Thursday, April 28, 2016

Death Valley National Park geology, Part III: Mesozoic through Paleogene

We made it out of the Precambrian. We made it out of the Paleozoic. We aren't nearly out of Death Valley, though. There's still about 250 million years to go, during which the valley was converted from marine property to land, became gently toasted by massive subterranean plutons, and was eventually pulled apart into the modern topography over about 15-20 million years of nonstop faulting, with volcanic eruptions and inland lakes thrown in for variety.

Thursday, April 21, 2016

And the state fossil of Minnesota is...

...nothing. Despite the map on "List of U.S. state fossils" [note, 2018/2/22: this has since been fixed], Minnesota does not have an official state fossil. There was a push to draft the giant beaver into this position, but the rodent fell short. The immediate political reason for its failure can be grasped from its scientific name: Castoroides ohioensis. Should the state fossil of Minnesota refer to another state? Certainly not!

Thursday, April 14, 2016

Death Valley National Park geology, Part II: Cambrian through Permian

When we left Death Valley National Park (DEVA) last week, we'd gotten partway through the Cambrian, into the early stages of a passive continental margin with shallow marine deposition. We return to find that predictable shallow marine deposition held sway until fairly late in the Paleozoic, when things got complicated in a hurry.

Thursday, April 7, 2016

Death Valley National Park geology, Part I: Proterozoic to Cambrian

As I mentioned a few months ago, one of the main components of my day job over the past few years has been preparing paleontological resource summaries for National Park Service Inventory and Monitoring networks. Between new and updated summaries, I've completed ten (Greater Yellowstone, Mediterranean Coast, Northern Colorado Plateau, Northern Great Plains, Northeast Coastal and Barrier, Northeast Temperate, Sonoran Desert, Southeast Coast, Southern Colorado Plateau, and Southern Plains). Each network has its own foibles and presents different challenges. Some are much more easily tackled than others; smaller parks generally have less to worry about than larger parks, with small urban cultural or historical units usually being the simplest. After finishing the Southern Plains Network last spring, I knew that the Mojave Desert Network (MOJN) would be one of the obvious candidates for the next project. It was completed under a superseded format, so it was already in the hopper, and we were already working with Death Valley National Park and Lake Mead National Recreation Area, so the iron was hot. The attraction for me was the challenge. The MOJN parks have superb geological records exposed by the combination of Basin and Range faulting and restricted plant cover, and they cover vast areas.