Seneca Thrust Fault EarthCache at Mulligan's View EarthCache

Mulligan’s View exposure
About 1 mile (1.6 km) west of Camp Greenville along YMCA CAMP Road (a.k.a. Solomon Jones Road), a cut at Mulligan’s View exposes an edge of a Six Mile sheet klippe near the top of the Front (see below). This cut is approximately 150 feet long and provides a northwest view of the geologic relationships. A second exposure, a small borrow pit located immediately to the west along Solomon Jones Road, shows the same rock units and similar structural relationships.
BONUS: continue a short distance down the road to PRETTY PLACE. If it is open, it's a fabulous overlook & very much worth seeing since you are already up here. Visitors can usually come from sunrise to sunset at No Charge (except during private events).

Please exercise caution when visiting the site. Stay off the road and be mindful of traffic. The exposed rock face is accessible from the pull off along the roadside, but climbing on the rocks is NOT recommended.

This is an Earthcache! An Earthcache is a special type of geocache where there is no container to find - instead you are looking at unique geological features of the area and need to answer questions and/or posting a photo to your log in order to claim the find.

       IN ORDER TO COMPLETE YOUR FIND OF THIS EARTHCACHE: PLEASE VISIT THE SITE AND DO AT LEAST ONE OF THE FOLLOWING QUESTIONS/TASKS BASED ON YOUR OBSERVATIONS:
       Send the answers to me in a message or email through geocaching.com (OR POST a PHOTO TO YOU LOG IF DOING THE PHOTO OPTION) The SAME DAY YOU LOG YOUR FIND is preferable:

Questions for Cachers To log this EarthCache,.
1. Describe the rock layers visible at the road cut. What evidence suggests that the older rocks were thrust over younger ones? ________.
2. Identify any slickensides or deformation features at the site. What do these features reveal about the movement along the fault? ________.
3. Examine the erosional patterns visible at the road cut and the surrounding landscape. How might erosion have contributed to isolating the Six Mile sheet klippe? ________.
4. Why are thrust faults such as the Seneca Thrust Fault significant in understanding the geological history of the Appalachian Mountains? ________.
5. Post a photo to your log of the area near the coordinates (including yourself or your group if you prefer). Posting this photo in your log will qualify as one of your answers/tasks.

****NOW FOR THE EARTHCACHE****

The Seneca Thrust Fault at Mulligan’s View Introduction:

Just what is a Thrust Fault? A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust faults occur when one section of land slips over another at a low angle when the land is compressed.

To the north-northeast of Caesars Head, small Six Mile sheet klippe (a klippe is a geological feature of thrust fault terrains, the remnant portion of a nappe (a nappe is a large sheetlike body of rock that has been moved far from its original position) after erosion has removed connecting portions of the nappe) crop out at the top of the Blue Ridge Front (a "front" in the context of the Six Mile sheet klippe in upstate South Carolina refers to the leading edge or boundary of a thrust fault system, where older rocks have been transported over younger rocks due to compressional tectonic forces) along Solomon Jones Road leading to Camp Greenville. Along this road, parts of these klippen and the Seneca fault are exposed in roadcuts and borrow pits at approximately the same elevation. These exposures allow detailed observations of deformation that has overprinted the Seneca fault.

Poor Mulligan’s View is located approximately 1 mile west of Camp Greenville along Solomon Jones Road (YMCA Camp Road). It offers a unique glimpse into the geological forces that shaped the Appalachian Mountains. At this road cut, visitors can observe an exposed section of the Six Mile sheet klippe, a remnant of a large nappe associated with the Seneca Thrust Fault system. This site highlights the complex processes of thrust faulting and erosion that have influenced the region’s geology over millions of years.

Two rock units are exposed at Mulligan’s View: Six Mile sheet Poor Mountain Formation (PMF) and Walhalla sheet Table Rock Plutonic Suite (TRS) gneiss (gneiss is a metamorphic rock with banded texture and poorly developed cleavage (in geology, cleavage refers to a type of rock feature that develops due to deformation and metamorphism, typically in fine-grained rocks. It is a form of secondary foliation (repetitive layering) characterized by the alignment of minerals in a preferred orientation, formed by high-temperature and high-pressure processes). Poor Mountain rocks are dominantly fine- to medium-grained, well layered and well foliated amphibolite (a coarse-grained metamorphic rock that is composed mainly of green, brown, or black amphibole minerals) and feldspar (Feldspar is the name of a large group of rock-forming silicate minerals that make up over 50% of Earth's crust), with minor interlayered schist (a foliated metamorphic rock made up of plate-shaped mineral grains that are large enough to see with an unaided eye). Soft, saprolitic (a type of soil or rock that has undergone significant chemical weathering, resulting in a soft, decomposed material that retains the structure of the original rock), gray Table Rock Plutonic Suite biotite quartzo-feldspathic gneiss (TRS gneiss) is leucocratic (having a light color), fine-crystalline, and well foliated. TRS gneiss also contains several contorted, discontinuous, irregular masses and layers of schist. Small bodies of pegmatite are adjacent (pegmatite is an igneous rock ((igneous rock is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava)) characterized by its very coarse texture and large interlocking crystals, typically larger than 1 cm, and sometimes exceeding 1 meter. It is primarily composed of minerals like quartz, feldspar, and mica, similar to granite).

