Florissant Fossil Beds National Monument 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2006/009 

National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 

Florissant Fossil Beds National Monument 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2006/009 

Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, Colorado 80225 

March 2006 

U.S. Department of the Interior 

Washington, D.C.
The Natural Resource Publication series addresses natural resource topics that are of interest 

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series include vital signs monitoring plans; "how to" resource management papers; 

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Printed copies of reports in these series may be produced in a limited quantity and they are 

only available as long as the supply lasts. This report is also available from the Geologic 

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gre_publications) on the internet, or by sending a request to the address on the back cover. 

Please cite this publication as: 

KellerLynn, K. 2006. Florissant Fossil Beds National Monument Geologic Resource Evaluation 

Report. Natural Resource Report NPS/NRPC/GRD/NRR—2006/009. National Park Service, 

Denver, Colorado. 

NPS D-37, March 2006 
FLFO Geologic Resource Evaluation Report iii 

Table of Contents 

List of Figures .............................................................................................................. iv

List of Tables ................................................................................................................ iv

Executive Summary ...................................................................................................... 1

Introduction ................................................................................................................... 3

Purpose of the Geologic Resource Evaluation Program ............................................................................................3

Geologic Setting .........................................................................................................................................................3

Geologic Issues............................................................................................................. 5

Protection of Paleontological Resources ....................................................................................................................5

Preservation of Fossil Stumps....................................................................................................................................6

Estimates of Paleoelevation .......................................................................................................................................6

Development ..............................................................................................................................................................7

Dam Removal and Stream Restoration ......................................................................................................................8

Agricultural Terraces ..................................................................................................................................................9

Abandoned Mine Land Site ........................................................................................................................................9

Mining.........................................................................................................................................................................9

Potential Research ...................................................................................................................................................10

Geologic Features and Processes............................................................................. 17

Evolution and Global Climate Change......................................................................................................................17

Late Eocene Erosion Surface...................................................................................................................................17

Paleontological Resources .......................................................................................................................................18

Unconformities..........................................................................................................................................................20

Tors ..........................................................................................................................................................................21

Sedimentation and Fossilization...............................................................................................................................21

Map Unit Properties .................................................................................................... 23

Map Unit Properties Table........................................................................................................................................24

Geologic History.......................................................................................................... 25

References................................................................................................................... 27

Appendix A: Geologic Map Graphic .......................................................................... 31

Appendix B: Scoping Summary................................................................................. 33 

Attachment 1: Geologic Resource Evaluation Products CD 
iv NPS Geologic Resources Division 

List of Figures 

Figure 1. Geologic Time Scale.......................................................................................................................................4

Figure 2. Abandoned Mine Land Site...........................................................................................................................13

Figure 3. Agricultural Terrace West of Hornbeck Homestead. .....................................................................................14

Figure 4. Dam Removal and Stream Restoration.........................................................................................................15

Figure 5. Regional Map of Central Colorado................................................................................................................16

Figure 6. Preservation of Fossil Stumps. .....................................................................................................................16

Figure 7. Tree Growth Rings of Petrified Wood. ..........................................................................................................22

List of Tables 

Table 1. Factors that Affect the Stability of In Situ Paleontological Resources ............................................................11

Table 2. Estimates of Florissant Paleoelevation ..........................................................................................................12

Table3. Structure Cut and Fill Volumes........................................................................................................................12
FLFO Geologic Resource Evaluation Report 1 

Executive Summary 

This report has been developed to accompany the digital geologic map produced by Geologic 

Resource Evaluation staff for Florissant Fossil Beds National Monument in Colorado. It 

contains information relevant to resource management and scientific research. 

The purpose of Florissant Fossil Beds National 

Monument, as stated in its enabling legislation, is: “To 

preserve and interpret for the benefit and enjoyment of 

present and future generations the excellently preserved 

insect and leaf fossils and related geologic sites and 

objects.” Other legislation affecting the national 

monument includes the Organic Act of 1916, the National 

Environmental Policy Act, the National Historic 

Preservation Act, and the Endangered Species Act. 

Florissant Fossil Beds National Monument is significant 

for: providing recreational and educational 

opportunities, providing wildlife habitat in a developing 

region, acting as stimulus to the regional tourism 

economy, preserving natural solitude and beauty, 

maintaining the absence of light pollution, and 

preserving cultural resources. Its primary goal is to 

preserve, protect and interpret its paleontological 

resources and geologic significance. 

• The Florissant Formation contains one of the largest 

varieties of fossil Arthropods (insects and spiders) 

found anywhere in the world. 

• The abundance of finely detailed dragonflies, beetles, 

ants, butterflies, flies, fish, plants, ferns, leaves, pollen, 

flowers, mammals, and birds and the enormity of the 

petrified redwood stumps evoke a sense of wonder for 

visitors. 

• The ancient Florissant ecosystem furnishes critical 

evidence regarding the environment during the late 

Eocene Epoch, which is important in the global 

interpretation of biologic and climatic change and 

tectonic and uplift chronologies. 

• Florissant’s 34- million- year- old ecosystem, which 

immediately preceded a very significant cooling of the 

world’s climate, impacts the national debates on 

evolution and global climate change. 

• The newly hypothesized mode of exceptional fossil 

preservation (i.e., diatom mats) at the monument could 

have far- reaching implications for other lacustrine 

sites. 

• The monument provides unparalleled paleontological 

research possibilities by virtue of its high 

concentration of indigenous plant and animal species 

that lived 34 million years ago. 

• Opportunities exist to research, compare, and contrast 

ancient ecosystems with the present, providing 

insights to our current ecological dilemmas. 

• Buried within the Florissant Formation, sediments and 

delicate fossils provide future research opportunities 

for paleontologists using methods and skills not 

existing today. 

In addition to Florissant’s exquisite paleontological 

resources, other geologic features and processes include: 

• The late Eocene erosion surface, which is significant 

for reconstructing the erosional, climatic, and tectonic 

history of the southern Rocky Mountains; 

• Tors formed beyond the limit of glaciation and 

important for interpreting the glacial history of the 

region; and, 

• Unconformities are significant for understanding the 

span of geologic time and the processes that shape the 

earth. 

Lastly, geologic issues of significance for resource 

managers at Florissant include: disturbed lands, 

agricultural terraces, removal of dams and restoration of 

streams, and past and present mining activity in the area. 

The following geologic issues may warrant attention 

from resource managers: 

• Development—Management concerns arise from 

possible impacts on natural resources from rapid 

subdivision development adjacent to the monument 

and the anticipated increase in visitor use. These 

concerns include preservation of current viewsheds 

and lightscapes and the protection of water resources. 

Also, any development within the monument requires 

attention to paleontological resources, especially 

undiscovered buried stumps. 

• Water Resources—With many unknown factors 

regarding water resources (e.g., locations, number, and 

quality of wells, seeps, springs, and streams) a need 

exists to inventory, assess, and monitor the water 

resources of the monument, as well as to develop a 

water resources management plan. 

Research Opportunities: 

• Investigators have long speculated about possible 

sources of pumice and ash of the Florissant Formation, 

but have not studied the sources conclusively. 

Information gained from a study is significant for 

scientific interpretations and the monument’s 

interpretive program. 

• Florissant represents the world’s most significant 

upland fossil deposit from the Eocene- Oligocene 

transition (33–34 million years ago), immediately 

preceding a global cooling event. Collecting fossil leaf 

assemblages from several stratigraphic levels at 

different sites around the Eocene Florissant lake basin 

would provide new evidence to interpret the smallscale variability of biotic communities and 

microclimatic conditions around the lake basin in time 

and space. A comparison of Florissant fossils with the 
2 NPS Geologic Resources Division 

fossil plants from other localities will provide an ideal 

basis for studying the impacts and nature of climate 

change over a wide geographic area. 

• Paleoelevation Estimates—Most of the recent 

estimates of Florissant’s elevation during the late 

Eocene range from 6,235 feet (1,900 m) to 13,450 ft 

(4,100 m). The most important point to emerge from 

the numerous studies conducted during the 1990s is 

that paleoelevation appears to have been much higher 

than originally estimated by MacGinitie in 1953, which 

served as the benchmark for decades. 

• Preservation of Fossil Stumps—Because the exposed 

fossil stumps are a primary park resource and the only 

paleontological resource that can be seen easily by 

visitors along the trails, reburial is not an option for 

preservation. Nevertheless, exposure to the elements is 

deteriorating this valued resource. However, the 

results of recent investigations, using techniques and 

methods from cultural conservation of historic 

buildings and gravestones, may help seal the stumps 

and reduce spalling of pieces of petrified wood. By 

proactively identifying and preserving the stumps, 

opportunities for further vandalism and theft would 

diminish. 

• Protection of Paleontological Resources—Florissant 

Fossil Beds has a pro- active program to educate 

visitors on the scientific importance of in- situ fossil 

materials in the park. Park staff work vigilantly with 

law enforcement officials and museums to protect 

paleontological resources and recover stolen fossils. 

Additionally, in order to monitor paleontological 

resources, the National Park Service has established a 

system of measurable indicators of change to resource 

conditions. The strategy includes assessment of 

climatological data, rates of erosion, human activity 

and behavior, and site monitoring of destroyed (lost) 

or exposed (gained) fossils at the surface. 
FLFO Geologic Resource Evaluation Report 3 

Introduction 

The following section briefly describes the National Park Service Geologic Resource 

Evaluation Program and the geologic setting of Florissant Fossil Beds National Monument. 

Purpose of the Geologic Resource Evaluation Program 

Geologic features and processes serve as the foundation 

of park ecosystems and an understanding of geologic 

resources yields important information for use in park 

decision making. The National Park Service Natural 

Resource Challenge, an action plan to advance the 

management and protection of park resources, has 

focused efforts to inventory the natural resources of 

parks. Ultimately, the inventory and monitoring of 

natural resources will become integral parts of park 

planning, operations and maintenance, visitor 

protection, and interpretation. The geologic component 

is carried out by the Geologic Resource Evaluation 

(GRE) Program administered by the NPS Geologic 

Resources Division. The goal of the GRE Program is to 

provide each of the identified 270 “Natural Area” parks 

with a digital geologic map, a geologic resource 

evaluation report, and a geologic bibliography. Each 

product is a tool to support the stewardship of park 

resources and is designed to be user friendly to nongeoscientists. 

GRE teams hold scoping meetings at parks to review 

available data on the geology of a particular park and to 

discuss specific geologic issues affecting the park. Park 

staff are afforded the opportunity to meet with experts 

on the geology of their park during these meetings. 

Scoping meetings are usually held for individual parks 

although some meetings address an entire Vital Signs 

Monitoring Network. 

Bedrock and surficial geologic maps and information 

provide the foundation for studies of groundwater, 

geomorphology, soils, and environmental hazards. 

Geologic maps describe the underlying physical habitat 

of many natural systems and are an integral component 

of the physical inventories stipulated by the National 

Park Service (NPS) in its Natural Resources Inventory 

and Monitoring Guideline (NPS- 75) and the 1997 NPS 

Strategic Plan. The NPS GRE is a cooperative 

implementation of a systematic, comprehensive 

inventory of the geologic resources in National Park 

System units by the Geologic Resources Division, the 

Inventory, Monitoring, and Evaluation Office of the 

Natural Resource Program Center, the U.S. Geological 

Survey, and state geological surveys. 

For additional information regarding the content of this 

report, please refer to the Geologic Resources Division of 

the National Park Service, located in Denver, Colorado 

with up- to- date contact information at the following 

website: http://www2.nature.nps.gov/geology/inventory/ 

Geologic Setting 

Past geologic studies have considered the age of the 

deposits at Florissant to be Pliocene, Miocene, 

Oligocene, or Eocene (figure 1). MacGinitie (1953) made 

the first reliable age determination from his study of 

fossil plants and other fragmentary evidence of fossil 

mammals. In 1992 a field crew from the University of 

Colorado Museum found fragments of a brontothere, 

which in addition to other previously discovered 

mammal fossils (i.e., Merycoidodon [oreodont], 

Mesohippus [horse], and Peratherium [mouse opossum]), 

indicated that the Florissant Formation is late Eocene age 

(Evanoff and de Toledo, 1993). In 2003 a systematic 

investigation greatly increased the known mammal 

diversity from the Florissant Formation (Worley, 2004). 

The co- occurrence of these fossils places the deposition 

of the Florissant Formation at the same time as the 

Chandron Formation in Badlands National Park, which 

occurred at the very end of the Eocene Epoch. In 

addition, an 40Ar/39Ar age of 34.07 ± 0.10 million years 

supports a Late Eocene time frame (Evanoff and others, 

2001). 

