While Geocaching in the area, I came accross this unique geologic location. A large peice of sandstone full of carbonate rich shell fossils. Pretty cool spot for the kids who want to see really cool fossils! So, let me explain the type of rock and fossils are here.
At the above coordinates, you will see a large piece of sandstone which is a type of sedimentary rock. A sedimentary rock is made of smaller fragments from other types of rocks (could be other sedimentary rocks, or it could be igneous or metamorphic). In this case, sand grains make up the rock. There are two types of sandstone desposits. A marine sandstone deposit was formed close to the shore (or part of the shore like a beach). These often contain shell and other marine fossils. A terrisatial sandstone deposit formed from a large desert sand dunes. Some examples include the large sandstone deposits of Arizona and Utah. These contain no marine fossils and are much thicker in size.
The sandstone was burried under more and more sediment where it was compressed and heated to fuse the sand grains together. This left imprimpts where the shells once were, leaving behind molds of fossils. This rock was likely sourced locally as this entire part of Orange County was under water about 10 million years ago.
Now for something a little more advanced. For certain fossils, geologist can tell the direction in which the rock formed in. For example, is the rock right-side up? Or is it upside down? Simple fluid mechanics can help answer this question. Think of a concave fossil with a "bumb". If an animal with a concave shell dies, its shell will fall to the ocean floor (in this case near a sandy beach). The ocean waves will move that shell to a more stable position. For example, a shell is more stable and less willing to move if the shell has its "bump" facing upward (concave down). If a geolgist sees an impression of a shell that has its bump pointing a certain direction, a geologist can almost certiantly tell which way the rock originally had formed. This will help geolgists know if the rock was deformed (such as being twisted or folded) since it formed. The image below shows fossils in the concave down (bump up) position and show that the rock had originally formed out of the page. This means, from the camera, we are looking down on the rock as it originally had formed. The rock here is right-side up becuse the fossils are concave down ("bum" up).
TO LOG A FIND ON THIS CACHE YOU MUST ANSWER ALL THE QUESTIONS BELOW. YOU CAN CONTACT ME THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER TO SEND YOUR ANSWERS. ANY INCORRECT ANSWERS MAY RESULT IN A CLARIFICATION RESPONSE FROM ME.
1. "Chiquita Canyon Fossils" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching.
2. Take a close up picture of your favorite fossil and upload it to the cache page.
3. How large are the fossils here? How abundant are they?
4. Look around at the shells in the sandstone. Is this rock rightside up or upside down? How can you tell? This question may be hard to answer, so be sure to read the last paragraph in the description above and use the photo to help guide you.
5. Based on the types of fossils here what type of environemnt might this have formed in? (For example, a lake, river, pond, channel, shallow marine, beach, reef, deep marine, desert sand dunes, etc).
Works Cited
https://www.unearthedstore.com/products/fossil-pecten-shells-france