Look closer at the black, thinly layered rock that is Poor Mountain Amphibolite. See if you can see the black layers. You might can see long, shiny, blade-shaped crystals all pointing in the same direction within each black layer. These crystals are a mineral called hornblende. Because all of the hornblende crystals in the dark layers point in the same direction, the rock flakes apart into thin layers, between the dark layers, gray quartz, white plagioclase feldspar, and a mineral called epidote form thin, ligh- colored layers. This amphibolite also contains a great deal of iron. The rust-colored stains on the wall are caused by iron weathering out of the amphibolite.

Folds are recognized in the exposure. These folds are well defined by foliation in the TRS gneiss and schist layers and by the sharp contacts between PMF amphibolite and TRS gneiss.
     Two conspicuous amphibolite bodies are visible in the exposure. The dark amphibolite is approximately 4 ft wide and runs diagonally up across the center of the cut.
     The rock units in the exposures are partly altered and soft as a result of intense weathering generally developed near the top of the Blue Ridge escarpment (~3000 ft. elevation). Structural relationships are more discernible after thunderstorms have washed down the exposure.
      A layer of schist along the fault surface represents a mechanically weak zone through which thrusts have splayed upward from the Seneca fault.

Exceptional rock exposures occur in the Carolinas along the balds of the Blue Ridge Front (~3000 ft. elevation). These exposures are the result of a complex interplay between Cenozoic tectonic activity and erosion. The Seneca Thrust Fault is located in the vicinity of Camp Greenville, South Carolina.

Geological Background: The Seneca Thrust Fault is a major geological feature formed during the Alleghanian Orogeny, a mountain-building event that occurred approximately 300 million years ago when the ancient supercontinents of Gondwana and Laurentia collided. This collision caused immense compressional forces, leading to the formation of thrust faults. Thrust faults are characterized by older rock layers being pushed over younger ones due to horizontal compression.

The Six Mile sheet klippe at Mulligan’s View is part of a nappe, a massive sheet-like body of rock displaced far from its original position. Erosion has since removed much of the connecting portions of the nappe, leaving isolated remnants called klippen. This exposure reveals key details about the structure and movement of the Seneca Thrust Fault.

Features of Interest at Mulligan’s View:
Klippe Exposure: The road cut exposes the edge of the Six Mile sheet klippe, allowing visitors to observe how this portion of the nappe was displaced and preserved.

1. Rock Relationships: The fault zone displays older metamorphic rocks atop younger sedimentary layers, a hallmark of thrust faulting.
2. Fault Plane Evidence: Look for slickensides (polished surfaces caused by fault movement) and deformation features such as folds and fractures within the exposed rocks.
3. Erosional Remnants: The surrounding landscape, shaped by millions of years of weathering and erosion, provides a northwest view of the geological relationships between the klippe and the underlying formations.

What to Observe at Mulligan’s View: When standing at the road cut, cachers can observe the following features that illustrate the geology of the Seneca Thrust Fault:

• Rock Color and Texture: Notice the distinct layers of rock exposed in the cut. The predominant rock at the site is a whitish metamorphic rock with a coarse-grained texture. This rock contrasts with darker, finer-grained layers that may appear below or interspersed, indicating differences in rock composition and age. The lighter color often reflects the metamorphic origins and high quartz content of these rocks.
• Wavy and Layered Patterns: Notice the undulating or wavy appearance of some layers, a result of folding under immense compressional forces. These folds may appear as gentle curves or sharp bends in the rock layers, showcasing deformation during thrust faulting.
• Deformation Features: Look closely for evidence of folding or faulting within the exposed layers. Folds may appear as curved or wavy lines in the rock, while fault planes may show abrupt changes in the orientation of the layers.
• Slickensides: Examine closely the surface of the rocks for smooth, polished areas on the white rock. These slickensides often have linear striations, which indicate past movement along the fault, evidence of the directional movement along the fault plane.
• Layer Contacts and Boundaries: Observe the clear boundaries between different types of rock where one type of rock transitions to another.. The contact between the coarse, whitish metamorphic rock and darker, sedimentary-looking rock provides key visual evidence of the thrust fault, where older rocks being thrust over younger ones.
• Erosion Effects: Examine how weathering has shaped the rock face. Softer layers may have eroded more, creating subtle recesses or grooves, while harder layers form protruding ridges. These patterns reflect the varying resistance of the rocks to weathering processes.

Conclusion: The road cut at Mulligan’s View offers an accessible and educational opportunity to explore the geological history of the Appalachian region. Through careful observation, EarthCachers can gain a deeper appreciation for the processes of thrust faulting, erosion, and landscape evolution.

FTF Honors Go To . . . RobinMohawk!!!