ice into the growing sea, but the water didn't come alone. As the rivers raced to the sea their fast current picked up every stone, pebble, sand grain or mote of clay they could carry.  Massive material, like stones and pebbles may have been dropped long before reaching the sea.  When the stream met the water, it rapidly decelerated. Upon slow down, enough sand was dropped to create a river delta as deep with sand as a football field is long.  The sand from this river's mouth can still be spied along I95 between Gray and Lewiston and is currently being quarried in Gray.  But what about the bricks?

The slow moving water, at this point, would have dropped nearly everything.  Robbed of most of its energy by the trudge into the ocean, the sluggish water couldn't carry much.  Luckily, clay is small and light.  The water transported these small grains the farthest, finally dropping them at the sight of the future Hobbs' farm.  About 13,000 years ago, with the weight of ice removed, the plate rebounded, and the sea level dropped.  The acreage of the Hobbs' farm was revealed.  Soil developed.  Oaks grew.  Eventually, the Hobbs would dig up their bricks and my son's and my weight would leave footprints in the ancient seabed.  

McCully, Betsy. "Ice Age." New York Nature. N.p., n.d. Web. 11 Feb. 2014. <http://www.newyorknature.net/IceAge.html>.

Robinson, Michael A., Stewart K Sandberg, and Kirkpatrick Melissa D.,. "Using transient electromagnetic soundings to map the thickness of the Gray Delta, Maine, and correction of data using coil calibration to improve resolution. ." Geological Society of America Abstracts with Programs 33.1 (2000): 1. Print.

Weddle, Thomas K., Gray Quadrangle, Maine, 1:24,000, Augusta, ME: Natural Resources Information and Mapping, Maine Geological Survey, 1997.

"Surficial Geologic History of Maine." Maine Geological Survey. N.p., 6 Oct. 2005. Web. 11 Feb. 2014. <http://www.maine.gov/dacf/mgs/explore/surficial/facts/surficial.htm>.

"River Point Conservation Area." The Town of Falmouth . The Town of Falmouth , n.d. Web. 11 Feb. 2014. <http://www.town.falmouth.me.us/pages/falmouthme_parks/trailmaps/RiverPoint>.

Maine's Pinatubo: Unearthing a Natural Disaster

Soon J.D. Irving Limited may be freed to start thinking about how to take 22 million tons of copper ore out of the ground in northern Maine. The Maine legislature may relax laws regulating the mining of metals in Aroostook County. While Irving consider strategies for extracting copper and zinc, as well as relatively small amounts of gold and silver, I have been thinking about how the metal rich rock, called sulfide ore, got there in the first place. It all occurred about 500 million years ago when a series of islands, not too unlike the Philippine islands, were forming off the coast of North America.

The best lens from which to consider what went into creating the ancient ore might be to consider a more recent event. Twenty-one years previous to the bill being passed, Mount Pinatubo was cooling off after a long summer of letting off steam. In the summer of 1991, the Philippine Sea Plate subducted beneath the Eurasian plate, releasing 10 billion tons of magma in a volcanic eruption. As the magma neared the surface, it released chemicals that refused to join with others to form minerals. Valuable metals, like zinc and copper and dangerous ones like cadmium and lead, were distributed as ash across the Philippine region. Far from a rain of wealth, the ashfall is thought to have significantly shortened human lifespan on nearby islands. Sulfur combined with oxygen in the atmosphere to form sulfur dioxide gas, which in turn joined with moisture in the atmosphere to form sulfuric acid. Aircraft throughout the Northern Hemisphere experienced corrosion damage from the acid for years afterward. It is with good reason that the eruption of Mount Pinatubo was regarded as a natural disaster.

