Arkansas provides many great opportunities to explore the great outdoors. This earthcache takes you on a special hidden treat that is located at a historical landmark. While in the "Natural State" you will not want to forget your camera, a walking stick, and a buddy or two to go out and enjoy nature.
In this Earth Cache lesson you'll lean about a fieldstone in Arkansas.
After completing this Earth Cache you will have a better understanding of:
- What exactly is fieldstone
- Where it comes from in Arkansas
- Geological Time Periods
- Divisional Regions of Arkansas
- Plateau Regions of Arkansas
- Elevations
- Arkansas Quarries
- Uses of Fieldstone
A bit about Ground Zero
Ground zero is a historic site at the junction of Oakmont and Cunningham Drives in Bella Vista, Arkansas. It is a circular masonry structure, faced in rough-cut fieldstone, and capped with a concrete lid whose design is intended to allow rainwater to enter while minimizing the introduction of debris. Built around 1927, it is significant as the only known structure of its type in Benton County, and for its association with the early development of Bella Vista.
What exactly is Fieldstone?
Well, Fieldstone is exactly as the word means, Stones found on the top soil in fields and surrounding areas. There are several theories of where the stones came from, in my opinion I believe from study that it came from two possible sources: 1) the edge of a great glacier that covered much the North America and 2) massive tectonic upheaval in which the region was all underwater. But lets get a bit more in-depth with the meaning.
Dimension stone is defined as rock that is removed from its original site to be used with minor alteration (rough stone) and rock that is broken, sawn, and/or ground and polished (cut or dressed stone) for use as building and/or ornamental stone. While most of the high-quality dimension stone produced in Arkansas is used in state, some is shipped to markets worldwide. Limestone and sandstone are used as dimension stone in Arkansas. Historically, much nepheline syenite was used as hand-worked building stone in the late nineteenth and early twentieth centuries in the Little Rock (Pulaski County) area, but beginning in the middle 1940s, those labor-intensive activities gave way to the use of crushed stone for syenite. A small market exists, also, for the use of white massive vein quartz for decorative stone in fireplace mantles and other small interior projects. The mining of dimension stone is labor intensive, and the cost of the product delivered to an end user is tied to both labor and transportation costs.
Rough Stone
Rough stone may be subdivided into field stone and rounded river stone. Field stone typically is simply picked up from loose debris material present on hillsides. It may or may not be covered with moss and typically has minor rounding due to weathering and mass transport down slopes. Sandstone is the dominant rock type of field stone since it often is deposited as thin flaggy beds, although some weathered limestone is also recovered for decorative use.
Flagstone is a variety of field stone that consists of relatively thin plates, relative to its width and breadth. Rounded river rock is typically present on gravel bars of major drainages. This rock is near equi-dimensional in form and well rounded. It is hand picked and sorted based on size. Sandstone is the most commonly utilized stone. Several of the companies involved in dressed stone production in Arkansas also produce field stone as an additional product. One company, Beauty of Stone of Crawford County, produces rounded river stone as a major product. This stone has been shipped to custom building stone markets in the eastern United States.
Field stone and rounded river stone are used in a variety of exterior building applications, including walls, walkways, decorative fountains, and patios, as well as decorative applications such as garden rock and artificial waterway fill. In Arkansas, rough stone is produced from areas dominated by sandstone within the Ozark Mountains, Arkansas Valley, and Ouachita Mountains regions.
So as I mentioned There are several theories of where the stones came from, in my opinion I believe from study that it came from two possible sources: 1) the edge of a great glacier that covered much the North America and 2) massive tectonic upheaval in which the region was all underwater. Let's look into the birth of said fieldstone
A frozen wastelands depository
The Laurentide Ice Sheet was a massive sheet of ice that covered millions of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs. It last covered most of northern North America between c. 95,000 and c. 20,000 years before the present day. At times, its southern margin included the modern sites of New York City and Chicago, and then followed quite precisely the present course of the Missouri River up to the northern slopes of the Cypress Hills, beyond which it merged with the Cordilleran Ice Sheet. The ice coverage extended approximately as far south as 38 degrees latitude in the mid-continent. It is true that most Field Stones did come from Glaciers back in the Ice Age. As the heavy 2 mile thick sheet of ice would carve through the land it would push massive amounts of rock, just like water does with sediment in a stream. As the glaciers melted away these stone of many shapes and sizes would be one of the tall tell clues a glacier was present....but.....no glaciers reached as far south as Arkansas. The ancestral Mississippi and Ohio rivers delivered tremendous amounts of glacial outwash deposits to the eastern part of Arkansas along the river's pathways. Minor alpine snow packs occurred in the Ouachita Mountains, and terrace deposits developed along the major rivers. The northern highlands are greatly eroded, and Crowley's ridge had the Mississippi River flowing on its west side and the Ohio River on its east side, meandering in the eastern part of the state.