The Eocene rocks at Florissant Fossil Beds National 

Monument contain fragile insects, tree foliage, and other 

forms of life, which are completely absent or extremely 

rare in most paleontological sites. According to Meyer 

(2003), the fossil- bearing shales have yielded more than 

40,000 specimens that contain more than 1,500 described 

species of insects and spiders. The Florissant Formation 

includes more known fossil butterflies than any other 

locality, as well as more than 140 plant species, and 

several species of fish, birds, and small mammals. 

Pleistocene fossils, such as mammoth bone, are also 

present in the monument. In addition a petrified forest of 

Eocene Sequoia- like stumps is preserved in tuffaceous 

mudstone, formed by a volcanic debris flow (lahar). 

The strata of the Florissant valley, deposited on the 

eroded surface of the 1.08- billion- year- old Pikes Peak 

Granite (Wobus, 2001), are primarily but not exclusively 

volcanic. They consist of lava flows, massive pumiceous 

tuffs, river gravels, agglomerates, and finely laminated 

fossiliferous paper shales. Although lacustrine shales 

form the most prominent outcrops, they constitute only 

a minor part (16%) of the total thickness of the 

formation. As emphasized by Evanoff and others (2001), 

instead of forming a single unit, the Florissant 

Formation—of which the fossiliferous lake beds are a 

part—comprises a complex and varied series of 

sediments and volcanics, which have been divided into 

six informal units. From oldest to youngest they are: (1) 

lower shale unit, (2) lower mudstone unit, (3) middle 

shale unit, (4) caprock conglomerate unit, (5) upper shale 

unit, and (6) upper pumice conglomerate unit. 
4 NPS Geologic Resources Division 

The Florissant Formation was deposited within a valley 

that was episodically blocked by lahar deposits that 

dammed the streams and formed Lake Florissant. As 

interpreted by Evanoff and others (2001), the Florissant 

Formation probably records two episodes of lake 

generation: the first represented by the lower shale unit; 

the second represented by the middle and upper shale 

units, which are divided by the caprock conglomerate 

throughout most of the monument. The two ages of lakes 

are separated by the lower mudstone unit, a fluvial 

deposit. Eventually the lacustrine deposits were buried 

by pumice gravel and lahars from the Thirtynine Mile 

volcanic field. 

Although some investigators concluded that complex 

faulting and subsequent erosion created the present 

outline of the lake beds, mapping of the Florissant 

Formation found no evidence of major faulting (Evanoff 

and Doi, 1992). Hence, the current interpretation 

contends that the exposure pattern reveals the extent of 

the ancient lake and that much of the present 

distribution of the Florissant Formation reflects the 

original area covered by paleovalley fill (Evanoff and 

others, 2001).

Eon Era Period Epoch Age (Ma) Age of 

Quaternary Holocene 0.01 

Pleistocene 1.81 

Neogene Pliocene 5.33 

Miocene 23.0 

Oligocene 33.9 

Eocene 55.8 

Cenozoic 

Paleogene 

Tertiary 

Paleocene 65.5 

Mammals 

Cretaceous 145.5 

Mesozoic Jurassic 199.6 

Triassic 251.0 

Reptiles 

Permian 299 

Pennsylvanian 318 

Carboniferous Mississippian 359.2 

Amphibians 

Devonian 416.0 

Silurian 443.7 Fish 

Ordovician 488.3 

Phanerozoic 

Paleozoic 

Cambrian 542.0 Invertebrates 

Proterozoic 2,500 

Archean 2,500–3,800? 

Hadean 

(Precambrian) 

3,800–4,600? 

Figure 1. Geologic Time Scale. Dates listed in the table are in millions of years (Ma) and reflect the International Union of Geological 

Sciences (IUGS) International Stratigraphic Commission (ICS) International Stratigraphic Chart (2003) at 

http://www.stratigraphy.org/chus.pdf. Exceptions include the boundary between Archean and Hadean, which the International Stratigraphic 

Commission does not list. However, the U.S. Geological Survey lists the boundary between Hadean and Archean at approximately 3,800 Ma 

and the formation of Earth at approximately 4,600 Ma, which are used here. Mississippian and Pennsylvanian are terms used primarily in 

North America, and Tertiary and Quaternary are no longer accepted by the International Commission on Stratigraphy (2003) but are included 

here because they are still in common use. 
FLFO Geologic Resource Evaluation Report 5 

Geologic Issues 

A GRE scoping session was held in Florissant Fossil Beds National Monument on October 

21, 1998, to discuss geologic resources, address the status of geologic mapping, and assess 

resource management issues and needs. The following section synthesizes the scoping 

results—in particular, those issues that may require attention from resource managers. 

Protection of Paleontological Resources 

The act establishing Florissant Fossil Beds national 

Monument was signed into law on August 20, 1969 

(Public Law 91- 60). In the statute, Congress underscored 

the importance of protecting “the excellently preserved 

insect and leaf fossils and related geologic sites and 

objects” at the monument. Congress also directed that 

the unit be managed in accordance with the National 

Park Service Organic Act. 

As required by the Organic Act of 1916, 16 U.S.C. §§ 1 et 

seq., and Management Policies 2001, the National Park 

Service strives to protect, preserve, and manage 

paleontological resources—including both organic and 

mineralized remains in body or trace form—for public 

education, interpretation, and scientific research. 

According to the Management Policies 2001, “the Service 

will study and manage paleontological resources in their 

paleoecological context (that is, in terms of the geologic 

data associated with a particular fossil that provides 

information about the ancient environment).” 

According to the “Scope of Collections Statement” for 

Florissant Fossil Beds National Monument, staff should 

be alert for confiscated archaeological and 

paleontological objects (National Park Service, 1998). 

These are objects recovered from unauthorized and 

illegal activities. They might include unearthed fossils, 

artifacts, eco- facts, and human remains illegally 

excavated or surface collected by unauthorized 

individuals within the monument boundaries. Museum 

personnel should be consulted as soon as possible to 

ensure proper handling and transportation of these 

materials. Such objects might be held temporarily as 

evidence if legal action is to be taken, but should be 

formally turned over to museum personnel as soon as 

possible. Once all legal questions are resolved, objects of 

particular significance from a known context will be 

added to the museum collection (Herb Meyer, Florissant 

Fossil Beds National Monument, written 

communication, May 2, 2005). 

Guidelines are in place at Florissant Fossil Beds National 

Monument for protecting and preserving the 

monuments fossils. The ability to manage and protect 

fossils is contingent upon an understanding of the 

occurrences and distributions of fossils, both geologic 

and geographic, and upon the factors threatening 

stability (Santucci and Koch, 2003) (table 1). 

For example, heavy cattle grazing in the late 1800s and 

early 1900s reduced plant cover and created sheet and 

gully erosion in what is now Florissant Fossil Beds 

National Monument (Florissant Fossil Beds National 

Monument, 1983c). Cutting of trees was also widespread 

(Herb Meyer, Florissant Fossil Beds National 

Monument, written communication, May 2, 2005). These 

examples show how human activities may initiate and 

accelerate erosion, which in turn may impact 

paleontological resources in the monument. 

In order to quantify loss, the National Park Service has 

established a system of measurable indicators of change 

to resource conditions (table 1). Paleontological localities 

vary widely in terms of rock types, fossil preservation, 

geomorphic characteristics, and human accessibility. 

Therefore, any specific indicator may not be useful or 

appropriate at all fossil sites. However, Santucci and 

Koch (2003) present an initial monitoring strategy for the 

National Park Service to assess or measure impacts to in 

situ paleontological resources. The new strategy is 

referred to as paleontological resource stability 

indicators (PRSI), as in the following list: 

Climatological Data Assessment PRSI 

This indicator allows the researcher to assess data on 

annual precipitation, rainfall intensity, relative humidity, 

wind speed, and freeze- thaw index (number of 24- hour 

periods per year when temperature fluctuates above and 

below 32°F [0°C]). 

Rates of Erosion Assessment PRSI 

This indicator allows the researcher to assess data on 

both inherent and dynamic factors such as specific rock 

characteristics, slope, soil loss, vegetation cover, and 

rates of denudation for fossiliferous rock units. 

Human Activity and Behavior Assessment PRSI 

This indicator allows the researcher to assess data on 

visitor use, visitor access routes and their proximity to 

fossil localities, documented cases of theft or vandalism, 

and commercial market values of fossils. 

Periodic Site Assessment PRSI 

This indicator allows the researched to assess data on the 

relative turnover rate of specimens at each fossil locality 

by monitoring the numbers of specimens destroyed or 

exposed at the surface. 

The use of these paleontological resource stability 

indicators provides a multidimensional approach to 

assessing the conditions of in situ fossils. Adoption of 

Servicewide protocols for monitoring these resources 

will further enable assessment of the threats and 
6 NPS Geologic Resources Division 

conditions affecting fossils throughout the National Park 

System (Santucci and Koch, 2003). 

Preservation of Fossil Stumps 

Fossilized redwood stumps that have been excavated are 

a primary park resource and the only paleontological 

resource that visitors can easily see in their natural 

setting. They are a major visitor attraction – about 95% of 

the monument’s 80,000 annual visitors view them. The 

stumps are located prominently along two short trails 

leading out from the visitor center: the closest stump is 

about 100 feet (30 m) down the trail and two others are 

about 150 feet (46 m) farther. The “Big Stump” is located 

about 0.25 mile (0.4 km) from the visitor center. 

Prior to the establishment of the monument, a number of 

petrified stumps were unearthed for commercial 

tourism. The unearthing (said to have included 

dynamite) exposed the stumps to harsh climatic 

conditions causing substantial deterioration. Park staff 

reburied some stumps in the late 1980s. However, 

because of the popularity of the stumps and their 

significance as an interpretive resource, reburial is not 

generally a preservation option. 

Park staff assume that temperature changes and moisture 

are responsible for the deterioration of the stumps. The 

stumps are only moderately silicified, and after repeated 

freezing and thawing, moisture infiltrating the porous 

cell structures results in spalling of the exterior. Due to 

the lesser degree of permineralization at Florissant, the 

fossil stumps have a higher porosity than most petrified 

wood, allowing for the absorption of low viscosity fluids 

As the stumps continue to weather, large chunks of 

petrified wood flake and fall from the trees, adding to an 

existing vandalism and theft problem. Continued 

exposure of the petrified stumps to the elements will 

result in their eventual disintegration by natural 

processes. The rate of deterioration is unknown, 

however, monument staff are developing an annual 

photo monitoring program to document deterioration 

(Florissant Fossil Beds National Monument, 1983c). 

Little is known about protecting such artifacts in situ, 

and no comprehensive conservation study of petrified 

wood has ever been conducted. However, because 

buildings are exposed to the same natural weathering 

processes as the tree trunks at Florissant, materials used 

for cultural conservation (e.g., historical building stones 

and gravestones) are being tested on petrified wood 

samples exposed to the elements at Florissant (figure 6). 

Other research involves an effort to understand the 

causes of deterioration, the geochemical properties of 

the petrified wood and the climatic impacts on the 

fossils. X- ray diffraction, x- ray fluorescence, and 

scanning electron microscopy can be used to study the 

mineralization process that the wood has undergone. 

This information will be compared to fossil wood 

samples from other localities. Results of this study will 

guide efforts to stabilize the in situ stumps (Jennifer 

Young, written communication, March 2, 2005). 

Other investigations have placed data- loggers into two 

stumps: one under the newly constructed shelters and 

one still exposed to the elements. These loggers will 

record temperature and relative humidity levels and are 

designed to fit into tight spaces. Investigators also placed 

a data- logger on top of both stumps. These microstations will record differences between surface 

conditions and internal conditions every three hours and 

log data for later analysis. These data will add to the 

documentation of the impact that fluids have on the 

samples by recording a year of weather conditions, to 

help determine which of the test materials best 

conserved the test samples under prevailing climatic 

conditions (Jennifer Young, Smithsonian Institute, 

written communication, March 2, 2005). 

When the testing of products is completed, conservation 

can take place in two phases. The first phase is the 

reconstruction of the trunks by reattaching some of the 

larger loose pieces using one or more adhesives.. The 

second phase is the prevention of further deterioration. 

Large fissures in the trunks require a filler material, while 

the finer cracks and pores require a less viscous fluid that 

will repel water (Jennifer Young, Smithsonian Institute, 

written communication, March 2, 2005). 