Five hundred million years ago no one was around to experience the ash or acidity of eruptions that formed the islands that would become the metal-rich rock in northern Maine. The islands and the ore formed as two oceanic plates in a proto-Atlantic ocean collided. One plunged beneath, bringing loads of ocean water with it. As the water and the rock descended, both heated. The water would have rushed through subterranean rock, dissolving unmatched elements along the way. The scalding liquid would have picked up sulfur, then metals. It would wend its way upward, cooling as it went. As its temperature dropped the dissolved sulfur, submerged and lacking its partner oxygen, would seek out other mates, finding them in the unmatched metals that flowed alongside. The sulfur/ metal pairs, sulfides, solidified and were stored underground preventing life's exposure to corrosive acids or dangerous metals.

In the next decade J.D. Irving may decide it is worth unearthing the metal-bearing sulfides of Aroostook County. But the price of digging up a natural disaster must be paid. Payment can be rendered in advance if the mining company works to prevent the spread of sulfur and metals into the environment. It can be paid after the fact by the citizens of Maine, in the form of clean up costs. Or, it can be paid by sacrificing the beauty and balance of northern Maine's natural ecosystem. Regardless, the cost must be rendered, and it's best to consider this before the bill comes due.

Beck, Fredrick. "A History of Non-Ferrous Metal Mining and Exploration in Maine." Geological Society of Maine. N.p., n.d. Web. 1 Jan. 2014. <http://www.gsmmaine.org/wp-content/uploads/2010/02/Beck-A-History-of-non-ferrous-metal-mining-and-exploration-in-Maine.pdf>.

Casadevall, Thomas J. , Perla J. Delos Reyes, and David J. Schneider. "The 1991 Pinatubo Eruptions and Their Effects on Aircraft Operations." Fire and Mud: Eruptions and Lahars of Mount Pinatubo. U.S. Geological Society, 10 June 1999. Web. 1 Jan. 2014. <http://pubs.usgs.gov/pinatubo/casa/>.

"Environmental Health and Safety Guidelines Base Metal Smelting and Refining." International Finance Corporation. International Finance Corporation, 30 Apr. 2007. Web. 1 Jan. 2014. <http://www.ifc.org/wps/wcm/connect/4365de0048855b9e8984db6a6515bb18/Final%2B-%2BSmelting%2Band%2BRefining.pdf?MOD=AJPERES&id=1323152449229>.

"Open-pit Metal Mining in Maine." Natural Resource Council of Maine. Natural Resource Council of Maine, n.d. Web. 1 Jan. 2014. <http://www.nrcm.org/issue_mining.asp>. 

"Volcanic Gases and Their Effects." Volcano Hazards Program. U.S. Geological Survey, n.d. Web. 1 Jan. 2014. <http://volcanoes.usgs.gov/hazards/gas>. 

"Volcano or Environmental Disaster?." VolcanoCafe. N.p., 18 Nov. 2013. Web. 1 Jan. 2014. <http://volcanocafe.wordpress.com/2013/11/18/volcano-or-environmental-disaster/>.

The Outcrop in the Crystal

It's my 20th post!  This blog post is the first of several that will highlight an outcrop that drove my interest in Maine geology.  If you're looking for the outcrop it's on Rte. 115 on the Gray/ Windham border.  Or check it out on the Sphere app.  

The outcrop told the story of Maine.  The white rock, a granite, bubbled up when Africa's coast collided with our own 450 million years ago, sealing Maine into the Pangeaic interior.  The black basalt resulted from one of the volcanoes that once again cleaved the supercontinent in two when Pangea split.  The glittery schist told the tale of a muddy ocean bottom that predated both two igneous rocks.  But how did the green rock get there?

There were obvious clues.  The parallel stripes of white, green, and sometimes even gray told tales of piling layers.  The fact that these layers took turns with schist, a mudstone altered by heat and pressure, as one scanned the outcrop from left to right suggested that it, too, formed in that muddy sea.  Other facts didn't add up.  The tough rock scored glass.  Most of the usual sedimentary suspects wouldn't do that; unmetamorphosed mudstone and limestone were just too soft.  Their metamorphic progeny, schist and marble would have crumbled as well.  Sandstone, and its postbear quartzite, would do the job, but the look wasn't right.  The rock lacked the granularity of sandstone, and the sugariness of quartzite.

