The Places

Lots of camping, lots of rocks, tons of fossils, and only a couple of showers

Field trips like this never work exactly as planned due to logistical and weather problems, not to mention more discussion at an outcrop than anticipated. Thus a detailed description of each stop is not given. We always try to pack in as much as we can.

SATURDAY:
Everyone met at the Colorado Springs airport, vans were loaded and we departed. We made a stop or two within Colorado Springs before proceeding to the campground near Florissant.

SUNDAY:
To start the day we examined 1.7 billion year old Precambrian rocks of the Front Range. We examined how we can deduce relative time by observing cross-cutting relationships.

Florissant fossil beds National Monument: 35 million years ago volcanic eruptions buried the valley in a thick layer of ash and beautifully preserved the local flora. Then a lake formed in the valley and slowly sediments accumulated, burying insects, teeth, shells, or plants, that settled to the bottom, later forming into a hard shale. We visited this site and examined the superbly preserved fossils. We made several additional stops before proceeding to Pueblo Lake state park where we camped Sunday night.

As we headed south on I-25 toward Pueble Colorado, we passed through the Pierre Shale. This is a distinctive Late Cretaceous unit consisting mostly of black shale. About midway to Pueble we noticed conical outcrops approximately 60m wide to 10m tall. These hills were the Tepee Buttes, and were thought to be limestone capped resistant concretions in the Pierre Shale. Closer analysis of their lithology, geochemistry, and their fossil biota indicate an extremely interesting origin and we visited them Monday morning.

MONDAY:
At Pueblo Lake state park we explored the unusual surrounding stratigraphy.

The Dakota formation unit marks the oldest Late Cretaceous unit (95-93 Ma) and is comprised of rocks deposited in a near-shore environment.

The next younger unit is a gradational contact of alternating older Graneros Shale and younger Greenhorn Limestone. We noted how the outcrop alternates from shale to limestone and foes not express a single linear contact between the two units. From the background section on rock types and depositional settings, why might this be the case? How were these rocks deposited? There should be visible fossils in the shale units.

The Fort Hays Limestone is older (90-88 Ma) than the Pierre Shale we drove through on I-25. We noted the differences in the fossil clams at this site compared to the Greenhorm Limestone.

Visited Tepee Buttes. We made several stops as well as saw spectacular scenery on our way to Trinidad state park where we spent two nights.

TUESDAY:
We spent the morning examining several outcrops of the K/T boundary in detail.

In the afternoon we drove south into New Mexico to visit Capulin Colvano National monument. Capulin volcano is a nearly perfectly-shaped cinder cone that stands more than 1,200 feet above the surrounding plains. The volcano erupted ~60,000 years ago. Lava from surrounding vents covered almost 16 square miles. A 2-mile paved road spiraling to the volcano's rim makes Capulin one of the most accessible volcanoes in the world.

WEDNESDAY:
Left Trinidad state park and continued north on I-25 to Dinosaur Ridge. The ridge exposes spectacular Jurassic and Cretaceous sedimentary features, fossils, dinosaur footprints and bones. From the visitor's center we followed a self-guided tour throughout the Landmark.

I-70 roadcut: This is spectacular road-cut exposing a thick section of Jurassic and Cretaceous rocks. The state of Colorado has developed the roadcut for geologic field trips.

THURSDAY:
We visited a new outcrop of the K/T boundary exposed east of Denver. It contains abundant fossils, the fireball layer and volcanic ash beds.

The second activity was to travel to the Denver Museum of Natural History. Kirk Johnson gave us a backstage tour of the museum and a tour of parts of the museum.

FRIDAY:
Returned to Boston