Oakes Quarry Park

20111230-130852.jpg

Administrative duties and exhibits have kept me away from the blog for the last few weeks. I somehow found the time to take an actual non-working (mostly) vacation this week (my first one in years), and that’s given me a chance to catch my breath and focus on the blog a bit.

Just before Christmas I made a trip to Indiana to pick up a specimen (more on that in a future post), and while I was there Andy Moore took us on a visit to Oakes Quarry Park near Dayton, Ohio. Ohio has several fossiliferous quarries that have been turned into educational parks, which I think is an excellent practice that other states should consider emulating.

The Oakes Quarry Park exposes about 8 meters of the the Silurian Brassfield Formation, a fossil-rich limestone and dolostone. The quarry floor is a dolostone that is absolutely riddled with burrows:

20111230-131228.jpg

The wall of the quarry exposes several other units, including a crinoidal limestone made up mostly of broken crinoid fragments:

20111230-131654.jpg

There are finer-grained units that include a variety of fossils, including gastropods and nautiloid cephalopods:

20111230-132014.jpg

There are also limestone beds that are filled with rugose and tabulate corals:

20111230-132448.jpg

20111230-132540.jpg

20111230-132613.jpg

As you may have expected, the different units are not distributed at random through the quarry, but occur in a particular sequence. In the marked up image below, the blue represents the burrowed dolostone (not visible in this image), the red is the crinoidal limestone, the green are the fine-grained beds that include nautiloids, and the yellow are the coral-rich limestones:

20111230-134202.jpg

This seems to represent a transgressive sequence, in which the water was getting deeper over time. The burrowed dolostone is probably an intertidal deposit which was actually exposed (or nearly so) at low tide. As the water got somewhat deeper, this spot became the surf zone right along the beach. The high wave energy carried broken fragments of various organisms, especially crinoids. Crinoids are delicate animals that have skeletons made up of hundreds of individual pieces that will quickly disassociate under high-energy conditions.

Above the crinoidal limestones are slightly deeper-water conditions. There is some variation here; the finer-grained beds are probably the deepest water, and may have been below normal wave base, while the coral-rich units were almost certainly above wave base (but still subtidal). The alternating occurrence of these units probably represents slight changes in local sea level. This didn’t have to be due to actual regional changes in sea level; it could easily be the result of the migration of coral reefs as they grew across the sea floor, with the water getting shallower when the reef is present because of the thickness of the reef.

There’s one more interesting piece of this story. At the top of the quarry the corals are all beveled off:

20111230-135647.jpg
All the exposed rock around the top of the quarry is polished, and in most areas it’s covered with striations:

20111230-135851.jpg
During the Pleistocene, glaciers covered this area, stripping away the younger sediments and grinding away the top of the coral-rich limestone. So, on a single surface, we have evidence for a tropical coral reef and a continental glacier, separated by over 430 million years.

This entry was posted in General Geology, Invertebrate Paleontology. Bookmark the permalink.

4 Responses to Oakes Quarry Park

  1. Tony Edger says:

    Wonderful conclusion to the post – an amazing juxtaposition of climates and time periods. Thank you.

  2. altondooley says:

    Brett and I have taken some gigapans at Oakes Quarry:

    A section of the quarry wall:
    http://gigapan.com/gigapans/106554
    iOS version:
    http://gigapan.com/mobile/iOS/1.0/?id=106554
    Part of the coral reef:
    http://gigapan.com/gigapans/106731
    iOS version:
    http://gigapan.com/mobile/iOS/1.0/?id=106731

  3. Thanks for posting this! I’m talking about mining in my geology class and the nearest reclaimed surface mine we have access to is Oakes Quarry. Sarah Fortner, Wittenberg

  4. altondooley says:

    @Sarah Fortner: We’re working on a virtual field trip for iPad, downloadable from iBookstore, about Oakes Quarry that should be available later this year; we’re doing a poster about it at GSA in Charlotte next month. I’ll announce on the blog when it becomes available.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s