Seas of Change
Geological studies done in Newton County have shown that this area was dominated by ancient seas, prehistoric upheavals, and past climates. The rocks were formed from sediment deposited on the bottom and along the shoreline of ancient oceans. The structure is the result of geologic forces that uplifted the region out of the ocean hundreds of millions of years ago. More recent weathering and erosion of these rocks sculpted the shape and form of the present surface. The oldest rocks are Ordovician age (505 to 438 million years ago). They are found in the bluffs, streambeds and flood plains of the major streams in the northern part of the county. These rocks represent lagoons, barrier islands, beaches and shallow ocean environments. 
The Mississippian Period (360 to 320 million years ago) saw a landscape that was filled with a rich dry-land ecosystem of plants and animals. These rocks represent continental shelf and near shore marine environments. Rocks of the Pennsylvanian Period (320 to 286 million years ago) cap the mountains of the county. They are the result of sediments deposited by ancient deltas and river systems along the margin of a sea. After that, for several million years, a continental fragment collided with the ancestral North America. This collision pushed up the Ouachita Mountains to the south and warped the Ozarks out of the ocean for the last time.
Lets Talk about the past!
Geologists have a warped sense of time. Maybe not as bad as astronomers do, but it is still mind-boggling to think in millions and billions of years. As best that scientists can figure, the first rocks formed on the earth about 4.5 billion years ago. The earth is maybe 6 billion years old, but took it took a while for the crust to cool off and solidify. The rocks of the earth are the key in determining not only how the world is put together, but how old it is. You've seen places on the side of the road where the rocks lay in horizontal beds on top of each other. These are sedimentary rocks. In those parts of the world where the layers haven't been jumbled together by mountain-building forces, the bottom layers are older. Like a detective, scientists read the clues and can tell the ages of the rocks by the fossils in the layers. Since the 1950's, special techniques have been devised by geologists using radioactive isotopes present in rocks to accurately age date sedimentary, igneous, and metamorphic rocks. Guess what! The age dates correlate well with that of the fossil record found in sedimentary rocks, adding support to the acceptance of the Geologic Time Scale. So, by looking at road cuts, quarries and sections of rock cored by drilling, geologists pieced together a history of the planet.
A scale of time left by the rocks
At the side of this page as you scroll down is the time scale of geologic history. The numbers on the left-hand side of the table are millions of years before present time, and in each section of the table, the scale changes. That change means recent events recorded in the rocks are much better known than the older happenings of our earth, and the events of the very early world are mostly unknown. There are no fossils in the oldest rocks because there were no living things. In this geologic column, it is younger on the top than on the bottom, just like the piles of paper on my desk, or a layered sequence of sedimentary rock.
Four major divisions
Roughly, we can divide the time column into units comprehensible to us by saying the Cenozoic was the past time from present day back to the disappearance of the dinosaurs. The Mesozoic was the time that dinosaurs lived, the Paleozoic was before the dinosaurs with fossil plants and sea animals, and the Precambrian is the oldest group of rock: mysterious because so little is known about it. And get a load of this: Precambrian time occupies eighty percent of the earth's history!
On the previous page, we told you some of the active processes that assist the continents in their slow-motion dance around on the planet's surface, bumping and banging together (called plate tectonics), creating mountains when they collide. Volcanoes and erosion are also active forces that shape the land. Volcanoes bring up new material for land, erosion wears it down. That's part of the rock cycle.
A trip through time
Here is a map showing the regions of Arkansas today. The timeline summary below tells you how our part of the world got like this.
Get your brain into major time-lapse mode, and try to follow the events summarized in this geologic history of Arkansas as we go backwards into time:
Summary of geologic history in Arkansas
Cenozoic Era
Quaternary present back to 1.6 million years before present (MYBP)
Holocene: The early indians lived here in a drier climate than we have now. Wind blown dust and sand dunes, along with stream deposits covered portions of the land, but erosion was also active, and carried away surface material. The Ozark highlands of north Arkansas looked similar to the canyon lands of the western United States today.
Pleistocene: This was the time of the glaciers, but no glaciers reached as far south as Arkansas. The ancestral Mississippi and Ohio rivers delivered *tremendous* amounts of glacial outwash deposits to the eastern part of Arkansas along the river's pathways. Minor alpine snow packs occurred in the Ouachita Mountains, and terrace deposits developed along the major rivers. The northern highlands are greatly eroded, and Crowley's ridge had the Mississippi River flowing on its west side and the Ohio River on its east side, meandering in the eastern part of the state.
