Incredible New Fossils Acquired for the Department! But...

During our field trip last weekend, we stopped briefly at a mineral show in the Sierra foothills. I wasn't going to buy anything, but then I saw some specimens that made my jaw drop, and they were available for an incredibly low price. I couldn't resist adding these beautiful pieces to my teaching collection at the college.

The first was a giant trilobite fossil from Morocco. Trilobites were ancient arthropods, among the first of the complex lifeforms to inhabit the Paleozoic seas. They had brains, eyes, legs, and survived in numerous different habitats. But most trilobites are very small, maybe an inch or two long. This monster was huge! And the seller was willing to part with it for only $30! I snapped it up.

I was headed back to vehicles when I saw the second incredible specimen. It was the tooth of a Mosasaur, one of the most terrifying predators in the Mesozoic seas. It was even in matrix, along with a fragment of the jawbone. And for just $12, how could I pass it up? Another specimen purchased.

Why the excitement over a Mosasaur? It's because they were one of the most interesting creatures ever found in our region. A local boy found the fossil in the foothills of the Coast Ranges just twenty miles or so from our campus. We've already acquired a skull of the 30-foot long creature for demonstrating our local paleontology finds.

An old dinosaur, along with a Mosasaur skull replica

I know some of you are already squirming just a little bit wanting to tell me that I was duped, and the fossils I purchased are fakes. Actually I already knew that. There's an old adage that if it's too good to be true, than it probably is. Producing fake specimens is an art that began just minutes after fossil collecting became "a thing" several hundred years ago. The trilobites and ammonites coming out of Morocco are particularly egregious examples. Genuine specimens have come from the region, but they are relatively rare and very expensive. Plenty of nearly worthless fragments exist, and people soon found they could mount partial and broken specimens in a matrix and sell them for a decent price. I imagine quite a few people have managed to eke out a living doing so.

If dealers were honest about such things, it wouldn't bother me too much. I wanted a large trilobite replica that I could use while discussing paleontology, and this specimen fit the bill pretty well. The ironic thing is that the dealer clearly marked some of his specimens of smaller trilobites as "copies", but he basically told me "why buy these smaller fakes when you could have the real thing right here for only $30?" As a replica, the price was pretty cheap. A genuine sample of this size could probably run into four figures, and sometimes these fakes carry such price tags. That's a pretty handy profit margin, courtesy of some poor uninformed person with too much money on hand.

The tooth is most likely the real thing, but was probably damaged on the back side. The root is probably left over from the faker's lunch, a piece of cow or sheep bone glued to the tooth. Sometimes they make entire jaw bones out of this stuff.

If you want to see our latest genuine fossil acquisition, here it is: plant fragments in a slab of sandstone. It's remarkable because it comes from the Western Metamorphic Belt of the Sierra Nevada, and metamorphic rocks don't often preserve fossils, but it happened here. It dates from the Jurassic period, a time when dinosaurs wandered the nearby landmass. Leaves and fragments of wood flowed into the nearby shoreline and came to be preserved in the sandy layers.

How do I know it is genuine? Well, I found it myself. That's the best way to confirm such things, and it's fun to boot.

For more information about these faked specimens, check out http://www.fossilmuseum.net/collect/fake-trilobites.htm

Accretionary Wedge Carnival #30: The Bake Sale

OK, I'm not a baker, I'm not a cake-maker, but I can eat with the best of 'em. This month's Accretionary Wedge, hosted by Callan Bentley at Mountain Beltway, is on a delicious topic, food! Educational food, no less...

I hereby challenge my fellow geobloggers (and any newbies who want to participate) to explore the interconnections between geology and food. This can take any form you want, but I’m really hoping for some edible, geologically accurate models. Yummy stuff that illustrates and informs about earth science? Yes, it is possible!

The end of the semester in my historical geology class is usually accompanied by a social gathering, and an interesting cake is usually in the mix. The picture above was a complicated mess befitting of the subject, an ocean-continent convergent boundary, i.e. a subduction zone. The brown is the region of a magmatic arc, where magmas rise to the surface forming a series of andesitic stratovolcanoes (the red glob on the right is the molten rock!). The yellow strip is the forearc basin, a shallow sea where sediments form thick layers. The only piece I can't make out specifically is the accretionary wedge, unless the blue is not ocean water (ironic, given the name of the carnival). I'm not sure how to interpret the rest of the layers, but I can report that they were tasty!

