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Dive Dry with Dr. Bill

#673: You Old Fossil You!

I can remember a few decades ago when Packy & Wendy's kids referred to me as an old fossil or an old geezer. Heck, I was a mere kid back then. But today's column isn't about me... it's about the fossils of other critters from the distant past. Yep, even before I was born!

Like most children, I was interested in dinosaurs and other critters from Earth's early history. My elementary school parking lot was made of crushed limestone and I often found fossil crinoids embedded in it. Then, while at Harvard, I took a course in invertebrate paleontology co-taught by the soon-to-be-famous Stephen Jay Gould. Since I was already interested in the echinoderms such as sea stars and sea urchins, I undertook a project to review the fossil collection of that phylum in the university's Museum of Comparative Zoology. While rummaging through a drawer of uncataloged specimens, I came across a fossil helicoplacoid that had not been described scientifically.

Whoopee... I discovered a "new" (or rather very old) species. These were among the earliest echinoderms, dating back to the dawn of invertebrate life about 570 million years ago. They had a body somewhat like a sea cucumber but covered in a series of spiral plates for defense. As a Harvard junior, I wasn't considered adequate to the task of actually describing and naming the species. That honor went to J. Wyatt Durham at the University of California, Berkeley, Museum of Paleontology.

When I arrived here on Catalina after graduation, I learned that there were some fossil bearing rock layers on the island. Unfortunately erosion due to decades of goats and other grazing animals had probably destroyed many of the exposed formations. I did take my students on field trips to places like Fossil Peak and Mount Orizaba looking for fossils, and was certainly aware of the white cliffs of Two Harbors formed by fossilized diatoms. Why is this important? Because it presents scientific evidence that our island was once underwater... and would have been an even greater diver's paradise back in ages past!

Back in the late 1960s when I was an undergraduate, I worked with my mentor Dr. H. B. Fell on an early computer-based project to try to disprove the notion of continental drift. Back then I couldn't simply program my laptop to crunch the data we used. It took a computer the size of a railroad locomotive and hours of punching IBM cards to run a simple computation. Of course the hypothesis we worked on back then was wrong and what is now known as plate tectonics became the accepted theory. It was a good lesson in science... learning to adjust one's beliefs to the data rather than the data to fit one's beliefs.

The movement of the North American and Pacific plates in our region has created pressure that slowly pushed our island up out of the ocean. According to at least one researcher it may be settling back down, although I expect my Social Security payments will be long past three million years from now when he predicts Catalina will be submerged again. Rather than predict the future, I'm going to dwell on our history. From the few fossil bearing layers left on the island, we know it was once like the grades some of my students at Toyon received... below "C" level.

One of the fossils that has been identified in the sedimentary limestone layers on Fossil Peak and Mountain Orizaba is that of a scallop known scientifically as Pecten estrellanus. This is not a species that would be served up to you on a dinner plate at The Lobster Trap. Since it is fossilized, it has what Turtle Wax would refer to as a "hard shell finish." The soft edible parts have "gone the way of all flesh." These bivalves lived during the Miocene Epoch, five to 23 million years ago. I may be considered a fossil by some, but I was definitely not around back then... at least not in my current incarnation.

More evidence of the island's former residence at the bottom of the sea can be seen by anyone boating past the Blue Cavern-Big Fisherman Cove area near Two Harbors. Relatively thick beds of white sedimentary rock are exposed there along the coast. These are composed of dead diatoms, a group of photosynthetic organisms that some still classify as algae while others place in an entirely different group. They are important members of the phytoplankton or plant plankton. When they die, their protective shells fall to the ocean floor in great numbers and form an ooze that eventually gets compressed into sedimentary rock. Then, when the former ocean floor is exposed by uplift, we see the sedimentary layers.

I've never been much of a geologist, so I'm unclear about something. I hear many refer to the "White Cliffs of Two Harbors" as limestone, yet they are composed of diatoms which have silicon-based shells. The White Cliffs of Dover, which I saw the year before I moved to the island were formed from another type of phytoplankton known as a coccolithophore. This group does have calcium carbonate plates and therefore would form what I would consider a true limestone. The formations on Fossil Hill and Mt. Orizaba are also calcium carbonate based limestone. Yet geologists do refer to our diatom-based formation as diatomaceous limestone. I'm beginning to wonder if they don't have rocks in their heads!

© 2016 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Fossil Helicoplacus from Harvard daze and diatomaceous limestone at Blue Caverns;
rock with scallop fossils (courtesy of Yvetta Williams) and actual scallop fossil..

This document maintained by Dr. Bill Bushing.
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