Monday, March 25, 2019

Geology of the National Parks Through Pictures - DeSoto National Memorial

My next post about the Geology of the National Parks Through Pictures  from a recent trip to visit my mother in Florida. I managed to convince the family to hit up the nearby national park. 

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website


DeSoto National Memorial

 The obligatory entrance sign with my Gummy Bear.

 The park sits at the mouth of Tampa Bay along the south shore of the Manatee River. This is an estuary environment where the salt water from the Gulf of Mexico mixes with the fresh water from the Manatee River.

The ecological environments within this small park range from beach front dune to mangrove swamp.

 But with many archeological parks, one of the primary geological aspects are the building stones used to make the dwellings. Here we have the remains of the "Tabby House". Tabby is a building stone made from the mixture of oyster shells, lime, sand, and water creating a hardened stone brick over about three days. The bricks were then coated in a plaster of lime, sand, and water.

 A view over DeSoto Point overlooking the Manatee River.

 Here is a shell midden, which is essentially a garbage pile of discarded remains of mollusks, shellfish, and bones. You can see within this midden the rather large gastropod (snail) shells.

 Another geological aspect commen in many parks are the building stones used in monuments. Here is a view of the Holy Eucharist Monument. The base of the monument is limestone cut in Mankato, Minnesota. The limestone in use is the Ordovician age Kasota limestone, which is actually a dolomitic limestone, part of the Oneota dolomitic strata. The color of the stone is known as a "buff color" which is that slightly reddish-brown color due to the 1% iron oxide composition providing a rust staining to the stone. Although the Kasota does not have many fossils, it does have a significant number of traces fossils running through the rock, however I am not certain the type of trace fossils preserved.

The carving stone came from Madrid, unfortunately I cannot find any information about the type of stone used, nor did I take any better pictures or get a closer look at the stone to determine for myself.

 Taking a stroll though the dense beach forest.

 The Desoto Trail marker, using "granite" from an unknown location.

A closer view of the "granite", but based on this picture it may more accurately be described as a diorite, however I don't recall what type of rock it was from my visit.


Friday, March 22, 2019

Geology of the National Parks Through Pictures - Canaveral National Seashore

My next post about the Geology of the National Parks Through Pictures is about a park visited a long time ago.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website


Back a long time ago during a Spring Break trip of 2003, my girlfriend (at the time) and I hit up the Canaveral National Seashore. And although the pictures taken at the time weren't geologically inclined, there is still geology that abounds. The seashore is made up of several geological features, mainly a barrier island beach and the sheltered lagoon, which provides an safe space for the wildlife in the region, properly termed an estuary. 

The barrier island, as seen here with me attempting to enter the Atlantic Ocean, is a protective sand beach environment that breaks up the waves before they can hit the mainland. This beach, detached from the mainland, is created by the inward movement of the waves interacting with the outward movement of the waves, also known as the riptide. At this location where the waves interact, the ability of the water to carry sediment out to sea is reduced and the sand drops to the ocean floor. Over time this sand piles up, eventually becoming an island strip that acts as a barrier to the ocean waves and provides a safe and quiet lagoon between the island and the mainland. Canaveral National Seashore provides 24 miles of undeveloped beach, the longest continuous stretch in all of eastern Florida.

Although not directly geological, as a paleontologist I am also a biologist at heart and so the ecology, the fauna, and the flora of different parks also interests me. Here we have several instances of the fauna of the park with the first being an armadillo. We actually encountered quite a few of these guys, much more than I had ever seen before or since.

Checking out the beach at night allowed me to find some crabs scuttling along.

And some of my favorite wildlife, the manatees. The lagoon provides a perfect habitat for them, protecting them from the strong ocean waves and providing them with a redible supply of food.

Monday, March 11, 2019

Geology of the National Parks Through Pictures - The Washington Monument

My next post about the Geology of the National Parks Through Pictures is about some parks visited a long time ago within Washington D.C.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website


 View from Arlington National Cemetery. Like many of Washington D.C.'s monuments and memorials, there are multiple stones that were used for the construction of the Washington Monument.

