Paleontological Frontiers at the Florissant Fossil Beds: Princeton Expedition of 1877

I am very pleased and honored to be a part of the Western Interior Paleontological Society's Founders Symposium in 2011.  The symposium's theme is: The West that Was: Exploring Colorado's Fossil Past. The symposium will take place February 12 and 13 on the Colorado School of Mines Campus in Golden. I will present a paper that will look at Florissant's contributions to paleontology, which are enourmous.

The early days of scientific discovery at the fossil beds are amazing. One interesting story of the early days of exploration at the fossil beds is about the Princeton Expedition to Florissant in 1877. 





Early (1874) photo of a petrified stump at Florissant.





On Wednesday, July 11, 1877, the Princeton Expedition arrived at the fossil beds and later that day wrote in their journal: “We camped at Florissant —Judge Castello’s.  In the morning we set to work, all the department finding something to do . . . Dr. Brackett with Scott, Osborn, and Potter paid Mrs. Hill a visit and gained quite a lot of fossils, bugs, leaves, etc.  Lynde and Speir worked at the fish beds discovered the day before.  The fruit of the labor of the day was shared in the evening along with the mineralogists spoil.  A few petrified wood pieces were found in a gully. . . and some pretty specimens of chalcedony were the afternoon's spoil. The old Judge was quite a character and by his kindness our stay at Florissant was rendered pleasant as well as profitable.” The Princeton students collected and shipped plant fossils to Leo Lesquereux, insects to Samuel Scudder, and vertebrates to E.D. Cope. At least 180 of the plant and insect specimens the students collected became type specimens. Charlotte Hill, an early homesteader who lived at the site, provided specimens to the Princeton Expedition and then later that year to Scudder when he arrived.





Osborn on left, Scott on right. Both about 16 years old.

Prior to the expedition’s departure from New Jersey, two of the student organizers, William Berryman Scott and Henry Fairfield Osborn, met with Cope for advice on where to hunt for fossils.  From that first meeting, Osborn and Scott built a lasting friendship with Cope. Cope’s friendship and mentoring persuaded both Osborn and Scott to specialize in paleontology. Osborn and Scott maintained their professional relationship with Cope over the years.

Both Osborn and Scott returned from Florissant and their expedition completely committed to paleontology. Scott went on to be a professor of geology at Princeton, a post he held for the rest of his life. Osborn held a professorship at Columbia University and then headed the American Museum of Natural History from 1908-1933. Through Osborn’s efforts, the work of paleontologists reached world-wide expression in the museum where he balanced exploration, research, public exhibition, and publication. 

Florissant is one of the most taxonomically diverse fossil sites in the world. The lacustrine shales of the Florissant Formation have yielded around 1,700 described species of plants, insects, and spiders, as well as a few vertebrate fossils. These fossils range in size from tiny impressions in paper-thin shale to massive petrified tree stumps preserved by a lahar or volcanic mudflow. The petrified stumps are among the world’s largest in circumference. Florissant has one of the few known instances in the fossil record for the tsetse fly. Although butterflies are extremely rare in the fossil record, Florissant has yielded 12 species—more than any other fossil insect site.



USFS photo of the "big Stump" date 1900

The geology of the Florissant area is linked with the nearby Thirtynine Mile volcanic field (16 km west and southwest of Florissant), which included the coalescing stratovolcanoes of the Guffey volcanic center. Eruptions from the Guffey volcano produced lahars, ash, and pumice, all of which influenced the deposition of the Florissant Formation.

The Florissant fossil beds have been collected and studied for more than 130 years. Historic collections of Florissant fossils can be found in no fewer than 20 museums located world-wide. After years of tourist operations at the fossil beds, a large portion of the fossil deposits were protected from further exploitation by the establishment of the Florissant Fossil Beds National Monument in 1969. 

Colorado Midland Railroad Depot moved from Florissant to the fossiil beds where it served as a hotel for tourists.

Florissant’s fossils, with their high biotic diversity, preserve a latest Eocene ecosystem that existed in this area prior to the significant cooling event associated with the Eocene-Oligocene boundary. The plant and insect fossils provide information about the evolution of North American biotic communities and their response to major climate change.

A fossil record in the overlying Quaternary sediments is emerging that aids in assessing the local terrestrial paleoecology prior to the last glacial maximum. An active paleontology program at the park continues to produce new discoveries.

Blue and Rose Quartz: Nature's Special Colors

Quartz (SiO2) is a very common mineral and is found in all three classes of rocks (igneous, metamorphic, and sedimentary), in a variety of environments, and in a range of colors—including blue and pink. These two pleasing colors make these quartz specimens an important addition to a collector’s cabinet. Blue quartz is scarce while, on the other hand, rose quartz is more common. Rose quartz has a pale pink to rose red color. The color is thought to be caused by trace amounts of titanium. When samples of rose quartz from several localities were dissolved in acid, insoluble residues within the quartz were found. The residue was composed of thin microscopic fibers. These fibers may also be responsible for the color of rose quartz.