The truth became clearer as I began to research Silurian time, a period between 416 and 444 million years ago, in which the green rock formed.  The ocean bottom that it gathered in was flanked on three sides.  To the north lie North America, to the south, a hunk of land that would become Maine's coast. To the east, Western Europe plugged another opening preventing the flow of currents.  The phlegmatic basin, just south of the equator, became poor in oxygen, but rich in life.  Lacking our usual breath of life, the creatures of the sea resorted to extreme measures - consuming sulfur.  

The chemistry of this bounded sea played an important role in the green rock's formation.  As a coral reef, in an aerated ocean, degrades, it forms limestone, which is composed of the elements calcium, carbon and oxygen.  Our sluggish sea would have produced a similar product, with one small difference: the sulfur consumption exchanges some of the sediment's calcium for a new element - magnesium.  The rock it forms goes by a different name: dolomite.

Even dolomite doesn't have the strength to scratch glass.  The rock would require one final transformation.  As plates moved, the basin grew smaller, and then disappeared.  The formation of Pangea spurred an influx of fluids: some large, like the bulb of magma that formed the white granite, some less immense, like the infusion of quartz and water that flowed through the ancient ocean bottom.  This liquid sought out any channel it could access, including spaces in the schist, and the dolomite.  The schist proved passable, but inert.  The dolomite was reactive.  The heat and chemicals in the flowing fluid released carbon and oxygen from the dolomite (as carbon dioxide).  Some of the quartz stuck around, providing the white layers of the rock.  The green crystals, a mineral called diopside, kept the calcium and magnesium of the dolomite and replaced the CO2 with silicon and oxygen from the quartz.  

The outcrop is a testament of Maine's geological history.  It documented the marine roots and the accordion push-pull of continents.  The green diopside crystal, a fractal of that outcrop, records the deoxygenated ocean bottom in its calcium and magnesium.  It further tells the tale of the pushing and pulling continents in its silicon and oxygen.  The green crystal, a mere fragment of the outcrop, tells the outcrop's entire story.

Bickle, M. J. , H. J. Chapman, J. M. Ferry, D. Rumble, and A. E. Fallick. "Fluid Flow and Diffusion in the Waterville Limestone, South—Central Maine: Constraints from Strontium, Oxygen and Carbon Isotope Profiles." Journal of Petrology 38.11 (1997): 1489-1512. Print.

Ferry, J. M.. "A Comparative Geochemical Study Of Pelitic Schists And Metamorphosed Carbonate Rocks From South-central Maine, USA." Contributions to Mineralogy and Petrology 80.1 (1982): 59-72. Print.

Fischer, Dan , Tammy (Yue) Liu, Emily Yip, and Korsen Yu. "The Silurian Period."The Silurian Period. University of California Museum of Paleontology, 5 July 2011. Web. 6 Dec. 2013. <http://www.ucmp.berkeley.edu/silurian/silurian.php>.

Hussey, Arthur M., II, 1996, Bedrock geology of the North Windham 7.5' quadrangle, Maine; Maine Geological Survey (Department of Conservation), Open-File Report 96-16, 6 p.

Helmholtz Centre for Ocean Research Kiel (GEOMAR) (2012, June 7). How does dolomite form?. ScienceDaily. Retrieved December 8, 2013, from http://www.sciencedaily.com/releases/2012/06/120607105815.htm

Wilde, Pat , William Berry, and Mary Quinby-Hunt. "Silurian Oceanography."Marine Sciences Group. University of California, Berkeley, n.d. Web. 8 Dec. 2013. <http://www.marscigrp.org/sil91.html>.

A Tale of Two Conglomerates: Chapter 3

This is Chapter 3 of a 3 part blog post.  Click here to read part 1 or here to read part 2.