Estimates of Paleoelevation 

One of the significant aspects of the fossil flora at 

Florissant is its application in estimating past elevation 

(paleoelevation) during the Eocene Epoch. Indeed, few 

topics in the history of scientific research at Florissant 

have attracted as much published attention as 

paleoelevation (Meyer, 2001). The reason for this 

attention is that the results are important on many 

scientific fronts; the outcome will affect the work of 

paleobotanists, stratigraphers, climatologists, and 

structural geologists. 

Interpretations of the tectonic history and timing of 

uplift in the southern Rocky Mountains are based on the 

results of paleoelevation studies from Florissant. The 

Florissant Formation was deposited on the late Eocene 

erosion surface of the southern Rocky Mountains (see 

“Late Eocene Erosion Surface” in the “Geologic Features 

and Processes” section). For decades, geologists have 

used this erosion surface to reconstruct the erosional, 

tectonic, and climatic history of the southern Rocky 

Mountains. Marvine first recognized and reported the 

erosion surface in 1874. MacGinitie provided the first 

estimate of paleoelevation for Florissant in 1953. 

MacGinitie concluded, “the plant association indicates a 

region of moderate elevation, probably not more than 

3000 nor less than 1000 feet.” This estimate has been 

widely accepted and cited as evidence for significant 

uplift of the region during the late Tertiary (e.g., Epis and 

Chapin, 1975). 

The most commonly used method for determining 

paleoelevation from fossil floras uses estimates of mean 

annual temperature from isochronous sea- level and 

upland paleofloras in conjunction with terrestrial lapse 

rates (the rate at which temperature decreases with 
FLFO Geologic Resource Evaluation Report 7 

increasing elevation) (Axelrod, 1965; Axelrod and Bailey, 

1976). In other words, researchers calculate 

paleoelevation by using fossil plants to estimate two 

paleotemperatures: that at Florissant and that from 

another fossil flora of the same age and at the same 

latitude at sea level. By taking the difference in 

paleotemperature between sea level and Florissant, and 

multiplying that difference by the “appropriate lapse 

rate” of elevation change for 1°C, researchers can 

calculate estimates of paleoelevation. Reliable estimates 

of paleoelevation must include continentality 

(temperature variations between the coast and 

continental interior), paleogeography (latitudes of 

continents during the geologic past), and fluctuations in 

sea level. 

Considerable research on the paleoelevation at 

Florissant was done during the 1990s. One worker used 

paleoenthalpy (moist static energy in the atmosphere) for 

the purpose (table 2). Most estimates range from 6,235 

feet (1,900 m) to more than 13,450 feet (4,100 m); 

however, Axelrod (1998) estimates 1,495 feet (455 m). 

All the studies using various methodologies to estimate 

Florissant’s Eocene elevation suggest a much higher 

paleoelevation than that of MacGinitie (1953). The 

various methods for calculating paleoelevation are 

problematic, making estimated paleoelevations 

speculative. Nevertheless, they are a useful framework 

for comparison with other interpretations regarding late 

Eocene elevation in the southern Rocky Mountain 

region (Meyer, 2001). 

Development 

According to the U.S. Census Bureau, Colorado is the 

third- fastest growing state in the United States. 

Florissant Fossil Beds National Monument is located in 

Teller County which experienced a 64.9% increase in 

population between 1990 and 2000 making it the 10th 

fastest growing county in Colorado. 

In 1969, because of the threat of development and loss of 

paleontological resources, Congress set aside 5,992 acres 

(2,425 ha) of mountain meadows and forested, rolling 

hills as Florissant Fossil Beds National Monument. 

Today subdivisions surround the monument (Florissant 

Fossil Beds National Monument, 1983c), making it “a 

significant piece of protected, accessible, and interpreted 

open space in an increasingly developed mountain 

landscape” (Florissant Fossils Beds National Monument, 

draft comprehensive Interpretive Plan, July 30, 2004). 

Approximately 95% of the monument is classified as 

“natural zone,” incorporating, among other things, the 

ancient Lake Florissant and the undeveloped areas 

surrounding the lakebed. Approximately 11 acres (4.5 ha) 

or a fraction of 1% of the total acreage are classified as 

“historic zone,” including the Hornbek Homestead. The 

remaining 4% of the monument is classified as 

“developed zone,” which encompasses concentrated 

visitor and staff use areas, such as county roads, 

headquarters and visitor contact buildings, maintenance 

facilities, picnic area, residences, related parking areas, 

and utilities (Florissant Fossil Beds National Monument, 

1983a). 

Periodically, proposed development outside the 

boundary of the monument threatens the values held 

within: wildlife habitat, its undeveloped character, a 

place where plant and animal populations and 

communities are monitored for health, and a place where 

natural geologic processes such as erosion and 

groundwater movement are allowed to proceed 

unimpeded by human impact (Florissant Fossils Beds 

National Monument, draft comprehensive interpretive 

plan, July 30, 2004). For example, in 1986 the county 

planned to locate a landfill adjacent to the northwest 

corner of the monument. This action would have had 

serious aesthetic and environmental consequences for 

the monument (McChristal, 1994). Superintendent Tom 

Wylie (1985–1988) announced that the National Park 

Service had filed suit in state court to block approval of 

the dump site. This pressure caused the contractor to 

withdraw his proposal (Colorado Springs Sun, February 

12, 1986; Colorado Springs Gazette Telegraph, February 11, 

1986). 

The natural resource management plan (1983) for the 

monument addresses impacts to natural resources from 

rapid expansion of subdivisions adjacent to the 

monument and the anticipated increase in visitor use, by 

stating that “the monument will maintain a boundary 

fence to discourage adverse use of monument 

properties.” Protection is required for key resources, 

which were significant in the establishment of the 

monument, that is, the paleontological resources. These 

resources are very fragile and subject to impacts of 

development especially when excavation is necessary. 

Realizing the fragile nature of these resources as well as 

the need to provide adequate facilities to meet visitor and 

administrative needs, investigators conducted a 

stratigraphic survey to define the location of the various 

paleontological layers and significant geological 

conditions (Florissant Fossil Beds National Monument, 

1983a). Upon identifying the potential developable sites, 

soil borings were taken to determine the depth and 

condition of soils. These data were one of the primary 

factors in developing the alternatives identified in the 

environmental assessment for the general management 

plan development concepts (1983). 

Buried Stumps 

Of primary concern for development within Florissant 

Fossil Beds National Monument is the discovery of as yet 

unknown buried stumps. Knowledge of their locations 

and distributions will give planners a guide for the 

suitability and appropriateness of future development 

locations, and will aid paleobotanists to more accurately 

describe Florissant paleoenvironments (Florissant Fossil 

Beds National Monument, 1983b). Construction of 

building and shelter foundations, underground utilities, a 

water tank, and a septic leach field will require 

excavation into the soils and bedrock to depths ranging 

from 4 to 16 feet (1.2 to 4.9 m) (Chen Northern, Inc., 

unpublished geotechnical engineering report, job no. 1 

562 90, October 17, 1990). Excavation in the soils, 
8 NPS Geologic Resources Division 

consisting of clay, clayey to silty sand, and clayey gravel 

can probably be accomplished with conventional earth 

excavating equipment. Construction of buildings often 

requires excavating into the rocks of the Florissant 

Formation, not just the soil (Herb Meyer, Florissant 

Fossil Beds National Monument, written 

communication, May 2, 2005). 

Excavation in the underlying bedrock, consisting of shale 

units (sandstone, siltstone, and claystone), will likely 

require heavy duty earth excavating equipment. Difficult 

excavation conditions could occur if cemented zones are 

encountered in the rock. Pneumatic chisels, ripping or 

blasting may be required, particularly in confined 

excavations such as trenches. Consideration should be 

given to the use of heavy duty trenching machines for 

utility trench excavations, and possibly building 

foundations (Chen Northern, Inc., unpublished 

geotechnical engineering report, job no. 1 562 90, 

October 17, 1990). 

Most petrified stumps or logs within 1 or 2 feet (0.3 or 0.6 

m) of the surface can be readily located by high 

concentrations of petrified wood fragments at the 

surface. Stumps more deeply buried are not so easily 

detected. For this reason, investigators have periodically 

pursued the question of how best to locate more deeply 

buried stumps by remote detection (Florissant Fossil 

Beds National Monument, 1983b). 

According to the 1983 report, Stratigraphic Surveys for 

Site Selection of Visitor and Administrative Facilities, of all 

the geophysical methods examined at the time, 

investigators considered the electrical conductivity 

method the most feasible; they also studied seismic, 

ground magnetometer, gravity, and electrical resistivity. 

This preferred technique depends upon the electrical 

conductivity of earth materials, which is directly 

proportional to the amount of underground moisture. A 

conductivity meter, mounted on a 15- foot (4.6- m) long 

boom, broadcasts and receives RF radio frequencies of 

9.8 KHz, which can measure ground conductivity up to 

30 feet (9 m) in depth under optimum soil moisture 

conditions. An abrupt change in ground conductivity is 

an indicator of a buried petrified stump. The instrument 

and boom are carried by hand across the ground, with 

sampling transects approximately 10 feet (3 m) wide, and 

readings taken every 5 feet (1.5 m) along the transect. The 

technique is totally nondestructive, and is estimated to 

take approximately 20 hours for a 3- to- 4- person crew 

to survey 1 acre (0.4 ha). Although this type of survey may 

not be able to detect stumps of less than 15 feet (4.6 m) in 

diameter, the ease and rapidity of sampling makes it the 

most feasible of all the geophysical methods that have 

been examined to date (Florissant Fossil Beds National 

Monument, 1983b). 

Groundwater 

Groundwater level and quality will also be impacted by 

development. Groundwater feeds seeps and springs, 

which are generally areas of high biodiversity. An 

undetermined number of springs occur in the 

monument. The quality and quantity of these springs—

and the quality of the two major perennial streams—are 

unknown (Florissant Fossil Beds National Monument, 

1983c). Groundwater level is significant for management 

because a decrease in groundwater level could have a 

direct effect on the monument’s resources, in particular, 

seeps and springs and the plants and animals that depend 

on this source of water. Quantifying groundwater level is 

important because park managers could use this 

information for planning and future decision making 

related to development outside the monument’s 

boundary. 

According to the monument’s natural resource 

management plan and environmental assessment (1983), 

the monument contains only a portion of land within the 

watershed. All surrounding subdivisions have individual 

septic tanks and no sewer systems, and all have 

individual wells within the aquifer. The primary land 

uses outside the monument are for residential dwellings 

and livestock. A potential for contamination of 

monument waters from outside sources exists (Florissant 

Fossil Beds National Monument, 1983c). 

Two major wells within the monument provide water for 

human consumption. One well, located adjacent to the 

visitor center, is 165 feet (50 m) deep and capable of 

pumping an estimated 4–6 gallons (15–23 L) per minute 

into a 50 gallon (189 L) pressure tank. Water quality is 

poor because of high mineral content, but treatment 

using filters and chlorination makes it potable (Florissant 

Fossil Beds National Monument, 1983c). 

A second well is located near a residence in park housing 

at the eastern edge of the monument. This well is 60 feet 

(18 m) deep and is capable of producing an estimated 0.5–

1 gallon (2–4 L) per minute. This water also has a high 

mineral content and is used for sanitation purposes only 

(Florissant Fossil Beds National Monument, 1983c). 

Other abandoned wells are known to be in the 

monument but their numbers, locations and quality and 

quantity of water is not known (Florissant Fossil Beds 

National Monument, 1983c). 

With many unknowns, a need exists to inventory, assess, 

and monitor the water resources of the monument. In 

addition, a water resources management plan is needed 

(Florissant Fossil Beds National Monument, 1983c). 

Dam Removal and Stream Restoration 

A number of small intermittent spring- fed streams flow 

through Florissant Fossil Beds National Monument and 

into Grape Creek. Many dry gulches also exist. In the 

1930s and 1940s, ranchers and farmers constructed 44 

earthen dams in many of these drainages. These dams 

were intended to provide erosion control and facilitate 

water retention and diversion for agriculture. It has been 

National Park Service policy to restore native 

communities and natural processes. 

Since the earthen dams interrupted natural drainage and 

altered natural hydrologic and geomorphic processes in 
FLFO Geologic Resource Evaluation Report 9 

the monument, they did not comply with National Park 

Service policy. The earthen dams posed an ongoing 

threat to the natural landscape of Florissant by: 1) 

inhibiting natural processes and scenic beauty; 2) altering 

the natural occurrence and function of wetlands, 

floodplains, and riparian areas; 3) raising concern for 

sedimentation to downstream wetlands; and 4) creating a 

potential flood hazard. A breach or failure of one or 

more of the dams and the resultant flooding, accelerated 

erosion, and increased sedimentation of downstream 

wetlands made the structures a threat to the natural 

resources of Florissant. In the event of heavy rainfall, the 

earthen dams would likely fail because of their small sizes 

and lack of structural integrity. 