1. Underneath it all is the foundation, which is comprised of the District's official rock, the Potomac Bluestone. Potomac bluestone is a more archaic term of the rock unit currently known as the Sykesville Formation, a formation that has had numerous designations over its history. The Sykesville Formation is identified as a metagreywacke, which is a metamorphosed greywacke. This type of rock is a poorly sorted, course and angular grained, sandstone or conglomerate. Greywackes typically are formed in the deep marine from strong turbidity currents (underwater landslides). The metagreywackes of the Sykesville Formation contain various degrees of metamorphism and in many places original sediment and sedimentary structures can still be identified within the rock unit itself. The earliest stones quarried by settlers of the region were the schists and gneisses of the Piedmont, known locally as this Potomac Bluestone. The Potomac Bluestone, or Sykesville Formation, lies towards the northwest of Washington D.C., crossing the Potomac River. This region contains many heavily metamorphosed and faulted rock units and these rocks are thought to have been metamorphosed from Neoproterozoic to Early Cambrian diamictites and sedimentary melanges, which contained a wide range of rocks. The Sykesville Formation was likely being metamorphosed from the Ordovician into the Silurian. The rock itself is a light- to medium-grey medium-grained metagreywacke melange consisting of a quartz, feldspar, and a large mixture of pebble and boulder sized chunks of unmetamorphosed rocks (termed olistoliths). The Sykesville has a fracture pattern along the foliation plane and two mutually perpendicular joint sets. This fracture pattern results in the landscape breaking into a series of pyramidal protrusion that aided in the the use as an early building stone for the District. Quarries along Rock Creek and Little Falls in Maryland provided Sykesville blocks for many early Washington D.C. projects.

 2. The outer layer of the Washington Monument is constructed of three different types of marble. The bottom 152 feet are built with "Texas Marble", named for the quarry in which it was mined in Texas, Maryland. However, the geological name for the marble is the Cockeysville Marble. The Cockeysville Marble is Late Precambrian (~600 million years old) in age and has many variations and layers within it making individual quarries of the marble contain significantly different rock types. The variations within the marble amount to differences in the amount of magnesium within the rock, where some areas have a metadolostone (high Mg content) versus a metalimestone (high Ca, low Mg content) varieties of marble. The Texas Quarry produces a course-grained marble that is a nearly pure calcitic marble (a high Ca metalimestone).

Following the initial portion of construction (1848-1854) the funds ran out for the project and the monument construction was stopped. This is where the color change takes place.

View across the Tidal Basin.

3. Construction resumed 25 years later after discovering the foundation needed to be increased and repaired. Four rows of new marble were then added to the monument above the Texas Marble. This marble is the Sheffield Marble from the John A Briggs' quarry in Sheffield, Massachusetts. A slight color change can be observed at this point, however since the layers are so minimal compared to the size of the monument, it may be unobserved. The Briggs' Quarry marble is geologically known as the Early Ordovician, Stockbridge Marble. The marble is a white calcite marble interbedded with light grey dolostone.

After significant delays and problems obtaining the Sheffield Marble, the contract was canceled and the builders went back to the original stone, or at least as close as they could get to it.

4. Above the color change line encompassing the upper 2/3rds of the monument is a repeat of the Cockeysville Marble, however this time it is quarried from the Beaver Dam Quarry in Cockeysville, Maryland. The Cockeysville mine is located 1.5 miles from the Texas, Maryland mine where the lower section of the monument's marble is from. When the monument was being constructed the marbles were nearly identical and therefore it was assumed that everything would match. However, weathering has treated the two marbles differently, despite being from the same formation and from nearly the same quarry. This is because of the heterogeneity of the marble listed above. The marble at Cockeysville is finer-grained and has a much higher Mg content, more akin to a metadolostone. The smaller grain size and the increase in magnesium content results in the weathering producing a slightly different color for the marble over time, a feature that is pronounced when displayed on the scale of the Washington Monument.

5. Behind the marble outer face are also multiple stones. One of the backing stones for the marble facade is red Seneca Sandstone. Geologically the red Seneca Sandstone is known as the Poolesville Member of the Manassas Formation. This is the same rock that was used for the construction of the Smithsonian Castle. The Manassas sandstone is part of a series of Triassic sandstone basins that extend from North Carolina to Massachusetts. These related rocks supplied much of the "brownstone" used in the NYC construction at the same time. The sandstone is primarily composed of quartz, alkali feldspar, and muscovite with ~5% Fe2O3 concentration, attributing to the strong rusty-red color.