Chapter 3: Metamorphism
When we last left our conglomerate heroes Mount Battie was hanging out around the South Pole, and Mars Hill near the equator.  As you can probably guess they didn't stay put.  Mars Hill and what is called the Laurentian Continent sped north, but Mount Battie and the Avalonian microcontinent sped faster.  The result: a Mack truck v. Geo Metro collision of geologic proportions (in other words, incredibly powerful, and extremely slow).  This last segment of the post is the claims adjuster's report, with metamorphism in the rocks marking the damage.

Metamorphism is a process in which rocks are changed by heat and pressure, and the Midcoast certainly endured both during the collision.  Before the collision, the sandstone that made up both the clasts, and the matrix, would have been indiscernible from sand except for the fact that the sand was cemented together into a rock.  After the collision geologists find a set of minerals called amphibolite.  Unable to form under different conditions, amphibolite tells our adjuster that the collision caused a pressure equivalent of between one and six of those Mack trucks resting on every inch of rock, while the temperature rose to around 1000 degrees fahrenheit.  Under these conditions a literal Geo Metro would be obliterated.  Our figurative car is merely transformed.  The heat and pressure of the continents colliding is enough to recrystallize the sand - converting them from discernible grains into an interlocking mass, which is called quartzite.

This is not to say that the Laurentian truck did not take damage.  Androscoggin County endured an equivalent amount of metamorphism.  But if the Midcoast and Androscoggin County were the respective front bumpers of our Metro and our Mack Truck then Mars Hill is the back end of the truck, experiencing little damage.  The clay particles in the shale clasts, under similar conditions to Mount Battie, would have recrystallized.  This would have made the pebbles look like miniature disco balls, called schist, within their matrix.  Limestone can endure a lot of heat. The limestone matrix may have remained limestone, however, it is also possible that other materials like quartz may have been injected through the rock.  In this scenario quartz, or silica, replace some of the elements in a calcium carbonate limestone creating what is called a calc-silicate rock. Instead, what we are left with looks like what we started with a mixture of limestone mud and pieces of rock all piled together heated scarcely above the temperature necessary to turn the amalgamation into stone.

Bartok, Peter. "Geology of Ireland and the United Kingdom." Ireland and United Kingdom. Tarryton, NY: Marshall Cavendish, 2010. 15-16.

Mottana, Annibale, Rodolfo Crespi, and Giuseppe Liborio. Simon and Schuster's Guide to Rocks and Minerals. Ed. Martin Prinz, George E. Harlow, and Joseph Peters. New York: Simon and Schuster, 1978. Print.

"How Much Does a Mack Truck Weigh?" Ask.com. Web. 03 July 2013.

"Maine Geologic Map Data." Maine Geologic Map Data. 05 Apr. 2013. Web. 03 July 2013.

A Tale of Two Conglomerates: Chapter 2

This is Chapter 2 of a 3 part blog post.  Click here to read part 1.

Chapter 2: The Matrix
Conglomerates share there stories in several ways.  The pebbles that fall together to make the rock tell a story of what came before.  The stuff that holds the rock together - the matrix - speaks about what was happening when the rock came together.

Four hundred and fifty million years ago, Mars Hill would have been pretty close to the Equator.  This time period also happened to be when coral were distributed widely around the world.  These facts were unknown to me at the time I first visited Mars Hill.  What I did know, however, was that Mars Hill was not far from a town called Limestone.  I looked at those clasts, and I looked at the stuff that held them together (called the matrix in the geology world), and I wondered.  I have since broken my piece of conglomerate and, logically, dropped it in vinegar.  The neat thing about limestone is that you don't have to wonder for long.  Dropping limestone in vinegar causes a reaction between the acetic acid of vinegar and the limestone base, causing carbon dioxide to fizz off.  Soon after the rock hit the bottom of the mug, bubbles started rising to the surface of the vinegar.  Four hundred and fifty million years ago, about the same time that ocean bottom rock was being torn apart, a coral reef, not far from Mars Hill was breaking down as well.  While the majority of this calcium carbonate piled up on flat ocean bottom, creating the substrate for Aroostook County's potatoes, some followed the flow of water over some sort of cliff into some kind of deep water canyon allowing shale pebbles and limestone mud to mix together.