In 1997 all 44 earthen dams were inventoried and 

evaluated by ranking the removal of each earthen dam 

based on effects on wetlands, hydrologic alteration, size, 

vegetation alteration, accessibility to equipment, erosion 

concerns (past, present, and predicted), use as a wildlife 

resource and critical habitat, aesthetics, and other 

potential benefits such as flood control and water 

sources for fire suppression (Birchfield, 2000). The dams 

that were recommended for removal had the fewest 

benefits, greatest impacts, and greatest likelihood of 

restoration success (Florissant Fossil Beds National 

Monument, 2001) (IT Corporation, 2001a). 

During the course of the Boulder Creek reclamation and 

restoration, five dams were removed and re- vegetated 

and one culvert (Structure 33) was replaced (figure 4). 

Approximately 15,454 cubic yards (11,814 m3

) of material 

was moved from the former dam structures and placed in 

fill areas to blend inconspicuously into the surrounding 

topography (table 3). After reclamation, the areas 

disturbed by the dam removal—approximately 4.5 acres 

(1.8 ha) of land: 2 acres (0.8 ha) of wetlands and 2.5 acres 

(1.0 ha) of dry uplands—were seeded or re- vegetated. 

Success of the re- vegetation effort will not be 

immediately evident. The National Park Service will need 

to conduct monitoring to detect any potential problems 

and to evaluate the effectiveness of the reclamation 

efforts. 

On October 19, 2001, staff members from the National 

Park Service, the U.S. Army Corps of Engineers, and IT 

Corporation conducted a final walk- through after which 

National Park Service representatives accepted the work 

as complete. However, on October 30, 2001, the National 

Park Service notified IT Corporation and U.S. Army 

Corps of Engineers that the straw crimping was 

insufficient and had to be redone because much of the 

straw had blown away from the upland slopes during 

high winds. Additional straw was placed and hand 

crimped during the week of October 29, but high winds 

continued to dislodge the straw. The National Park 

Service requested additional erosional control mats for 

the most exposed areas. These mats were installed during 

the weeks of October 29 and November 5, 2001 (IT 

Corporation, 2001b). 

Agricultural Terraces 

In the 1930s, the Civilian Conservation Corps (CCC) built 

terraces to irrigate potatoes, and perhaps lettuce, fields 

(figure 3). Farmers harvested the last potato crop from 

the monument property in the 1970s (Beth Simmons, 

written communication, May 23, 2005). The terraces 

were also meant to mediate the flow of water on the 

landscape in order to prevent soil erosion during the 

drought of the 1930s. At the time, governmental incentive 

programs for farmers required terracing. Farmers would 

not receive loans or futures if they did not cooperate 

with “contour” or “strip” farming. 

The terraces disturbed the natural flow of water by 

trapping and holding water at higher than natural water 

levels (in order to water potatoes). Natural conditions 

would have been lower (to feed beaver ponds). The 

terraces redirected flowing water after rainstorms, 

potentially creating a zone of unnatural saturation. 

Abandoned Mine Land Site 

An abandoned mine land (AML) site was located south 

of the Florissant Cemetery just inside the north 

boundary of the monument along Upper Twin Rock 

Road. The adit was cut into decomposed Pikes Peak 

Granite and had no apparent mineralization. The site 

was reclaimed in August 2000 by backfilling with native 

rock followed by waste rock and soil. No other AML 

sites are known in the park. 

Mining 

As in most units of the National Park System, federal 

mineral leasing and the location of mining claims are 

prohibited inside the monument. The monument is not 

known to contain any privately owned mineral rights and 

less than 6 acres of the park are non- federally owned. 

While some limited mining occurred inside the 

monument prior to its inclusion in the National Park 

System, no mining occurs today. 

The Cripple Creek mining district, 15 miles (24 km) 

southeast of Florissant, is the richest gold producing area 

in Colorado with more than 21,000,000 troy ounces 

produced (Davis and Streufert, 1990). Gold mining 

continues in Cripple Creek today. 

In their report, Rogers and Alberts refer to “lava flows 

associated with the lake beds at certain points” that jut 

out as promontories “into the lake on either side.” 

Scudder (1883) called these flows “trachyte”—finegrained, generally porphyritic, extrusive igneous rock, 

usually containing biotite, hornblende, and pyroxene. 

According to Rogers and Alberts, many of these trachytic 

exposures still bear marks of prospecting from miners 

during the Cripple Creek boom. Lakes (1899), mentions 

that “every bed of tuff and breccia” was tunneled and 

prospected for gold, without profit. Optimism for 

another “Cripple Creek” in the Thirtynine Mile volcanics 

was so high that the town of Freshwater (now Guffey) 

was platted, but the bonanza never occurred (Evanoff, 

1994). 
10 NPS Geologic Resources Division 

Potential Research 

Eruptive Source of Pumice and Ash 

The eruptive source of the pumice and ash in the 

Florissant Formation is unknown. This is a significant 

piece of missing information for interpreting the geologic 

story at Florissant Fossil Beds National Monument. 

Geologists and park interpreters would like to know 

more precisely the source and age of the volcanic ash in 

which Florissant fossils are found (Florissant Fossil Beds 

National Monument, draft comprehensive interpretive 

plan, July 30, 2004). 

Evanoff and others (2001) briefly address possible 

sources for the Florissant ash and pumice and identify 

three possible sources: (1) early, pre- ignimbrite 

eruptions from the 33.8- million- year- old (Ma) Mount 

Aetna caldera, (2) late, post- ignimbrite eruptions from 

the 34.3- Ma Grizzly Peak caldera, or (3) eruption of local 

rhyolite dome in the vicinity of Florissant (figure 5). The 

Guffey volcanic center is another possible source of 

volcanic material (Herb Meyer, Florissant Fossil Beds 

National Monument, written communication, May 2, 

2005). 

The suitability of these possibilities as the source of 

Florissant ash and pumice is questionable, however. 

First, sanidine—used in 40Ar/39Ar age dating—from the 

Antero Tuff (erupted from the Mount Aetna caldera) has 

a measurably younger age than the Florissant Formation, 

and significantly higher K/Ca ratios (68.1 ± 16.4 Ma) 

(McIntosh, unpublished data, 2001)—calculated from Kderived 39Ar and Ca- derived 37Ar. Second, investigators 

have not identified any outflow ignimbrites from the 

Grizzly Peak caldera, and sanidine samples of ignimbrites 

from the Grizzly Peak intracaldera are older than the 

Florissant Formation sanidine, and also have higher 

K/Ca ratios (84.4 ± 6.2 Ma) (McIntosh, unpublished data, 

2001). Third, geologic mapping in the Florissant area has 

not identified any rhyolitic dome in the appropriate 34-

million- year- old age range, though investigators suggest 

that such domes may have been present but are now 

eroded or covered (Evanoff and others, 2001). 

In an attempt to determine the eruptive source, one 

possible way is to study the Florissant Formation in the 

field and analyze samples in the laboratory to develop a 

detailed microstratigraphic framework. This would help 

determine the source(s) for the volcanic sediments of the 

Florissant Formation by analyzing trace elements that 

can “fingerprint” the various ash layers within the 

Florissant Formation. New radiometric dates will better 

resolve the age and duration of the Florissant Formation. 

Eocene-Oligocene Climate Change and Fossil Resources 

Florissant Fossil Beds National Monument contains the 

world’s most significant upland fossil deposit during the 

Eocene- Oligocene transition (see figure 1). This time 

interval, immediately preceding a global cooling event, is 

the most pronounced climate change of the Paleogene 

Period (see figure 1). In order to determine paleoclimatic 

parameters such as mean annual temperature and mean 

annual precipitation, park managers have proposed 

collecting fossil leaf assemblages from several 

stratigraphic levels at different sites around the Eocene 

Florissant lake basin. This will provide new evidence to 

interpret the small- scale variability of biotic 

communities and microclimatic conditions around the 

lake basin in time and space. A comparison of Florissant 

fossils with the fossil plants from other localities, such as 

the John Day basin, will provide an ideal basis for 

studying the impacts and nature of climate change over a 

wide geographic area. 

Active paleontological research at Florissant Fossil Beds 

National Monument provides a means for educating 

visitors about fossil resources and demonstrating what 

fossils can reveal about climates and ecosystems of the 

past. Additional fossil specimens will enhance the 

monument’s existing, small collection and ensure that 

park staff will be able to construct new exhibits that do 

not rely solely on long- term loans from other museums. 

Most of the existing collections of Florissant fossils were 

made and studied by non- National Park Service workers 

long before the establishment of the monument. Many of 

these collections are housed at other museums, including 

the University of California at Berkeley, the University of 

Colorado, the National Museum of Natural History 

(Smithsonian), and Yale University. Unfortunately, few 

early collectors noted important aspects of stratigraphic 

position or even precise locality information severely 

limiting the utility of these collections in discerning 

patterns of biotic change though time and space around 

the Eocene lake basin at Florissant. It is important to 

collect new paleobotanical specimens from the field in 

order to form a more accurate basis for comparison with 

the fossils from John Day and other fossil localities from 

western North America. This will also result in large 

collections of fossil insects that will be of use in new 

exhibits and available for related research. 
FLFO Geologic Resource Evaluation Report 11 

Table 1. Factors that Affect the Stability of In Situ Paleontological Resources 

SURFACE 

Physical 

Tectonics 

• seismicity 

• folding/faulting 

• extrusive events (lava 

flows) 

Weathering/Erosion 

• solar radiation 

• freeze/thaw 

• wind 

• water 

• fire 

• gravity 

• mass wasting 

• abrasion during transport 

Chemical 

• surface water 

• soil/rock pH 

• mineral replacement 

• oxidation (rust, 

pyritization) 

Biological 

Displacement 

• pack rats 

• harvester ants 

Destruction/Damage 

• burrowing organisms 

• trampling ungulates 

• vegetation (root and 

lichen growth) 

Human 

• construction (buildings, 

roads, dams) 

• mining 

• military activities 

(construction, vehicles, 

ballistics) 

• theft/vandalism 

• poor science and recovery 

techniques 

• livestock 

• agriculture 

• recreational activities 

(offroad vehicle travel) 

SUBSURFACE 

Physical 

Tectonics 

• seismicity 

• folding/faulting 

• intrusive events 

• metamorphism 

Weathering/Erosion 

• freeze/thaw (permafrost) 

• water movement (piping, 

cavern formation) 

• gravity 

• mass wasting 

• compaction 

• rock falls 

Chemical 

• groundwater 

• soil/rock pH 

• mineral replacement 

• metamorphism (partial 

melt, recrystallization) 

Biological 

Displacement 

• root growth 

• bioturbation 

Destruction/Damage 

• burrowing organisms 

• root growth 

Human 

• construction (buildings, 

roads, dams) 

• mining 

• military activities 

(construction, ballistics) 

• theft/vandalism 

• poor science and 

excavation technique 

(dynamite) 

Source: Santucci and Koch (2003). 
12 NPS Geologic Resources Division 

Table 2. Estimates of Florissant Paleoelevation 

Year Investigators Estimate 

1953 MacGinitie 1,000–3,000 ft (305–915 

m) 

1986, 

1992 

Meyer 8,040 ft (2,450 m) 

Range: 6,230–7,550 ft 

(1,900–2,300 m) 

1992 Wolfe 8,860–9,515 ft (2,700–

2,900 m) 

1992 Gregory and 

Chase 

7,550–10,500 ft (2,300 m 

± 400 m–3,200 ± 800 m) 

1994 (a 

and b) 

Wolfe 13,560 ft (4,133 m) and 

7,400 ft (2,255 m) 

1994 Gregory 7,550–10,830 ft (2,300 ± 

370 m–3,300 ± 750 m) 

1995 Forest et al. 9,515 ft (2,900 ± 670 m) 

1996 Gregory and 

McIntosh 

6,235–10,170 ft (1,900 ± 

500 m–3,100 ± 800 m) 

1997 Axelrod 1,495 ft (455 m) 

1998 Wolfe et al. 12,470 ft (3,800 ± 800 m) 

Table3. Structure Cut and Fill Volumes 

Structure Location Approximate 

Volume of Soil in 

cubic yards (m3

) 