Edible education took a different turn a number of years ago when I had the chance to see Walcott's Burgess Shale quarry in British Columbia (one of my very first blogs was on the subject). The site is considered to be one of the most important fossil discoveries in the world as it yields up thousands upon thousands of soft-bodied Cambrian animals. This is important because usually only hard-shelled creatures are ever preserved. The Burgess fauna gives us a glimpse of the complete ecosystem that existed at the "dawn" of complex life around 510-515 million years ago.

As one might expect, the quarry is carefully protected, and collecting could actually land you in jail. So we thought it interesting that our guide promised that we would all get a trilobite of our own if we survived the six-mile hike to the quarry. The "trilobites" are below!

Time Beyond Imagining - A Brief History of the Colorado Plateau, Part 3: LIFE!

Fossils! Do you remember that first moment that you found a fossil as a child? Or did you never have that experience? I vividly remember exploring a meadow on the Kaibab Plateau north of the Grand Canyon as a 10-year-old. I didn't know what they were at the time, but later learned that they were disks from crinoid stems and sponges from the Permian seas 300 million years ago. I was impressed; I was not even disappointed that they weren't dinosaurs. I can look back and see this moment as one of the seminal events that led to my choice of geology as a field of study.


All kids go through a fossil phase. I also know that most geologists and paleontologists simply never outgrew it. And so it is that today's post is about fossils. Particularly the earliest complex life that evolved on our planet.

600 million years ago (give or take, what's a few million years between friends?), the continents of the world were in the process of splitting and breaking up. Many laypeople have heard of Alfred Wegner's Pangea, but we are not talking about that particular supercontinent (although we will in a later post). The continent that existed around a billion years ago has been named Rodinia. Such continents seem to be unstable, perhaps due to the buildup of heat from underneath. The land is pushed upwards in vulnerable places, the continent splits, and new seas are formed. As the continents move further apart, they subside and the shorelines around the margins of the continent invade the land. All over the world, the seas were transgressing across continental surfaces, forming shallow epicontinental seas (I am guessing that Hudson Bay comes closest in today's world as an example).


The split in North America cut across the southeastern part of California, and through central Nevada. During the Cambrian Period, the transgressing seas covered most of the southwest, with the exception of a portion of Utah called the Transcontinental Arch. The region was located close to the equator, so the ingredients were there for life: nutrients, shallow water, warmth. Life was about to get a whole lot more complex than the single-celled organisms that had existed for billions of years. The details are for other experts to describe, but multi-celled life appeared, and thrived.


Look at the picture of the Grand Canyon. Down in the depths there is a prominent terrace called the Tonto Platform. The platform exists because the Bright Angel Shale cannot form cliffs for very long, being easily eroded. Just below lies a cliff of Tapeats Sandstone, and above are a few slopes and ledges of the Muav Limestone. These three formations, sand, shale and limestone, record the invasion of the shallow sea across the Grand Canyon region.


Pick up enough fragments of the Bright Angel Shale, and you may be lucky enough to find the signs of the explosion of life that swept across the planet around 540 to 500 million years ago. Worm trails and burrows are plentiful, but the prizes will be the discarded exoskeletons of trilobites.


Trilobites are arthropods in the same phylum as the insects, crustaceans, arachnids and other jointed-legged creatures. Because they were one of the first animals to possess a hard shell, their fossils tend to dominate the fossil record, even though a large number of soft-bodied animals were doubtlessly around (see one of my first posts). They walked and burrowed in the sediments of the ocean floor; some grazed on algae, some were mud processors, some may have been predators. They ranged in length from a quarter inch to one monster that exceeded three feet in length. Their closest living relatives are probably the horseshoe crabs (see this NOVA geoblog article). Some were capable of rolling up like pill-bugs to protect themselves. They grew by molting, so not every discovery is a dead creature, simply a cast-off shell.


Other early creatures included brachiopods, sponges, and strange cone-shaped archaeocyathids, which may have been distantly related to corals.