Now remember, we're going backward in time ----
Tertiary (1.6-66 MYBP)
Neogene: Erosion happened. No known deposits occurred.
Paleogene
Oligocene: Erosion. No known deposits occurred.
Eocene: There was a very shallow sea receding from the northeastern half of the state called the Mississippi Embayment, as river and ocean deposits filled it in. The highlands of the Ozark Mountains have been eroding away for millions of years, and bauxite, lignite, clay, sand and silt were deposited.
Paleocene: The shallow sea covering southern and eastern Arkansas had limestone reefs near the shoreline, capped by dark marine shale. Bauxite developed on Cretaceous alkalic intrusions (magma that came up from deep in the earth). The highlands were eroding.
The boundary with this unit and the next older one marks the time of the end of the dinosaurs, mass extinction caused possibly when an asteroid collided with the earth, perhaps off the Yucatan peninsula...
Mesozoic Era
Cretaceous (66-144 MYBP)
Late Cretaceous Shallow water sands, marls, and chalks were deposited in the Mississippi Embayment, along with water-lain volcanics in the lowest unit in this sequence.
Mid-Cretaceous (about 100 MYBP) The downwarping of the earth's crust that formed the Mississippi Embayment allowed shallow seas to invade the middle part of North America as far north as Cairo, Illinois. Alkalic igneous activity began to occur in central and southwest Arkansas, which is now exposed as the areas of Magnet Cove, Potash Sulfur Springs, Granite Mountain, and the diamondiferous pipe at Crater of Diamonds State Park.
Early Cretaceous Dinosaurs were on the land, and the Arkansaurus lived near the coastline of the old Gulf of Mexico in southern Arkansas. Near shore deposits of clay, sand, gravel and limestone were laid down. Very salty lakes or lagoons south of the Ouachita Mountain area resulted in deposition of gypsum and anhydrite.
Jurassic (144 - 208 MYBP)
Aside from the dinosaurs made famous by the movie of this period, erosion of the highlands was continuing in north Arkansas, and sediments from this time are not exposed at the surface in the state. In south Arkansas, deposition of terrestrial redbeds, shallow water shales and limestones occurred, with major salt intervals in the lower sections.
Triassic (208 - 245 MYBP)
The earliest dinosaurs appeared. Sediments are not exposed in Arkansas. Andesitic volcanic action in the extreme southwest corner of the state. The highlands were eroding.
Paleozoic Era
Permian (245 - 286 MYBP)
Sediments not exposed. Erosion of highland.
Pennsylvanian (286 - 320 MYBP)
Ouachitas - This is the time of South America, the Caribbean Plate, or another land mass bumping into us, causing the Ouachita Mountains to form. Some of the sediments were squeezed like toothpaste into mountains, while major thrust faults and reverse fault lines formed in the brittle units. The ocean over the area was getting more shallow. Rapid deep water clastic (rock fragment) sedimentation happened.
Arkansas Valley - There was rapid infilling with clastic sediments along the ocean basin growth faults.
Ozarks - The ocean that covered this area had shallow-water clastic sedimentation. Fault lines formed in a NE - SW direction, diagonally across the area.
Mississippian (320 - 360 MYBP)
Ouachitas - The ocean was deep early in this period. The slow rates of deposition in the Ouachita trough came to an end with the last beds of novaculite. Sedimentation became very rapid and the ocean started filling in.
Ozarks - Deposition and partial erosion of shallow water limestones, shales and sandstones.
Devonian (360 - 408 MYBP)
Ouachitas - 48 million years of slow deposition of deep water novaculite and shale in the ocean.
Ozarks - Slow deposition and erosion of thin units of shallow-water clastics and carbonates.
Silurian (408 - 438 MYBP)
Ouachitas - 30 million years of slow deposition of clastic sediment in the deep ocean.
Ozarks - Deposition and partial erosion of thin shallow-water carbonates.
Ordovician (438 - 505 MYBP)
Ouachitas - 67 million years of deposition of alternating sandstone and shale in the deep ocean.
Ozarks - Shallow seas covered the area, with deposition of layers of carbonates with minor clastics.
Cambrian (505 - 570 MYBP)
Ouachitas - The oldest formation that is exposed is the Collier Shale, and geologists don't know how thick it is.
Ozarks - Cambrian rocks are not exposed in north Arkansas. Where clastic and carbonate sediments were deposited form shallow seats on top of the Precambrian igneous basement.