6. Another of the backing stones is the Maine Granite, which is from a quarry on Mount Waldo, Maine. The geological name for the granite, is surprisingly enough, the Mount Waldo Granite. The granite is a Devonian Age (390 million years old) intrusive igneous pluton. The pluton intruded within tightly folded Precambrian and Lower Paleozoic age schists, gneisses, quartzites, and migmatites. The granite is light to medium grey, course-grained, and porphyritic, which contains the minerals microcline, plagioclase, quartz, and biotite. The granite deposit was studied as a potential place for a shallow underground oil repository, however documentation of severe rockbursts have prevented the unit from being used as such.

The third of the marble facade backing stones is the previously mentioned Potomac Bluestone, which was also used as the foundational rock.


Saturday, March 09, 2019

Geology of the National Parks Through Pictures - The Jefferson Memorial

My next post about the Geology of the National Parks Through Pictures is about some parks visited a long time ago within Washington D.C.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website


The Jefferson Memorial

View from the front (circa 1990). Like the Lincoln Memorial, the Jefferson Memorial is comprised of at least seven different build stones from across the country.

1. The memorial itself is constructed of white Imperial Danby marble from Vermont. Imperial Danby marble is actually the Lower Ordovician, Columbian Marble member of the Shelburne Formation. The Shelburne Formation includes three different rock units; the Sutherland Falls marble, the Intermediate Dolostone, and the Columbian Marble. The Shelburne Formation formed from the metamorphism of Cambrian to Ordovician age limestones that were metamorphosed during the Early Ordovician. Located on Dorset Mountain in Danby, the Danby Quarry is the world's largest underground quarry and is one of the largest producers of marble in the world. The Columbian Member is roughly 500 to 600 feet thick and is a white, massive, medium-grained marble that is composed primarily of calcite. There are also small instances of pyrite, chalcopyrite, muscovite, and chlorite that give the marble some green or dark streaks. The marble usually weathers white, but can vary to dark grey. Due to the strong similarities between the Sutherland Falls Marble and the Columbian Marble, it is often difficult to differentiate between the two, but unlike the Sutherland, contorted forms are not conspicuous within the Columbian and the markings usually have a linear pattern.

2. The dome is constructed of Indiana limestone, also known as the Salem Formation and also used in the Lincoln Memorial. The Salem Formation is a Middle Mississippian age (335-340 million year old) light-grey to bluish-grey pure calcarenite limestone that crops out between Bloomington and Bedford in the south-central portion of Indiana. Quarrying of the stone began in 1827 and has continued up to the present day with nine different quarries all mining the same formation. Indiana Limestone is a "freestone", which means that there is no preferential cracking, jointing, or splitting. This also means that blocks of the limestone can be planed, hand-worked, or otherwise manipulated without fear of the rock breaking in a preferential direction. The limestone is 97% pure calcite with microscopic foraminifera and bryozoan fossils found throughout.

View from the top of the Washington Monument.

3. The foundation and circular terraces are made from Georgia granite. Despite the enormous amount of data regarding almost any other piece of stone in this memorial, or most of the other Washington D.C. memorials, there isn't much information regarding which "Georgia granite" was actually used in the construction of the memorial. My assumption (and it is only an assumption) is that the granite in question is the Elberton Granite. Elberton Granite is a "monumental grade" granite, meaning that the granite has a "uniform texture and color, freedom from flaws and general suitability for polishing and carving as well as resistance to weathering". It is also one of the few granites to be actively quarried in Georgia during the 1930's, when the Jefferson Memorial was constructed. Elberton Granite is part of the Lexington-Oglesby Blue Granite Belt that extends southwest past Lexington, over an area 25 miles long and 15 miles wide. The granite has a blue-grey appearance and is predominantly made up of three minerals, white felspar, greyish quartz, and the black flecks of biotite. The Elberton granite formed from an igneous intrusion within the Georgia Inner Piedmont region of eastern Georgia during the Mississippian, ~320 million years ago.