Well-formed crystals are rarely found—a true geological mystery. Most of these rare rose quartz crystals are from Minas Gerais, Brazil. Rose quartz is generally found in massive chucks associated with pegmatites (figure 1). The term pegmatite refers to the texture of certain coarse-grained crystalline granites. Since rose quartz is cloudy, it is not popular as a faceted gem but is commonly cut into cabochons (figure 2), rounded into beads for necklaces, or carved.



Figure 1. This large rose quartz specimen was found at the Devil's Hole Mine, about a mile from the town of Cotopaxi,  Colorado. Photo date 2007, © by A. Schaak.

 

Figure 2. A cabochon pendant from the same rose quartz boulder in figure 1. Photo date 2007,© by A. Schaak.

Rose quartz is the state mineral of South Dakota. Some rose quartz from South Dakota contains microscopic rutile needles which produces a distinctive asterism or a star-shaped figure of light on the surface of polished pieces. There are several good occurrences of rose quartz in Fremont County, Colorado.

Blue quartz gets it deep to sky blue color from inclusions that scatter sunlight from inclusions. These inclusions could be tiny mineral grains of: ilmenite, rutile, tourmaline, crocidolite, magnesioriebeckite, or zoisite (maybe others). Inclusions selectively scatter visible light of the shorter, blue wavelength. Blue quartz has opalescence (waxy luster), chatoyancy (alternating luster), and asterism (presence of star-like figures).


Figure 3. These blue quartz megacrystals are located in the pegmatites of the Cape Ann Granite at Andrew’s Point in Rockport, Massachusetts. Photo date 2007, © by H. Renyck.

Blue quartz occurs at a number of localities. Colorado has an occurrence of blue quartz in Park County. Small, doubly terminated crystals in a rhyolitic porphyry, informally known as Llanoite, occurs in Llano County Texas. The blue crystals weather out and can be easily collected. Blue quartz is found in Wisconsin in a diorite near the Dairyland Power Dam near the town of Tony. Recently discovered blue quartz in the Cushing Point formation of Peak’s Island, Maine has inclusions that have the chemistry of biotite. The presence of biotite in blue quartz is new—past research has not listed biotite as a possible inclusion. Research suggests that the inclusion of biotite on Peak’s Island blue quartz may be responsible for giving this quartz its blue color. Blue quartz is also located in the pegmatites of the Cape Ann granite at Andrew’s Point in Rockport, Massachusetts (figure 4).

Figure 4. Close up view of blue quartz in Cape Ann Granite at Andrew’s Point in Rockport, Massachusetts. Photo date 2007, © by H. Renyck.

References:

Coblieg, T., 1986. Why is Blue Quartz Blue?, Geological Society of America 18: 567.

Frondel, C., 1962. The System of Mineralogy, 7th edition, vol. 3, Silica Minerals, John Wiley and Sons Publishers, N.Y., 334 p.

Koivula, j., 2003,. Blue Quartz. Gems & Gemology 39, p. 44-45.

Romero Silva, J.C. 1996. Blue Quartz from the Atequera-Olvera Ophite, Malaga, Spain. The Mineralogical Record 27, p. 99-103.

Rossman, G. R., 1994. Colored Varieties of the Silica Minerals: in Silica: Physical Behavior, Geochemistry and Materials Applications, edited by P.J. Heaney, C.T. Prewitt, and G. V. Gibbs, Washington, D.C., Mineralogical Society of America, Reviews in Mineralogy, vol. 29, p. 433-468.

Wise, M. A., 1981. Blue Quartz in Virginia, Virginia Minerals 27, p. 9-13.

Zolensky, M. E., Sylvester, P.J., and Paces, J. B., 1988. Origin and significance of blue coloration in quartz from Llano rhyolite (Illanite), north-central Llano County, Texas. American Mineralogist, 73, p. 313-232.



High Park Area Yields New Tourmaline Deposit

A deposit of black, specimen-quality tourmaline has been discovered in the High Park area of Teller and Fremont County, Colorado. The deposit is located north of where Fourmile Creek drains into High Creek in Fremont County. High Park Road parallels High Creek and the tourmaline prospect.

High Park, at an elevation of 9,800 feet, is a rolling mountain grassland cut by gullies. Soil conditions, low precipitation, and cold temperatures are unsuitable for tree growth, nevertheless a few ponderosa and piñon pine dot the countryside. An occasional mule deer will wander by, and wild turkeys can be heard gobbling in nearby brush. People seldom visit the area where the tourmaline is. In the past, American Indians hunted here. Today, livestock grazing is the principal land use.

The black tourmaline occurs in a granite formation that juts out into High Creek. A huge mass of white quartz formed at one end of the granite. Embedded in the quartz are clusters of radiating crystals of black tourmaline. A number of the crystals are as long as pencils.



Black tourmaline, or schorl.  This specimen is 1.5 cm in diameter and is 6 cm long.  Photo by Mike Estlick.

The tourmaline at this deposit is known as schorl—one of the 10 members of the tourmaline mineral group. In addition to the High Park prospect’s tourmaline, a number of Indian artifacts were unearthed. The artifacts included a flint knife, several projectile points, and pieces of broken Ute pottery.