47 Boulder Creek, 

midstream (dry) 

59 (45) 

32 Boulder Creek, 

upstream (dry) 

1,010 (772) 

31 Boulder Creek, 

upstream (pond) 

1,680 (1,284) 

33 Culvert along path 

over Boulder Creek 

0 

9 Southernmost, along 

Route 1 (dry) 

10,095 (7,718) 

14 

Easternmost, across 

from visitor center, 

along Route 1 (pond) 

2,610 (1,995) 

Total 15,454 (11,814) 

Source: IT Corporation (2001b). 
FLFO Geologic Resource Evaluation Report 13 

Figure 2. Abandoned Mine Land Site. Reclamation of a small adit prospect in Florissant Fossil Beds National Monument occurred on August 

3, 2003. Staff of the National Park Service Geologic Resources Division and volunteers from the San Juan County Youth Corps completed 

the work. National Park Service photo by John Burghardt. 
14 NPS Geologic Resources Division 

Figure 3. Agricultural Terrace West of Hornbeck Homestead. The Civilian Conservation Corps (CCC) built the terraces in order to irrigate 

agricultural fields. The terraces were also meant to mediate the flow of water on the landscape to prevent soil erosion during the drought of 

the 1930s. However, they disrupt natural flow after rainfall events. National Park Service photo. 
FLFO Geologic Resource Evaluation Report 15 

Figure 4. Dam Removal and Stream Restoration. In 2001, Structure 32, a dam on Boulder Creek, was removed along with other structures 

during a dam removal and stream reclamation project in Florissant Fossil Beds National Monument. The IT Corporation, a contractor of the 

U.S. Army Corps of Engineers Rapid Restoration Group, conducted the work. National Park Service photos by Hal Pranger. 
16 NPS Geologic Resources Division 

Figure 5. Regional Map of Central Colorado. Investigators have suggested three possible sources of the pumice and ash in the Florissant 

Formation: Mount Aetna caldera, Grizzly Peak caldera, and a local rhyolite dome in the vicinity of Florissant. The Guffey volcano complex is 

another possible eruptive source. Source: Evanoff and others (2001). 

Figure 6. Preservation of Fossil Stumps. The excavated, fossilized Sequoia-like stumps are a primary park resource and the only in situ 

paleontological resource that can be seen easily by visitors in their natural setting. For these reasons, they cannot be buried for protection; 

however, a scientist from the Smithsonian Institute is investigating materials used in cultural conservation to potentially protect these 

resources against further deterioration. Photo by Katie KellerLynn. 
FLFO Geologic Resource Evaluation Report 17 

Geologic Features and Processes 

This section provides descriptions of the most prominent and distinctive geologic features 

and processes in Florissant Fossil Beds National Monument. 

Evolution and Global Climate Change 

Because of its world- renowned reputation for fossils as 

part of an ancient ecosystem, Florissant Fossil Beds 

National Monument plays an important role in the 

present- day debate about evolution. Florissant provides 

evidence that organisms and ecosystems evolve, and that 

different groups of organisms such as plants and 

mammals—and different type of organs, such as leaves 

and flowers—have evolved at difference rates (Meyer, 

2003). 

Most of the fossil plants and many of the fossil insects at 

Florissant can be placed into modern genera. On the 

other hand, the few fossil mammals from Florissant all 

represent extinct genera, and in the case of the 

brontotheres and the oreodont, extinct families. 

About 280 genera of insects and spiders found at 

Florissant Fossil Beds National Monument have been 

described as extinct. Several plant genera are also extinct 

including the two most abundant plants at Florissant, 

Cedrelospermum and Fagopsis, extinct members of the 

elm and beech families (Meyer, 2003) However, most of 

the fossil plants and insects represent genera that still live 

today. However, many of their modern distributions do 

not overlap. These genera that once lived side by side in 

the late Eocene forest at Florissant are represented by 

related living species now restricted to widely separated 

parts of the world (Meyer, 2003). Florissant’s ancient 

community includes organisms whose modern relatives 

occupy not only different regions, but also different 

climatic habitats (Boyle, 2004; Meyer, 2003). Nowhere in 

the modern world is the same association of plants and 

insects found living together. Among the fossils at 

Florissant, plants and insects that today are subtropical 

are juxtaposed beside others that are typically cooltemperate in modern distribution (Meyer and Weber, 

1995). 

Although the ancient Florissant community shows just 

one snapshot in a long sequence of ecosystem evolution 

(Meyer, 2003), the data it furnishes has contributed to 

national debates on evolution and global climate change, 

which are in need of salient information. Because 

Florissant was an ancient upland ecosystem that existed 

immediately preceding a very significant cooling of the 

world’s climate, the clues it preserves in the rock record 

provide important insights for understanding of the 

evolution of North American biotic communities and 

their response to climate change. 

Late Eocene Erosion Surface 

The high meadow in which Florissant Fossil Beds 

National Monument lies has caught the attention of 

geologists and visitors alike. Geologists interpret this 

feature as the remains of an extensive erosion surface 

developed by stable rivers, and visitors wonder that such 

moderate relief is possible at 8,200 feet (2,500 m). Since 

this erosion surface was first recognized and reported 

(Marvine, 1874), it has been controversial. Bradley (1987) 

makes three pertinent points about the erosion surfaces 

in the Front Range: (1) they are cut chiefly on 

Precambrian granitic and metamorphic rocks, (2) they 

can be no older than Tertiary because they are carved 

into rocks deformed during the Laramide Orogeny, and 

(3) they show a broad relationship to crystalline 

lithology. The surfaces are flattest and most extensive in 

those areas where granitic rocks are most abundant as in 

a southern area around Pikes Peak in Pikes Peak Granite 

(about 1.08 billion years old), and in a northern area that 

extends onto the Laramie Range in Sherman Granite and 

associated intrusives (all approximately 1.4 billion years 

old). Between these two areas, metamorphic rocks are 

relatively more abundant and the erosion surfaces have 

greater local relief. 

Basic questions about the erosion surfaces remain 

regarding (1) the number of surfaces—investigators have 

recognized as few as one to as many as 11 surfaces; (2) the 

age—early or late Tertiary, that is 20 million or 50 million 

years old; and (3) the genesis—peneplain (forming at low 

elevations and with low river gradients) vs. pediment 

(forming under arid conditions along mountain fronts or 

plateaus). 

The most recent interpretation regarding the number 

and ages of erosion surfaces identifies one major 

subsummit (lower, older [late Eocene]) surface, 

including the surface at Florissant, and a second (higher, 

younger [late Tertiary]) summit surface, for example, the 

smoothly rolling tundra surface in Rocky Mountain 

National Park. Although most workers agree that the 

higher erosion surface has been affected by Quaternary 

periglacial activities, the question of genesis—

peneplanation vs. pedimentation—remains largely 

unresolved (Bradley, 1987). The higher surface is much 

less extensive than the lower subsummit surface. Studies 

have concentrated on the lower erosion surface that has 

been called “Rocky Mountain,” “Sherman,” “Late 

Eocene,” and “Subsummit,” which leaves the full 

significance of the higher surface, which has been called 

“Flattop” and “Summit,” inconclusive (Bradley, 1987). 

Because peneplains were believed to form at low 

elevations and with low river gradients, substantial uplift 

was required to bring them to their present elevations. 

Using this kind of evidence, investigators estimated late 

Cenozoic uplift to be between 5,000 and 9,000 feet (1,524 

and 2,743 m) (Davis, 1911; Chamberlain, 1919). However, 

reclassifying peneplains as pediments greatly reduced the 

amount of uplift required (Johnson, 1931, 1932; Mackin, 
18 NPS Geologic Resources Division 

1947). Uplift was then estimated from displaced flora and 

fauna, for example using fossils from Florissant, 

Colorado (Epis and Chapin, 1975). In the 1980s, the 

outcome seemed ironic, that is, magnitude of uplift based 

on paleontology is approximately the same as it was 

when based on peneplains (Bradley, 1987). During the 

1990s, however, investigators developed new methods 

that used estimates of paleoclimate and lapse rates—the 

rate at which temperature decreases with increasing 

elevation—to measure paleoelevation (methodologies 

summarized in Meyer, 2001). Another method uses 

principles of atmospheric energy conservation to 

determine paleoelevation from estimates of 

paleoenthalpy—a thermodynamic property (heat 

content) of the atmosphere, which can be estimated from 

fossil plants. Using these methods, investigators 

consistently concluded that during the Eocene Florissant 

was as high as today, or perhaps even higher (Meyer, 

2003). Nevertheless, depending on the method used, 

current estimates cover a broad range—from much lower 

than today to much higher than today. Hence, the debate 

about Florissant’s elevation 34 million years ago 

continues. 

Geologists have studied erosion surfaces so extensively 

because of the implications for reconstructing the 

erosional, tectonic (uplift), and climatic history of the 

Rocky Mountain region. For decades geologists have 

used erosion surfaces as clues to the post- Laramide 

deformational history of the middle and southern Rocky 

Mountains. The outcome has at least three significant 

implications: (1) Did global climate change or did uplift 

influence the sharp contrast between ancient and 

modern ecosystems at Florissant? (2) When did most of 

the uplift of the southern Rocky Mountains occur, 

before the late Eocene during the Laramide Orogeny, or 

as post- Laramide deformation? and (3) Can regional 

erosion surfaces form at high elevations? Additional 

questions ponder the erosional history of the surfaces: 

How much has the lower erosion surface been lowered 

since the late Eocene? And, how much lowering of the 

late Eocene surface is permissible for it still to be called 

the late Eocene surface, and beyond which it should be 

called a younger surface? 

The Florissant area remains part of this continued 

controversy. For example, Divide, Colorado, is situated 

on a prominent erosion surface, which rises to the south 

and southeast of the town and extends to the north and 

east onto the Rampart Range. Investigators have 

considered this surface to be an exhumed part of the late 

Eocene surface (Epis and Chapin, 1975; Scott and Taylor, 

1986). However, a few features related to this surface cast 

some doubt on this interpretation: no outcrops of the 

Wall Mountain Tuff occur on this surface, and the oldest 

deposits on this surface are the gravels at Divide, which 

contain clasts derived from the Cripple Creek volcanic 

field (Epis and Taylor, 1975; Epis and others, 1980). The 

gravels at Divide on this surface and the truncation of the 

Wall Mountain outcrops east of Florissant suggest that 

this surface is not a simple exhumed surface of late 

Eocene age. The modern low- level surface probably 

acquired its present form in the Miocene (Evanoff, 1994). 

If the Rampart- Divide surface is an exhumed late 

Eocene surface, then erosion must have removed all of 

the exposures of Wall Mountain Tuff without 

significantly eroding the Proterozoic crystalline rocks. 

Another interpretation is that this surface developed 

over a longer period of time, from exposure of 

Proterozoic rocks in the Paleocene until the Miocene, 

when the Divide drainage was graded to the Ogallala 

Formation of eastern Colorado. This second 

interpretation implies that the granite continued to be 

eroded between the late Eocene and Miocene, and that 

the elevation difference between Florissant and the 

Divide area may have been greater in the late Eocene 

than it is today (Evanoff, 1994). 

Paleontological Resources 

The incredible fossil record at Florissant, which consists 

of organisms that are not ordinarily fossilized, has 

enabled paleontologists and geologists to reconstruct a 

relatively brief moment of time at the end of the Eocene 

Epoch (about 34 million years ago). The fossils at 

Florissant are of five types: 

1. Plants—redwood stumps; palynomorphs (pollen and 

spores); leaves, fruits, seeds, and flowers 

2. Diatom mats (see “Sedimentation and Fossilization” 

section) 

3. Spiders, insects, and myriapods (multi- legged 

arthropods) 

4. Mollusks (clams and snails) and ostracods 

(microscopic crustaceans) 

5. Vertebrates—fish, birds, and mammals 

In 2003 the Smithsonian Institute published Fossil of 

Florissant by Herbert W. Meyer. This book includes a 

complete listing of the fossil organisms from Florissant 

and descriptions of the five types of fossils. In addition, 

the monument’s Web site hosts a fossil database that 

brings together collections that are now in at least 17 

different museums throughout North America and 

Europe. This database integrates taxonomic, museum 

collection, and publication data into a single virtual 

museum. It includes new photographs for almost all of 

the published Florissant specimens. Three different 

portals accommodate users: scientific researchers, 

educators and students, and the layperson. 

