Congrats to fizacist on FTF!! He has written a nice blog entry about geocaching along Curry Brook.
There are two ways you can get to this earthcache. Both involve considerable walking over rough, wet and slippery terrain. The two parking coordinates will allow you to approach GC8YR66 which is downstream from the earthcache or GC8D8JV which is upstream from the earthcache. The "downstream" coordinates are the end of a road. There may be a schoolbus parked in the dead end, so I'd recommend parking back a bit from that. From those coordinates follow the stream bed down to Curry Brook. Believe it or not, the stream bed was once a road! If you're coming from the "upstream" parking area, follow the trail in to "Into the Abyss" geocache and go downstream from there.
Curry Brook is found in the community of West Brooklyn,southwest of Avonport. The brook runs south to north off the mountain in a meandering way and empties into the Gaspereau River on its way to the Minas Basin. There are several smaller falls along this tributary, ranging between five to ten feet in height, which are very picturesque. The falls pictured below are farther upstream, near GC8D8JV (FF2019: Into the Abyss). There are several geocaches along the stream and there is a trail to GC8D8JV from the road.
The terrain rating is high and should be done with caution. It is wet under foot and could be slippery but an awesome area to see with all sorts of geology. Watch for fossils in the area as supposed to be present in the Deveonian Horton era. We suggest using the parking coordinates and walking the steam bed, which is easier when the water is low. Even better would be to have a car at both ends and walk down the steam and rubber boots would be a plus.
Geological History of Curry Brook
The pre-Carboniferous geology of Nova Scotia is best considered in terms of two broad tracts, one to the north and one to the south of the Cobequid-Chedabucto Fault Zone (CCFZ). These two tracts developed independently prior to their juxtaposition during the midDevonian Acadian Orogeny (ca. 410-380 Ma). This area would be south of the Cobequid chedabucto Fault Zone.
Curry Brook is located in the geological area of the Horton group which is part of the Devonian age. The Devonian Period occurred from 416 million to 358 million years ago. This age is composed of thick sequences of grey to dark grey clay shale alternating thin bedded grey shale and siltstone. Fine sandstone and green mudstone and or slit stone often associated with thin dolostone and limestone in thin beds or kunkur nodules. The fine grained rocks are often fissile, pyritic contain septarian nodules, fish debris and ostracods.
The Stone along Curry Brook
Slate is a fine-grained, foliated metamorphic rock. The tectonic environment for producing slate is usually a former sedimentary basin that becomes involved in a convergent plate boundary. Shales and mudstones in that basin are compressed by horizontal forces with minor heating. These forces and heat modify the clay minerals in the shale and mudstone. Foliation (layering) develops at right angles to the compressive forces of the convergent plate boundary to yield a vertical foliation that usually crosses the bedding planes that existed in the shale.
Siltstone is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Siltstone generally are red and gray color with flat bedding planes. Darker colored siltstone have plant fossils and other carbon-rich matter. It is hard and durable and does not easily split into thin particles or layers. Siltstone is deposited in a similar environment with shale, but is usually located near the old delta, lake or sea shore, where calm currents cause less particle suspension.
Curry Brook Fault
The slate along the brook has been pushed up by a fault. There are two fault lines seen on the map. Gaspereau Valley Fault and Blue Beach Fault.
An enlarged portion of the map is shown below, with Curry Brook circled.
What Are Faults?
The surface of Earth is like a giant puzzle, and all the pieces that make up this puzzle are called tectonic plates. Although these giant rock puzzle pieces fit together very nicely, they don't stay in place because they are floating on the layer below us, the mantle. This layer is like the consistency of silly putty - sort of like a liquid and yet sort of solid, too.
The plates float around on the mantle like ice floats on a pond. The movement of the plates is incredibly slow, but since the plates are so big, when they bump into and rub against each other, we get massive events like volcanoes and earthquakes. And along these plate boundaries, we find faults. Faults are cracks in the earth's crust where movement occurs on at least one side. So, in order for a crack in the ground to be a fault, one side or the other has to move, but sometimes both sides move, too!
What Causes Faults?
Faults are classified by how they move, and there are three main types of stress that cause movement along faults. The stress occurs because, as mentioned before, the plates fit together really well, but also float around on the mantle and rub against each other.
Tensional stress is when slabs of rock are pulled apart. Imagine stretching a rope out all the way and then continuing to pull on it from both ends. You're putting tension on the rope because it's being pulled in opposite directions. The same is true for tensional stress in rocks.
Compressional stress is when slabs of rock are pushed together. They are literally being compressed into one another. This is like when two cars crash into each other - they're compressed into smaller, crumpled versions of what they were before.
Shear stress is when slabs of rock slide past each other horizontally in opposite directions. The rocks are not smashed into each other or pulled apart, but their edges slide along each other with a lot of friction. This is like when the side of a moving boat slides along a dock before coming to rest or your rub your hands to warm them up.
To log this Earthcache visit the viewing location. Please answer the following questions and send in a timely manner to my geocaching profile or email. Answers not received will result in deleted logs.
Questions:
- What is the vertical depth of the siltstone layer (how thick is it)?
- How tall is the fault ridge on the east side of brook?
- What caused the formation of the creek and ridges?
- Post a picture in your log with a personal item or hand in picture to prove you were there.
[REQUIRED] In accordance with the updated guidelines from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please provide a photo of yourself or a personal item in the picture to prove you visited the site.
Earth Cachers extraordinaire Stick People and BoxerBailey helped a lot in the creation of this Earthcache. Thank you!!!
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