Precambrian
Events in the Precambrian are essentially unknown to us because it was SO LONG AGO and in Arkansas these rocks are not exposed. From sparse well data in the Ozarks, Arkansas Valley, and portions of the northern Mississippi Embayment, the Paleozoic rock layers are underlain by areas of rhyolite, metarhyolite, granite, and microgranite. These kinds of rocks are igneous, meaning they were once molten. Lower Paleozoic rocks in the Ouachitas contain Late Precambrian indicators, so geologists know that the Precambrian rocks are underneath the mountains and all of the other rocks in Arkansas.
Back to the Future
Now that we have a good understanding of where much of our rocks and minerals came from lets take a closer look at where we are today.
The geology of the Ozark Plateau Region is characterized by slightly southward-dipping sedimentary rock deposited mostly by shallow marine seas from the Ordovician through the Pennsylvanian Period. Caves and sinkholes are common in limestones of the Springfield Plateau with less karst development in the dolostone in the Salem Plateau. The Boston Mt. Plateau surface contains mostly sandstones and shales deposited by south/southwestward flowing streams during times of low sea level.
Today we can see the plateaus and the divisions from such sudden upheaval
-
-
The Salem Plateau contains the oldest rock at the surface - Ordovician dolostone, sandstones and limestones. This is also the lowest plateau surface with some of the highest elevations reaching between 800 and 1400 feet above sea level.
-
The Springfield Plateau contains mostly Mississippian age limestone and chert from the Boone Formation at the surface. This plateau is intermediate in elevation with some of its highest elevations reaching 1800 feet above sea level. The plateau surface consists mostly of gently rolling hills or an undulating topography, however in some places the Boone Formation forms steep hillsides separated by ravine-like drainages.
-
The Boston Mts. Plateau contains the youngest rock at the surface - Early Pennsylvanian sandstones and shales with minor limestones. This is also the highest plateau surface with some of the highest elevations reaching 2200-2500 feet above sea level.
Now I am sure you are wondering how I am tying all this in to fieldstone, but stick with me we are almost done.
Now you may have Recalled that I stated Field stone and rounded river stone are found in the Ozark Mountains, Arkansas Valley, and Ouachita Mountains regions.
Well, today in this era there are six natural geological divisions in Arkansas: the Ozark Mountains (a.k.a. the Ozark Plateau or Plateaus), the Ouachita Mountains, the Arkansas River Valley, the Coastal Plain, the Mississippi Alluvial Plain (a.k.a. the Arkansas Delta), and Crowley’s Ridge.
So while you are looking at ground zero and enjoying the beautiful historical landmark, think of the millions of years it took to create it. If you would like to read more about the specific Arkansas quarries this fieldstone may originated from I encourage you to look at the related web link.
Did you Know?
Settled agriculture requires relatively fine and uniform soils for intensive use, and large rocks pose additional risks for agricultural machinery, which they can damage if not removed. Because the stones are widely disseminated, removing fieldstone is a widespread and costly activity in early agricultural settlement. To prepare fields for cultivation, farmers would need to remove these stones, which requires significant manual labor. Until the 19th century, fieldstone was removed exclusively by hand, often with whole families participating in this task. Depending on the harshness of winters, this task would need to be repeated whenever frost levels would churn new stones into soil surfaces. Thus, land with many field stones was and is considered marginal and is assessed for tax purposes well below land that is considered stone-free.
In mechanized agriculture, stone is usually removed by a tractor attachment called a rock picker. A chain-driven wheel rotates a graded scoop picking surface rocks from the soil and shakes off excess soil. A hydraulic lift then tilts and empties the rock bucket, usually along the perimeter of the farm. Washed and split, field rock is considered an attractive landscape and building material, and can be expensive at building supply stores.
Requirements: (please do not put your answers in the log)
Now that we learned about the origins of field stone, take a moment to study ground zero. With the information above, and information at GZ you should be able to answer the following questions. You have 24 hours to send me an email (found in my geocaching profile) with the correct answers. Failure to do so will result in the removal of your "Found it log". Please add the GC code and title in the subject line. If you are sending answers for multiple people in your group, please add all the names in your email to ensure they don't have their log deleted :) Photos with you/group of the area would be greatly appreciated.
1: What is Field stone?
2: What are the some causes of large rock such Fieldstone being deposited?
3: Was there Glacier in Arkansas?
4: During what age was the cause of most of Arkansas tectonic changes?
5: Name the six physiologic divisions in Arkansas
6: What Divisional region is Ground Zero located at?
7: Name the three plauteaus of Arkansas.
8: What Plateaus is Ground Zero located on?
9: What is the general elevation of ground zeros plateau?
10: What is the structure at Ground Zero?
11: How tall is the fieldstone wall at the structure?
13: What was this inteded use of this structure (original use)?
14: What is to roof of the structure made of?
15: Define Situ and explain why it's a good description of Ground Zero.