Since publishing Fossils of Florissant, investigation has 

revealed additional information about fossil mammals at 

Florissant (Worley, 2004). Hence, this information is 

provided in some detail in this report. Other fossils are 

discussed generally in order to highlight the types of 

paleontological resources at Florissant Fossil Beds 

National Monument. However, readers of this report are 

encouraged to consult Fossils of Florissant for a thorough 

summary and descriptions of fossil resources, which is 

beyond the scope of this report. 
FLFO Geologic Resource Evaluation Report 19 

Fossil Plants 

From giant redwood stumps to microscopic pollen 

grains, plant fossils include leaves, fruits, seeds, cones, 

and flowers from about 140 species. Angiosperms 

(flowering plants) dominate the flora, but conifers are 

also conspicuous (e.g., yews, Cyprus, and pine). Families 

of flowering plants include: birthwort, laurel, barberry, 

sycamore, beech, birch, walnut, storax, willow, 

basswood, cocoa, elm, spurge, currant, rose, evening 

primrose, legumes, bladdernut, maple, citrus, 

tree of heaven, torchwood, cashew, spindle tree, 

buckthorn, grape, hydrangea, hard- rubber tree, ginseng, 

elder, honeysuckle, sweetsop, morning glory, olive, 

greenbrier, yam, sedge, grass, palm, and cattail. 

More than 50 families are represented by fossil pollen at 

Florissant, possibly including the world’s earliest known 

record of the sunflower family, which is today the largest 

family of flowering plants (Meyer and Weber, 1995). 

Most of the leaf and fruit fossils come from trees and 

shrubs, and only rarely are the small herbaceous plants 

represented. In some instances the leaf cuticle is 

preserved, showing details of the outermost layer of the 

leaf’s cells. 

Fossil Stumps 

The petrified forest is one of the main attractions at 

Florissant Fossil Beds National Monument. Using their 

remains as indicators, these trees must have been 

spectacular when they were living—forming a grove 

along the valley bottom with a forest canopy at least 197 

feet (60 m) high (Meyer, 2003). For example, the Big 

Stump measures 12 feet (3.7 m) tall, 38 feet (12 m) around, 

and may have been greater than 230 feet (70 m) tall when 

the mudflow buried the base of the 750- year- old tree 

(Florissant Fossil Beds National Monument, Petrified 

Forest Walk). 

The ancient redwoods formed a forest that bordered the 

old drainage of the Florissant valley. During the late 

Eocene a single mudflow from the Guffey volcano 

covered the forest floor with 16 feet (5 m) of volcanic 

mud. Although modern coast redwoods are known to 

survive partial burial by sprouting new roots at a higher 

level (Helley and LaMarche, 1968), investigators have 

observed no such features in the exposed trunks at 

Florissant (Gregory- Wodzicki, 2001). Therefore, the 

trees were probably killed by the mudflow and died 

when the roots could no longer receive sufficient 

oxygen. Even though the trees died because of this event, 

the mudflow also helped preserve their remains for 34 

million years. Geologic processes, a combination of 

mudflows, silica- rich groundwater flow, and 

permineralization, preserved the stumps. Stumps are 

preserved within the lower mudstone unit of the 

Florissant Formation. Mapping of 31 stumps at Florissant 

revealed that they occur in a single plane, and 91% of 

them are vertical (Evanoff and Doi, 1992). Hence, the 

stumps represent a single in situ forest where the trees 

were encased while in a rooted position, and not 

transported to their current location by the mudflow. 

Unfortunately, the stump locations reveal little about the 

late Eocene forest spacing because the area has been 

heavily collected. A. C. Peale of the Hayden Survey 

described the Florissant area in 1874, mentioning 20 or 30 

stumps visible above ground. In a history of the 

Florissant valley, Kimmet (1986) asserted that an “early 

photo of the forest shows such a profusion of petrified 

stumps, limbs, and branches that the area seemed almost 

impassable.” By 1882, however, geologists were already 

complaining of “vandal tourists” breaking up the stumps 

and logs and hauling them away (Kimmet, 1986). Material 

was removed until 1969, when the area became a national 

monument; the only stumps left were those too large to 

be moved or those still buried. In 1984 the National Park 

Service reburied some stumps to prevent vandalism and 

further deterioration (Gregory- Wodzicki, 2001). 

In the remaining stumps, cellular details of the anatomy 

and structure of the trees can still be observed in the 

preserved wood, which have enabled paleobotanists to 

identify the wood types (primarily Sequoia- like trees) 

and to examine tree growth rings for information about 

paleoclimate (Wheeler, 2001). Tree rings are the result of 

varying seasonal growth rates. During spring and 

summer when growing conditions are favorable, the 

trees add large cells to their outer layer of wood. When 

the cold, dry winter comes, smaller cells are added. The 

two types of cells give the appearance of light and dark 

rings (figure 7). These rings can provide clues to the age 

of trees, climatic conditions, and fire and disease history 

(Florissant Fossil Beds National Monument, Petrified 

Forest Walk). 

Fossil Spiders, Insects, and Myriapods 

The extensive fossil record of the Florissant Formation is 

notable for the outstanding details, number, and 

diversity of the delicate, preserved remains of insects. 

Just as in modern environments, spiders and insects are a 

hugely diverse group, with more than 1,500 species 

described from Florissant. Future studies may compress 

the number of described species of Florissant spiders and 

insects into a smaller number of valid species. At the 

same time, researchers may add descriptions of new 

species. 

Fossil insects include flies (e.g., march, dance, bee, hover, 

and tsetse), mayflies, scorpion flies, katydids, crickets, 

mantids, moths, cockroaches, termites, earwigs, 

waterscorpions, leafbugs, assassin bugs, froghoppers, 

cicadas, aphids, lacewings, beetles and ladybugs, wasps, 

bees, and ants. The 12 species of fossil butterflies from 

Florissant provide the world’s richest diversity of fossil 

butterflies (Meyer and Weber, 1995). 

The myriapods are a group of multi- legged arthropods 

including centipedes and millipedes. At Florissant the 

group is represented by the class Diplopoda (millipedes) 

and includes two families, each with a single species 

(Meyer, 2003). The reclusive lifestyle of millipedes 

explains their rarity in the fossil record. 

Because of the unusual taphonomic (burial) conditions 

required for their preservation, spiders and insects are 
20 NPS Geologic Resources Division 

much less common than plants in the world’s fossil 

record, making their occurrence at Florissant even more 

significant. Fossil plant sites abound globally, but insect 

sites are rare. The abundance of insects at Florissant 

results partly from the unusual conditions of taphonomy, 

facilitated largely by the presence of diatom mats, which 

provided a rare mechanism of entrapment favoring 

insect preservation (Meyer, 2003). Fossil insects at 

Florissant typically consist of entire bodies. The different 

parts of a spider or insect are usually preserved “in 

attachment,” making it easier for scientists to reconstruct 

the entire organism. 

Ostracods and Mollusks 

According to Meyer (2003), invertebrates other than 

insects and spiders at Florissant include a species of 

ostracod (Cypris florissantensis [mussel shrimp]) and 

both freshwater and terrestrial mollusks. The most 

abundant and diverse group of mollusks at Florissant are 

gastropods (snails). Only one species of freshwater clam, 

questionably placed in the genus Sphaerium, has been 

described. 

Vertebrate Fossils 

Vertebrate fossils are rare at Florissant. For the most part 

we are left to wonder what kinds of vertebrate animals 

once lived here. The rarity of vertebrate fossils at 

Florissant is the result of taphonomic biases and the 

nature of sedimentary environments in which the fossils 

were preserved. In part, terrestrial vertebrates are rare in 

lake deposits simply because it was uncommon for their 

dead carcasses to be transported into the lake. In 

addition, acidity in the lake, caused by decaying plant 

material or volcanic ash falls, may have inhibited the 

fossilization of vertebrates by dissolving bone material 

(Meyer, 2003). 

Birds

Some vertebrate fossils do occur in the Eocene 

sediments, for example, three exemplary bird fossils, all 

from the lake shale units of the Florissant Formation. 

One specimen is tentatively identified as belonging in the 

Coraciiformes order (e.g., rollers and kingfishers). The 

phylogenetic relationships of the other two species are 

unclear and they have been placed into Aves: incertae 

sedis (“classification uncertain”). A particular fossil with 

an almost complete skeleton, except for the skull, is a 

very important find. This specimen has been described as 

a new genus and species, Eocuculus cherinae, with 

affinities to the arboreal cuckoos (Cucuiformes, 

Cuculindae, Cuculinae) of the Old World (Chandler, 

1999). Like the better known insects and plants, the 

extraordinary quality of the preservation is shown by the 

presence of feather impressions on the slab and counter 

slab of Eocuculus (Chandler, 1999). 

In 1997 the finest bird specimen to date to come from the 

Florissant fossil beds was uncovered: a complete, 

extremely well- preserved, new species possibly related 

to plovers, with long legs and extended beak (Meyer, 

2003). “New discoveries such as this assure that the study 

of Florissant’s paleontology remains an exciting story, 

and one that is never completely concluded” (Meyer, 

2003). 

Fish

Fish are the most abundant vertebrate fossils at 

Florissant. They include bowfins, suckers, catfishes, and 

pirate perches. During the mid- 1870s, E. D. Cope 

originally described the Florissant fish, at the same time 

he was describing dinosaurs from Jurassic deposits a few 

miles south of Florissant. 

Most of the Florissant fish, except for pirate perches, 

were bottom dwellers, and many were tolerant of poor 

water conditions. Fossil fish seem to be more common in 

some shale layers than others, perhaps indicating that 

water conditions in the lake changed through time 

(Meyer, 2003). 

Mammals

Until recently, discoveries of fossil mammals have been 

serendipitous. Mammal fossils found in the Florissant 

Formation include an entire body of a small extinct 

mouse opossum (Peratherium), fragmentary remains of a 

small, three- toed horse (Mesohippus), brontothere (an 

extinct rhinoceros- like animal), and oreodont (an 

extinct ungulate, resembling a pig). However, in summer 

2003 a systematic investigation of the fluvial lower 

mudstone unit greatly increased the known mammal 

diversity from the Florissant Formation (Worley, 2004). 

The discovery of a single large molar confirms the 

presence of eubrontotheres in the monument, which had 

been inferred previously from a large atlas and tooth 

enamel fragments. Two artiodactyls taxa are represented 

by isolated lower molars, Leptomeryx cf L. speciosus, and 

a second yet to be identified. Additionally, the rodents 

Eutypomys parvus, Adjidaumo minimus, Pelycomys, and 

Ischyromys douglassi occur as Florissant mammalian 

fauna. Worley also recovered insectivoran jaws, 

representing the soricid Domnina thompsoni, the 

geolabidid Centetondon magmun, and a tiny proscalopid 

(Worley, 2004). 

In addition, Quaternary deposits at the monument have 

yielded mammoth bones, including a molar with an 

associated portion of the jaw, dated at 49,830 ± 3,290 

years B.P. (Meyer, 2003). 

Unconformities 

Unconformities are “gaps in the rock record” during 

which either no rocks were deposited, or since 

deposition have been eroded away. Tertiary rocks of the 

Florissant area lie unconformably on the eroded surface 

of the Pikes Peak Granite. The unconformity represents 

a long interval of erosion that followed Precambrian 

mountain building. Many thousands of feet of rock were 

removed, thereby exposing the deeper crystalline 

mountain roots. Paleozoic seas swept across the area 

burying the ancient erosion surface with sediment and 

producing a major unconformity. In Florissant, late 

Eocene streams cut a long dendritic valley into the 

exposed Precambrian rocks, in which volcanic rocks and 

sediment later accumulated. Local relief on this 
FLFO Geologic Resource Evaluation Report 21 

unconformity is as great as 980 feet (300 m) near the 

southern end of the paleovalley (Evanoff and others, 

2001). This particular break in the rock record represents 

more than 1.04 billion years of missing time. All 

Paleozoic, Mesozoic, Paleocene, and early Eocene rocks 

have been eroded away. 

The youngest unconformity rests above the pumice 

conglomerate unit of the Florissant Formation and 

represents missing time from the Oligocene, Miocene, 

and Pliocene Epochs (see figure 1). These rocks were 

stripped away by erosion. The unconformity is locally 

capped by Quaternary deposits and represents about 32 

million years of missing time. 

Another unconformity, less conspicuous than the one 

that separates Precambrian and Tertiary rocks in the 

area, lies between the Wall Mountain Tuff (Eocene) and 

the next youngest rocks that remain. Not all rocks 

eroded evenly at all locales. Depending on the exposure, 

this may be between the Wall Mountain Tuff and 

Florissant Formation or between the Wall Mountain 

Tuff and the boulder conglomerate. This unconformity 

represents missing time (hiatus) during the Eocene 

Epoch. 