4. The interior walls of the memorial are constructed of white Georgia marble that is also used in the Lincoln Memorial. Although there are several different "varieties" of marble within Georgia, they all seem to be variations of the same marble deposit, Murphy Marble. The Murphy Marble Belt runs from North Carolina down through Georgia and centers on Tate, Georgia, where the Georgia Marble Company mines the marble. It is the Georgia Mining Company that provided the marble for the Lincoln statue. The specific variety of marble for the Lincoln statue comes from the Cherokee White Quarry, which is mixed in among folded gneisses and schists within the Murphy Marble Belt. The Cherokee White Marble is a partly dolominitic but nearly pure calcite marble. These marbles have been extensively quarried since 1840. The Murphy Marble started off as a Lower Cambrian limestone that was eventually metamorphosed and folded numerous times during the lower Paleozoic from the Middle Ordovician through the Early Mississippian.

4. The floor is made of Tennessee Pink Marble. Also used in the Lincoln Memorial, the Tennessee Pink Marble is interesting in that it actually isn't a marble, it is a limestone, meaning it was never metamorphosed like the Yule Marble. The "marble" even includes such sedimentary structures as cross bedding, bryozoan fossils, crinoid fossils, and stylolites. The stone is part of the Holston Formation, which formed 460 million years ago during the Middle Ordovician, along the continental shelf of Laurentia (the northern continent). The Tennessee Pink Marble is found along the eastern part of Tennessee, near Knoxville.

The bronze statue of President Jefferson

6. The statue of Jefferson is composed of bronze and rests on a black Minnesota granite. Like the "Georgia Marble" listed above, there are no specific references for the "black Minnesota granite", especially considering that granite is very rarely, if ever, found "black". The best assumption I can make about which building stone was used for this (without seeing the rock in person) is that the pedestal is actually composed of a gabbro. Gabbro, like granite, is a course grained, intrusive, igneous rock, so in essence they will have a similar appearance. Unlike granite though, gabbro is composed of mostly dark colored minerals without any quartz, unlike granite which has mostly light colored minerals and is predominantly quartz (a light colored translucent mineral). Within the state of Minnesota, the main gabbro being quarried at the time of the construction is the Duluth Gabbro Complex. The Duluth Gabbro Complex began intruding into the Minnesota host rocks approximately a billion years ago during the Late Precambrian. The Complex is made up of several different rock types from repeated igneous intrusions over a ~200 million year time span. These rock types include anorthositic gabbro, normal gabbro, ferogranodiorite, and granophyre. The oldest rock of the complex is the anorthositic gabbro, which is made up of 75-90% the mineral labradorite, a black colored mineral, making this a very black rock indeed. It is my hypothesis that the Jefferson pedestal is composed of this anorthositic gabbro (until I am able to get more information).

7. The statue of Jefferson also has a gray Missouri marble ring surrounding the base. Similar to the Tennessee Pink Marble above, the Missouri Marble not really a marble, but a limestone. One of the ways that this can be identified is the presence of fossils and stylolites, both of which would have likely been destroyed if the rock were to be metamorphosed. Unfortunately the specific rock used in the Memorial is not identified and limestone is found all across the state of Missouri. However, the Missouri state capital building used limestone in its construction and it was noted that once the interior limestone was polished, it gained the distinction of being called "marble". Based on the time period of the Capital Building's construction (1915-1917) and this common misnomer of the rock, I feel that the same rock was used for the Jefferson Memorial. The Capital interior stone is known as "Napoleon Gray marble" and can be found not only in the state capital but also in the NY Stock Exchange and the Legion of Honor: The Fine Arts Museum in San Francisco. The Napoleon Gray is more commonly known as Phenix Limestone, from the nearby town of Phenix, or geologically it was called the Burlington and Keokuk limestones. These limestones (the Burlington and Keokuk) are difficult to differentiate and are typically grouped together as part of the Osagean Series. The Burlington and Keokuk limestones formed during the flooding of North America 325-360 million years ago during the Early Mississippian. This flooding produced a shallow inland sea, called the Kaskaskia Sea, which allowed for the deposition of many fossils including crinoids, brachiopods, corals, and bryozoans. 

View of the Memorial from across the Tidal Basin. From this angle you can see straight through the memorial.


Tuesday, March 05, 2019

Geological State Symbols Across America - District of Columbia

The next state up for the Geological State Symbols Across America is:

District of Columbia
AKA Washington D.C.

You can find any of the other states geological symbols on my website here: (being updated as I go along this year).

                                                                             Year Established
State Rock: Potomac Bluestone                                    2015
State Fossil: "Capitalsaurus"                                        1998