The pebbles that make up the Mount Battie conglomerate are held together by something else.  500 million years ago, Mount Battie was in a part of the world not very likely to host coral.  The Avalonian microcontinent, perhaps similar in form to today's Japan, was on the bottom part of the world, below the 60th parallel.  The matrix here, insoluble in acid, is quartzite, indicating a sandy environment.  Layering at the site indicates the sand gathered in an ocean basin, where wave action swept away most of the smaller sediments, leaving behind sandstone pebbles in a matrix of sand.  This shore line would have been a bit cold for developing coral reefs, excluding the development of limestone in the area.  This gravelly beach the stage for our future coastal mountain.      

Modern World Coral Reef Locations - Credit: NASA

Berry, Henry N., IV. "The Bedrock Geology of Mount Battie, Camden." Maine Geological Survey: , Maine. Maine Geological Survey, 19 Apr. 2012. Web. 01 July 2013. <http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/sites/jul01.htm>.

Scotese, C. R. "Earth History." Plate Tectonic Maps and Continental Drift Animations. PALEOMAP Project. Web. 01 July 2013. <http://www.scotese.com/earth.htm>.

Wang, Chunzeng, Gary Boone, and Bill Forbes. "Geology of Mars Hill Mountain and Vicinity." Http://goaroostookoutdoors.com/. Web. 1 July 2013. <http://goaroostookoutdoors.com/sites/default/files/trails/maps/mars_hill_geology2.pdf>.

Maine's Earthquakes

Today there was a small earthquake about 7 miles from Augusta Maine.  The quake was a 2.6 on the Richter Scale.  Because the Richter scale is logarithmic, each point it rises means the quake is 10 times stronger.  By extension, this quake was about 100 times gentler than the 4.5 that many of us in southern Maine felt last October 16th.

We're used to hearing about big earthquakes: The 2010 Haiti earthquake (7.0), the 2011 Japan earthquake (9.5, 10,000,000 times as powerful as the one felt today) or the ones that occur along the San Andreas in California.  All of these occur on active plate boundaries where one plate is shoving under or, in the case of California, past another, but what's happening in Maine?  There haven't been any active plate boundaries in Maine for more than 200 million years.

If you could look at Maine's Carfax report it would not look good.  Maine is the victim, nay product, of several collisions with other landmasses.  Each one left Maine with several small faults, where the old continents docked.  Then there was the stretching.  When Pangaea split the continent spread to fill up the old space.  Some parts of once solid rock sank down, while others remained aloft.  The result: despite it's beautiful exterior, our state has some pretty severe internal damage.

There are faults on the surface within 15 miles of today's earthquake, but the earthquake occurred 3.1 miles underground.  It's difficult to assign blame for the earth shift that occurred, but we can be assured that it is a result of Maine's storied tectonic history.

"Central Maine Feels 2.6 Magnitude Earthquake." Bangor Daily News. 21 June 2013. Web. 21 June 2013. <http://bangordailynews.com/2013/06/21/news/state/central-maine-feels-2-6-magnitude-earthquake-sidney/>.

"M2.6 - 2km W of Sidney, Maine." Earthquake Hazards Program. United States Geological Survey, 21 June 2013. Web. 21 June 2013. <http://earthquake.usgs.gov/earthquakes/eventpage/usc000hx15#summary>.

"Maine Earthquakes 1997 to Present." Maine Geological Survey. State of Maine. Web. 21 June 2013. <http://www.maine.gov/doc/nrimc/mgs/explore/hazards/quake/quake-recent.htm>.