Tors 

Tors are isolated rock towers that rise prominently above 

otherwise level terrain. At Florissant they are composed 

of Precambrian Pikes Peak Granite, which is very jointed. 

Tors may assume peculiar or fantastic shapes. 

Investigators think that periglacial processes may be 

important in the formation of tors (Bates and Jackson, 

1987). Investigators also have identified tors as indicators 

of non- glaciation (Street, 1973). Tors remain in areas that 

were beyond the limit of glaciation; otherwise, glaciers 

would have modified or destroyed them. 

Sedimentation and Fossilization 

The pattern of sedimentation in Lake Florissant is 

significant for the ultimate preservation of fossils. In past 

descriptions, volcanism is given full credit for 

fossilization; however, more recently, the story has 

become more complicated, albeit more accurate. For 

example, Kiver and Harris (1999) state, 

Here, insects and plants were snuffed out rapidly 

as ash fell in large volumes. Both ash and insects 

settled to the bottom of Lake Florissant and 

compression under the weight of additional 

sediment and rock produced carbon films. The 

finer than talcum- powder- size ash faithfully 

preserves minute anatomical details enabling 

paleontologists to study everything except 

internal organs and the original color of insects. 

Delicate antennae, legs, and hairs on the bodies 

are often preserved. Butterfly and moth wings 

often show the patterns of spots and other 

markings. 

This description of the fossils is accurate, but the process 

of fossilization lacks a significant component. Although 

some of the ash that ended up in the lake was directly 

deposited from the atmosphere, as Kiver and Harris 

describe, much of the ash had fallen across the landscape 

and later washed into Lake Florissant. Moreover, most of 

the ash and pumice layers are sparsely fossiliferous or 

entirely devoid of fossils because they were deposited 

too rapidly and are too coarse in texture to incorporate 

and preserve delicate plants and insects. 

The silica- rich ash weathered into clay and washed into 

the lake, enriching the lake’s chemistry. Weathering, 

therefore, is now recognized as a significant step in the 

fossilization process at Florissant (Harding and Chant, 

2000; O’Brien and others, 2002; O’Brien and others, 

1998). The abundance of silica in the lake allowed 

diatoms—microscopic algae—to live and form hard 

siliceous shells. Periodically, diatoms bloomed into 

abundant populations, which were followed by massive 

die- offs caused by overpopulation that depleted lake 

water of silica and other nutrients. As the diatoms died, 

billions upon billions of their microscopic siliceous shells 

settled to the lake bottom, forming a thin layer above the 

layer of ash- clay. The micro- layers of ash- clay and 

diatoms compacted to form the well- known “paper 

shales.” Geologists refer to the lake beds as shale because 

of their clay content and laminated character. Explicitly 

calling them diatomaceous tuffaceous shales highlights 

the significance of the two- fold sedimentation process 

that includes (1) diatoms and ash- clay layers and (2) 

volcanic ash eruptions. 

Identifying the process of sedimentation is important for 

understanding the preservation of fossils at Florissant: 

plants and insects became entrapped in mucoussecreting mats of surface water blooms of planktonic 

diatoms in Lake Florissant. As the mats and incorporated 

organisms settled out of the water column, the 

mucilaginous mats and their associated bacterial 

communities arrested decay and promoted preservation 

of refractory tissues. Thus, ash fall and the diatom mats 

preserved the fossils in Lake Florissant. Moreover, 

diatom mats preserve soft tissue in a way previously 

suggested for cyanobacterial mats (Harding and Chant, 

2000). Generally speaking, this mode of preservation 

may be an important causative factor in the formation of 

exceptionally preserved lacustrine fossil biota like those 

at Florissant. 
22 NPS Geologic Resources Division 

Figure 7. Tree Growth Rings of Petrified Wood. Paleontologists examine tree growth rings, which are a result of varying seasonal 

growth rates, for information about paleoclimate. Cellular details of the wood’s anatomy and structure can still be observed in petrified 

wood at Florissant Fossil Beds National Monument. Photo by Katie KellerLynn. 
FLFO Geologic Resource Evaluation Report 23 

Map Unit Properties 

This section provides a description for and identifies many characteristics of the map 

units that appear on the digital geologic map of Florissant Fossil Beds National 

Monument. The table is highly generalized and is provided for informational purposes 

only. Ground disturbing activities should not be permitted or denied on the basis of 

information contained in this table. More detailed unit descriptions can be found in the 

help files that accompany the digital geologic map or by contacting the National Park 

Service Geologic Resources Division. 

Geologists have mapped and described the rocks and 

unconsolidated deposits that occur in Florissant Fossil 

Beds National Monument, and from this, they have 

deciphered the nature and sequence of geologic events. 

The geology of Florissant is composed of three formal 

units: Pikes Peak Granite, Wall Mountain Tuff, and the 

Florissant Formation; one informal unit—boulder 

conglomerate (equivalent to the Tallahassee Creek 

Conglomerate); and three deposits of Pleistocene or 

Holocene age: gravels, alluvium, and colluvium. 

The table that comprises this section is meant to 

complement the digital geologic map of Florissant Fossil 

Beds National Monument (see included CD). The map 

units listed in the table correspond to this geologic map; 

however since 1992, Evanoff and others (2001) updated 

and divided the Florissant Formation into six units, with 

the addition of the lower shale unit. The five 

alphanumeric designations (Tf1, Tf2, Tf3, Tf4, and Tf5) 

were used for classification of mapped outcrops in the 

monument, but were not intended to be used outside the 

monument. The six informal units of the Florissant 

Formation are from oldest to youngest (bottom to top) 

(1) lower shale unit, (2) lower mudstone unit (referred to 

as Tf1), (3) middle shale unit (referred to as Tf2), (4) cap 

rock conglomerate unit (referred to as Tf3), (5) upper 

shale unit (referred to as Tf4), and (6) upper pumice 

conglomerate unit (referred to as Tf5). Although the 

lower shale unit does not occur within the monument’s 

boundary and is not included on the geologic map, it has 

been included in the table in order to provide a full 

description of the Florissant Formation and to complete 

the geologic story that includes two generations of Lake 

Florissant. 
Map Unit Properties Table 

Age Unit Name (Symbol) Description Depositional Setting Local and Global S

Colluvium (Holocene and Pleistocene) (Qc) 

Thin gravels mantling slopes, composed of granular grus derived from the Pikes Peak Granite, rhyolitic gravel derived from the Wall Mountain Tuff, and shale, mudstone, sandstone, and silicified wood fragments derived from the Florissant Formation 

Brought to the foot of a slope or cliff by gravity None 

Holocene alluvium 

(Qal) Brown unconsolidated humus- rich (peat) sands and gravelly sand Occurs along streams None 

Quaternary 

Pleistocene gravels 

(Qg) 

Thick gravels mainly composed of granular grus derived from the Pikes Peak Granite, also scattered fragments of Wall Mountain Tuff 

Stream deposits (alluvial fan and terrace) None 

unconformity 

Unit 5 (Tf5) 

Upper pumice conglomerate unit: pumice- rich white sandstones and 

conglomerates, structureless to locally trough cross- bedded; numerous pink pumice clasts near top; poorly sorted brown pumiceous sandstones interbedded with scattered lenticular mudstones and shales (near south entrance); maximum measured thickness 75 ft (22.8 m). 

Lacustrine at base (deposited in Lake Florissant), fluvial at top (streams in tributary valleys washed pumice pebbles into lake) 

Age: 34.07 ± 10 Ma (basedating); dates come from Tf5 (Evanoff and others

Unit 4 (Tf4) 

“Upper lake shale” (upper shale unit): gray to greenish- brown paper shales and 

blocky mudstones; interbedded with planar, thin yellow to white pumiceous sandstone beds; maximum measured thickness 18 ft (5.6 m) in the NW corner of the monument; unit thins to the south. 

Lacustrine (represents younger generation of Lake Florissant) Prolific fossil- bearing u

Unit 3 (Tf3) 

“Cap rock” (cap rock conglomerate unit): yellowish- gray conglomerate with 

subangular to rounded clasts of tuff, quartz, and andesite; locally contains blocks of andesite, pumiceous sandstones, and blocky mudstone; typically graded, otherwise structureless to crudely horizontally bedded; maximum thickness 26 ft (7.9 m) measured near Lodge stump (E of Scudder pit); thins to the north and is not present in the NW corner of the monument. 

Volcanogenic debris: flow deposit in Lake Florissant, later reworked by lacustrine processes; vertical tubes represent water- escape structures 

Protects Tf2 from erosio

Unit 2 (Tf2) 

“Lower lake shales” (middle shale unit): interbedded brown paper shales, grayish 

brown blocky mudstones, thin yellowish pumiceous sandstones, and thin granular pumice conglomerates; maximum thickness 30 ft (9 m). 

Lacustrine (represents younger generation of Lake Florissant); also may represent marginal swamp environments; volcanic fallout in lake 

Most of the fossil quarriunit (e.g., Princeton quaTennessee pit) 

Unit 1 (Tf1) 

“Lower fluvial sequence” (lower mudstone unit): tan to gray blocky tuffaceous 

mudstones interbedded with yellowish gray pumiceous sandstones and rare arkosic sandstone ribbons, which typically have abundant trough cross- bedding; bottom contact poorly exposed; maximum thickness 34 ft (10.4 m). 

Fluvial (with rare channel deposits) topped by a volcanogenic mudflow deposit on valley bottom; not in Lake Florissant 

Upper 16 feet (5 m) is a sdeposit that buried stumassociated with down- vthat dammed Lake Flori

Florissant Formation 

 Lower shale unit: alternating tuffaceous siltstone and paper shale beds (alternating 

laminae of diatomite and volcanic ash altered to smectite clays); thin pumice conglomerate with granite and volcanic clasts scattered throughout. Note: Florissant Fm. underlies about one- third of monument; total thickness 23 ft (75m) 

Lacustrine (represents earlier Lake Florissant) 

Lowest occurrence of prshales 

Tertiary 

(Eocene) 

Boulder Conglomerate (Tb) 

Lenticular boulder conglomerate composed primarily of large rounded blocks of Pikes Peak Granite, and secondarily of gneiss and rhyolite cobbles and boulders; rhyolite clasts rounded to subangular and derived from the Wall Mountain Tuff; interbedded with Tf1, and rests on surface cut into the Wall Mountain Tuff and the Pikes Peak Granite; maximum thickness about 49 ft (15 m). 

Fluvial and debris- flow deposit 

Probable equivalent of thCreek Conglomerate expWrights Reservoir (Wob1978) 

unconformity

Tertiary 

(Eocene) Wall Mountain Tuff (Twm) Rhyolitic welded tuff, brownish- gray to dark gray; abundant sanidine and less abundant biotite, argillized plagioclase, and magnetite; weathers to large angular to subangular blocks; maximum thickness 49 ft (15 m) in lower exposures. Pyroclastic flow from the southwest (probable source is Mount Princeton batholith), strongly controlled by paleotopography, mantles sides of the 

Florissant paleo- valley 

Oldest Tertiary rock in t37.73 ± 0.07 Ma (average reported by McIntosh an

unconformity

Precambrian Pikes Peak Granite (pCg) Medium to coarsely crystalline reddish granite and quartz monzonite; contains abundant perthitic microcline, quartz, and biotite; contains micro- joints. Emplaced during a time of crustal extension, perhaps associated with continental epeirogenic uplift and doming Oldest rocks in the monu

among the youngest ProColorado—1.08 Ga (Unr1995), Lake Florissant foeroded surface of this un

Sources: Evanoff (1992, 1994), Evanoff and others (2001), Gregory- Wodzicki (2001), Meyer (2003), Wobus (2001). *Diatom mats were originally interpreted as stromatolites (Evanoff and Doi. 1992). 
FLFO Geologic Resource Evaluation Report 25 

Geologic History 

This section highlights the map units (i.e., rocks and unconsolidated deposits) that occur 

in Florissant Fossil Beds National Monument and puts them in a geologic context in 

terms of the environment in which they were deposited and the timing of geologic events. 

The late Eocene deposits at Florissant Fossil Beds 

National Monument, with their world- famous plant and 

insect fossils, lie in a paleovalley incised into Pikes Peak 

Granite, the oldest rocks in the monument (about 1.08 

billion years old) (Wobus, 2001). The Pikes Peak 

batholith, formed when the granite cooled from magma 

deep beneath Earth’s surface, is bounded on all sides by 

older batholiths and plutons. The intrusive episode that 

formed the Pikes Peak Granite is the last of three events 

that occurred at about 1.7, 1.4, and 1.0 billion years ago. 