Further exploration of the prospect is planned. This area has the potential, with the application of skilled collecting techniques, to produce good mineral specimens in the future.

Dome Rock: Teller County's Scenic Rock

Dome Rock is a scenic outcrop of Pikes Peak Granite that can be seen north of Cripple Creek, Colorado along Teller County Road 1. Rising more than 800 feet from its base, Dome Rock is a classic example of an exfoliation dome that formed on Pikes Peak Granite.

Dome Rock, a Teller County landmark, is a classic example of the process of  exfoliation. 

Photo date 6/04, © S. Veatch.

Pikes Peak Granite, a plutonic rock (a rock formed at depth by crystallization of magma), was formed deep in the earth under high pressure. When the once deeply buried Pikes Peak Granite was exposed at the surface by uplift and erosion, pressure was released. Because Pikes Peak Granite is slightly elastic—just like all rocks—it expands from the release of pressure from the once overlying rocks. The expansion forms pressure release fractures (cracks) parallel to the surface of the granite and the outer layers peel off or “exfoliate”. The result is an exfoliation dome.

Water is also a part of the physical and chemical weathering at work forming Dome Rock. During the winter when water enters the cracks and freezes, the ice expands, widens the cracks, and loosens the sheets. Rainwater and groundwater contains dissolved carbon dioxide forming carbonic acid. This weak acid decomposes feldspar and ferromagnesian minerals in the granite, which also weakens the granite. The weathering of these minerals (into clay) give Pikes Peak Granite its pinkish color; other granites are much grayer.

These processes of physical and chemical weathering cause slabs of granite to break off along the pressure release fractures, forming exfoliation domes. The slabs of rock that fall off are termed exfoliation sheets. Other exfoliation domes can be seen throughout the Pikes Peak region and in other parts of the nation. Perhaps the most famous exfoliation domes in the United States are Stone Mountain, Georgia and Enchanted Rock in the Hill Country of Texas.

Florissant’s Sequoias: Redwood Giants of the Eocene

During the late Eocene large Sequoia (redwood) trees grew on terraces along an ancient river valley near present-day Florissant. Among these trees was the extinct Sequoia affinis, closely related to the modern redwoods (Sequoia sempervirens) that are now restricted to a narrow coastal region in northern Californa.


The “Big Stump” is one of the largest petrified redwood stumps exposed in
the Monument.  It measures 3.6 m tall and is 3.7 m in diameter at breast height. 
This stump is all that remains of a tree that was more than 90 m tall
when the mudflow buried its base.  Image date Nov 2003 by S. Veatch.

 More than 34 million years ago a lahar or volcanic mudflow, coming from a nearby volcanic center, flowed into the Florissant valley. The mudflow was up to 5 meters deep and quickly surrounded these giant trees. The upper section of the redwoods decayed and rotted away while the lower 5 meters were protected by the silica-rich mudflow. The unhurried progression of petrification—through a process known as permineralization—preserved the remains of these ancient trees with incredible detail, including tree rings.

Tree rings, which record annual growth, also reveal the growing conditions of trees. A researcher at the Florissant Fossil Beds National Monument carefully measured tree rings in fossil wood (Sequoioxylon pearsallii) and noted a larger (40%) average tree-ring width than the modern redwoods (Sequoia sempervirens) and giant Sequoia (Sequoiadendron giganteum) growing along the northern California coast. The significant difference in mean ring width between modern and extinct redwoods suggests the ancient redwoods in the Florissant Valley were growing under more favorable conditions than their modern counterparts.
It is thought that there was more precipitation, from moist Pacific Ocean air,that reached the western interior as the Sierra Nevada mountains of California had not yet been uplifted to block the flow of moist air. More precipitation, resulting from these moist air masses, would have fallen during the growing season.

Precipitation at Florissant during the late Eocene is estimated at about 50 – 80 centimeters of annual rainfall, greater than the modern precipitation of 38 centimeters. A higher level of atmospheric CO2, perhaps twice that of modern levels, may have contributed to the favorable growing conditions in the Florissant Valley of the late Eocene.

A subsequent volcanic mudflow moved across the ancient paleovalley, forming a dam of mud, rocks, boulders, and associated debris. A stream, running over earlier mudflows, began to back up behind the mud dam, eventually forming a large lake—Lake Florissant. Leaf and insect fossils were preserved in this lake.

Not only are the Sequoia stumps preserved, but Sequoia cones and foliage are also represented in the fossil record at Florissant. The cones and foliage are found separated from the tree, and have a separate classification from the fossil wood. Sequoia affinis cones are found as fossils in the thinly bedded shales of ancient Lake Florissant. The ovoid cones are made of spirally arranged scales and tend to be smaller (about two-thirds the size) than the modern coast redwood cones.

Fossil branches of the Florissant redwood, Sequoia affinis. 

Specimen FLFO-4858 from the collection of Florissant Fossil Beds National Monument. 

Image date Oct 2003 by S. Veatch.

Sequoia affinis cones. Specimen FLFO-4717 from

the collection of Florissant Fossil Beds National Monument. 

Image date Oct 2003 by S. Veatch.