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Geology Sign
Introduction
The oldest part of the park is found in the ancient sandy soil beneath your feet. The terraced landscape, or stair-step formations, found in this part of Virginia formed as sea-level rose and fell in response to changes in continental glaciers and uplift. The Shirley formation, named for the Shirley Plantation, is found in the area of Cypress Creek and north of the Pagan River. Each land area is geologically named based on its soil and rock strata. In this case, riverbank and sand deposits combined to create the loamy soil, a soil with roughly equal proportions of sand, silt, and clay. Found below the Shirley Formation is the older Yorktown Formation which contains fine marine sand and fossils. One of those marine fossils is the Chesapecten, a large species of scallop found in the shallow seas along the Mid-Atlantic. Though other scallops lived during these times, the Chesapectens were the most abundant. The jeffersonius lived during Early Pliocene time, found in the Yorktown Formation. The madisonius lived during Late Pliocene time, found in the Shirley Formation. The Chesapecten Jeffersonius became the official fossil of the Commonwealth of Virginia in 1993.
Some Facts to Consider
- Geologists have recorded five transgressive-regressive cycles to the Coastal Plain marine environment during the Pliocene (5.3 to 2.6 million years ago) and late Pleistocene (2.5 million years ago to 11,700 years ago).
- Though all the subsoil sediments found in the park are loamy, there are five different versions of loamy subsoil. Rumford (sandy loam) and Uchee (sandy clay loam) cover most of the park area between the creeks.
- The Chesapecten Jeffersonius was in such abundance during its time that it is used as an index fossil by geologists because it is easily identified by the 9 to 12 ribs of the shell spreading out 7 to 11 inches and the rounded edge of the shell.
- Loam is the kind of soil which is neither sand nor clay. As it approaches in nature to sand, it is called “sandy loam” or “light loam”. What do you think loamy soil looks like?
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Full Question: Loam is the kind of soil which is neither sand nor clay. As it approaches in nature to sand, it is called “sandy loam” or “light loam”. As it approaches in nature to clay, it is called “clayey loam” or “heavy loam”. What do you think loamy soil looks like?
Answer: Loamy soil is dark brown in color, not red or gray like clay, and not light brown like sand or silt.
- In some areas of the park you may find greenish-blue clay. What do you think caused this particular coloring of this fine, marine sediment?
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Clays with this greenish-blue color are called 'gleyed' and are found in areas that have been saturated with water at some point in time. If there is a reddish tint to the clay, there was iron present. This connects the soils to its history of being a seafloor once upon a time.
- The loamy soil of the park contains the three basic soil particles, silt, clay and sand, in about equal amounts. Why does this make it the ideal garden soil?
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Because there are three different soil particles, there are three different particle sizes allowing larger pores spaces for water, nutrients, and air in the soil for plants to use. In some types of loam, 40-60 % of the soil volume is made from the pores spaces.
- The large Chesapecten Jeffersonius shells were first discovered in north america. You might guess that this particular fossil was named for Thomas Jefferson. Do you know why it was named so?
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It was named for Mr. Jefferson because of his interest in natural history. It also celebrates the Chesapeake Bay, the largest estuary in the world.
- The vast amount of oysters along the riverbed and banks were a nuisance to wooden ships of the settlers, but also vital to settlements in this area. Why is that?
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Full Question: European settlers found mounds of mollusk shells discarded by the Native Americans when they arrived. The large Chesapecten shells were used as bowls and scraping tools. The vast amount of oysters along the riverbed and banks were a nuisance to wooden ships of the settlers, but also vital to settlements in this area. Why is that?
Answer: The oysters were so plentiful in the area that they were a food source for the earliest settlers and may have made it possible for the settlers to survive and flourish here.
- A good index fossil is one with four characteristics. What are those characteristics?
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Full Question: The word fossil has a Latin origin, from fossilis, meaning “dug up” and that remains the key attribute of what we label as fossils. Every fossil tells us something about the age of the rock it’s found in. Index fossil tells us the most, because they are used to define periods of geologic time. A good index fossil is one with four characteristics. What are those characteristics?
Answer: It is distinctive, widespread, abundant and limited in geologic time. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms.
- Out of all the many rivers found in Virginia, what makes the James River stand out among the others?
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Full Question: Windsor Castle Park looks out onto the Pagan River that feeds into the James River. The James begins where the Jackson and Cowpasture rivers join in northern Botetourt County and flows 347 miles to reach the Chesapeake Bay. Out of all the many rivers found in Virginia, what makes the James River stand out AMONG the others?
Answer: Often called America's Founding River because of the early settlers, the James River is the largest and longest river in Virginia. A third of all Virginians depend on the river is some way.
- there are several rises and falls as you travel along the trails on the edges of Little Creek and Cypress Creeks. What created the various elevation changes?
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Full Question: Though the elevation of the Park is less than 50 ft throughout, there are several rises and falls as you travel along the trails on the edges of Little Creek and Cypress Creeks. What created the various elevation changes?
Answer: Over the ancient history of the Park, sea level, as well as river and creek levels, have ebbed and flowed, eroding the surface of the landscape.
- The Pagan River was used to export what crop, prior to it shifting to Suffolk before 1921?
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Full Question: The Pagan River is a 12.5-mile-long tributary of the James River that allowed Smithfield to become a thriving trading post for early settlers. The river's name is thought to be from the Algonquin word for “pecan” as pecan trees were plentiful along the banks. The Pagan River was used to export what crop, prior to it shifting to Suffolk before 1921?
Answer: The banks of the Pagan River in Smithfield were once lined with peanut warehouses and peanuts were the cash crop of the town until a devastating fire in 1921. It wasn't until the late 1930s that Smithfield Foods started changing the economics of Smithfield.
- About how much time would you have to wait to witness a low tide followed by a high?
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Full Question: At certain times of the day, the tidal marshes of Little Creek and Cypress Creek drain, revealing the mudflats and fiddler crabs. A few hours later, water flows back into the creeks from the Pagan River, covering it all. This continues each day with water ebbing and flowing from the Pagan River. About how much time would you have to wait to witness a low tide followed by a high?
Answer: Coastal Virginia experiences two high and two low tides each day, each one about 6 hours and 25 minutes apart. As the tide flows into the James from the Chesapeake Bay, it enters the Pagan River and then into Little Creek and Cypress Creek.