The oldest rocks in the area, into which these batholiths 

intruded, consisted of a combination of regionally 

metamorphosed sediments (dominantly marine 

mudstones) and some volcanic rocks. Emplacement of 

the Pikes Peak Granite, the last of the Precambrian 

(figure 1) igneous events, was more localized than the 

other two igneous episodes. It is the largest Precambrian 

pluton in the southern Rocky Mountains. Emplacement 

probably occurred during a time of crustal extension or 

rifting, rather than mountain building; the event formed 

the basement rock of the present- day monument. 

The Precambrian crystalline rocks of Florissant were 

uplifted, beginning most recently about 70 million years 

ago during the Laramide orogeny. As mountain- building 

and uplift progressed, layers of previously deposited 

Paleozoic and Mesozoic rocks were eroded from the 

uplifted area and redeposited as sediments in the 

surrounding Denver and South Park basins. Because of 

uplift during the Laramide orogeny, Pikes Peak Granite, 

forming the core of the uplift, was exposed at the surface. 

Erosion cut an irregular surface into the exposed granite, 

creating an unconformity at Florissant, and streams cut a 

long dendritic valley. Pikes Peak Granite is exposed as 

boulders, tors, and isolated knobs and hills on the flanks 

of the paleovalley. 

Wall Mountain Tuff rests unconformably on the 

irregular erosion surface of Pikes Peak Granite and 

mantles the sides of the paleovalley. About 37 million 

years ago, during a time of increased volcanic activity, a 

thick pyroclastic flow followed drainages and draped 

welded tuff over the local topography. The ash flow that 

produced the Wall Mountain Tuff must have been a 

tremendous event. The Wall Mountain Tuff is a welded 

tuff (ignimbrite) that formed from a hot (1,292°F 

[>700°C]) cloud consisting of volcanic glass, crystals, 

rock fragments, and hot gases (nuée ardente). No one in 

modern times has observed an eruption that has 

produced a volume of tuff the size of Wall Mountain 

Tuff, but such eruptions have been modeled using their 

rock records as constraints. During such events, the hot 

material probably erupts in such a huge vertical column 

that the column collapses and flows along the 

topography like a very hot, subaerial turbidity current. 

This hot flowing mass can be more than a mile thick and 

travel at velocities greater than 225 miles per hour (100 

m/sec) (Cas and Wright, 1987). As the cloud slows, the 

liquid and solid components settle and blanket the 

topography, with low areas receiving the thickest 

mantles. Also as the cloud settles, the hot glass particles 

coalesce and weld together. The Wall Mountain Tuff is 

welded even in its farthest reaches, indicating it had to be 

formed quickly to retain its heat. Considering the 

velocity of such pyroclastic flows, the tuff may have been 

deposited over its 4,015- square- miles (10,400- km2

) 

extent within an hour or two (McIntosh and Chapin, 

1994). Wall Mountain Tuff has also provided the basis for 

reconstructing regional paleodrainages (Epis and 

Chapin, 1975). 

The source of the tuff was a volcanic center near 

present- day Mount Princeton, about 129 miles (80 km) 

west of the monument. An immense caldera formed 

when the eruptive center collapsed into the depleted 

magma chamber following the eruption. Although this 

caldera was large, it is no longer evident in the modern 

topography. 

A limited exposure of boulder conglomerate overlies the 

Pikes Peak Granite and Wall Mountain Tuff on the 

southeastern side of the monument. This conglomerate 

is equivalent to the Tallahassee Creek Conglomerate and 

contains huge boulders and cobbles of granite; the 

largest boulders span 19 feet (5.8 m) in diameter. The 

conglomerate also contains cobbles and boulders of 

gneiss, schist, welded tuff (from the Wall Mountain 

Tuff), and scattered silicified wood fragments. The 

conglomerate was deposited by streams and debris flows. 

The primary fossil- bearing rocks in the area make up the 

Florissant Formation. The Florissant paleovalley was 

episodically dammed by volcaniclastic debris flows 

(lahars) derived from the Thirtynine Mile volcanic field, 

including the massive Guffey volcano, to the southwest. 

Like modern stratovolcanoes, the Guffey volcano was 

active sporadically over a long period, perhaps several 

hundred thousand years (Meyer, 2003). Lahar activity 

progressed northward into the paleovalley and acted as 

dams to the Florissant valley drainage, creating the 

ancient Lake Florissant. Lahars also covered the forest 

floor and buried the stumps that would become the 

petrified forest. Therefore, the Florissant Formation is 

not simply composed of “lake beds” but contains a 

variety of lithologies, including sandstone, siltstone, 

shales, mudstone, and conglomerate. Scientists have 

estimated the duration of Lake Florissant to be about 
26 NPS Geologic Resources Division 

2,500 to 5,000 years (McLeroy and Anderson, 1966). The 

source of the ash and pumice that make up the Florissant 

Formation is unknown, although investigators have 

speculated about some options: (1) early, pre- ignimbrite 

eruptions from the 33.8- million- year- old (Ma) Mount 

Aetna caldera, (2) late, post- ignimbrite eruptions from 

the 34.3- Ma Grizzly Peak caldera, (3) eruption of a local 

rhyolite dome in the vicinity of Florissant (Evanoff and 

others, 2001), and (4) the Guffey volcanic complex. 

At the time of deposition of the late Eocene fluvial, 

lacustrine, and volcanic rocks in paleovalleys at and near 

Florissant, the topography of the region probably 

resembled that of today, controlled by the relative 

resistance of the Proterozoic (Precambrian) rocks. 

Ridges and hills, then as now, were supported by the 

more resistant, fine- grained rocks. In contrast, the most 

common but least resistant rock in the area, coarsegrained Pikes Peak Granite, produced a more subdued 

surface often thickly mantled with grus. Not surprising, 

then, the paleovalley which became the site of Lake 

Florissant was developed in this most highly erodible 

Proterozoic unit (Wobus, 2001). 

One topographic difference from today was that the 

Florissant Formation was deposited within a valley that 

then drained to the south. Land that had been draining 

into the Arkansas River now drains into the Platte. The 

modern drainage divide that separates the Platte and 

Arkansas drainages occurs within the area of 

paleodrainage and is located just south of the monument. 

This reversal in streamflow direction indicates tilting 

after deposition of the Florissant Formation and after the 

valley was buried by volcanics and sediment (Evanoff, 

1992). 

The present topography of the region is probably the 

result of Laramide uplift and subsequent erosion later in 

the Cenozoic (Pederson and others, 2002). This 

interpretation is based on a method that uses 

geographical information system (GIS) to evaluate the 

history of erosion and uplift. However, though the 

mechanism is becoming clear, the actual elevation of 

Florissant 34 million years ago is still a controversial 

enigma. Recent paleobotanical estimates argue that the 

late- Eocene elevation was at or exceeded its present 

elevation, subsequently subsiding. However, some 

geologists remain skeptical of this interpretation and 

argue that post- Laramide uplift has been extensive, 

which suggests a lower Eocene elevation. In either case, 

Florissant fossils remain a means for solving this 

controversial issue. 

Most of the rocks that covered the Florissant Formation 

before the beginning of the Pleistocene Epoch have been 

stripped away by erosion. However, some remnants are 

still present, including later volcanic lava flow deposits 

from the Guffey volcano. For example, during the later 

part of Tertiary time, sand and gravel deposits formed a 

layer that is now exposed several miles to the east of 

Florissant, near Divide, Colorado (Meyer, 2003). The 

erosional episode that occurred between the Eocene and 

the Pleistocene, which stripped the rocks from the 

Florissant Formation, created this unconformity in the 

monument. 

During the ice ages of the Pleistocene Epoch, glaciers 

were present only on the highest reaches of Pikes Peak 

and did not extend into the Florissant valley. At 

Florissant, Pleistocene deposits consist of sand and 

gravel from weathered Pikes Peak Granite, Wall 

Mountain Tuff, and fragments of shale, mudstone, 

sandstone, and silicified wood derived from the 

Florissant Formation. These deposits, composed of 

debris accumulation along the bases of slopes and from 

sediments washed into the valleys by streams, form a thin 

mantle above the Florissant Formation. Investigators 

have found fossil mammal bones, including mammoth, in 

these sediments. Typical erosion patterns in hilly country 

have taken their toll on the fossil beds. Today bits and 

pieces of the beds are exposed around the perimeter of 

the old lake. 
FLFO Geologic Resource Evaluation Report 27 

References 

This section provides a listing of references cited in this report. A more complete geologic 

bibliography is available and can be obtained through the National Park Service 

Geologic Resources Division. Additionally, the Florissant Fossil Beds National 

Monument Web site hosts a database of paleontological references, which includes 

digital files of many of the older references. 

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528 p. 

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species of Cuckoo, in Santucci, V.L., and McClelland, 

L., eds., National Park Service paleontological research 

4: Geologic Resources Division Technical Report, 

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Eocene erosion surface in the southern Rocky 

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1980, Summary of Cenozoic geomorphic, volcanic, and 

tectonic features of central Colorado and adjoining 

areas, in Kent, H.C., and Porter, K.W., eds., Colorado 

geology: Denver, Rocky Mountain Association of 

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Evanoff, E., 1992, Introductory remarks on the geology 

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stratigraphy and paleontology of Florissant Fossil Beds 

National Monument—a progress report 

[unpublished]: Boulder, Colorado, University of 

Colorado Museum, p. 1- 1–1- 30. 

Evanoff, E., ed., 1994, Late Paleogene geology and 

paleoenvironments of central Colorado with emphasis 

on the geology and paleontology of Florissant Fossil 

Beds National Monument, Guidebook for the field 

trip May 6–8, 1994: Boulder, University of Colorado 

Museum, 99 p. 

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paleontology of Florissant Fossil Beds National 

Monument—a progress report [unpublished]: 

Boulder, University of Colorado Museum, 169 p. 
28 NPS Geologic Resources Division 

Evanoff, E., Brill, R.A., de Toledo, P.M., Murphey, P.C., 

and Cushman, R.A. Jr., 1992, Surficial geologic map of 

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plate 1, scale 1:10,000. 

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administrative facilities: Washington, D.C., National 

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of seven earthen dams, Florissant Fossil Beds National 

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Gregory, K.M., 1994a, Paleoclimate and paleoelevation of 

the 35 Ma Florissant flora, Front Range, Colorado: 

Palaeoclimates, v. 1, p. 23–57. 

Gregory, K.M., 1994b, Paleoclimate and paleoelevation 

of the Florissant flora, in Evanoff, E., ed., 1994, Late 

Paleogene geology and paleoenvironments of central 

Colorado with emphasis on the geology and 

paleontology of Florissant Fossil Beds National 

Monument, Guidebook for the field trip May 6–8, 

1994: Boulder, University of Colorado Museum, p. 59–

68. 

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significance of paleobotanically estimated climate and 

altitude of the late Eocene erosion surface, Colorado: 

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and paleoelevation of the Oligocene pitch- pinnacle 

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implications of tree- ring growth characteristics of 34.1 

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reclamation project, Florissant Fossil Beds National 

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appendices. 

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reclamation project, Florissant Fossil Beds National 

Monument, Teller County, Colorado [draft document, 

unpublished, November 2001]: Greenwood Village, 

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appendices. 

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South Park: Mines and Minerals, v. 20, p. 179–180. 
FLFO Geologic Resource Evaluation Report 29 

Leopold, E.B., and Clay- Poole, S.T., 2001, Florissant leaf 

and pollen floras of Colorado compared—climatic 

implications, in Evanoff, E., Gregory- Wodzicki, K.M., 

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Denver, Colorado, Denver Museum of Nature & 

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beds, Colorado: Washington, D.C., Carnegie 

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National Monument—in celebration of preservation 

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Fossil Beds National Monument, 106 p. 

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geochronology of ignimbrites in the Thirtynine Mile 

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GIS: GSA Today, v. 12, no. 8, p. 4–10. 

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shale beds, Colorado [unpublished NPS report, D- 5, 

file 10]: National Park Service, 30 p. 

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Scott, G.R., and Taylor, R.B., 1986, Map showing late 

Eocene erosion surface, Oligocene- Miocene 

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30 NPS Geologic Resources Division 

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reference to their value as an indicator of nonglaciation [M.S. thesis]: Boulder, Colorado, University 

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Florissant Fossil Beds National Monument, Colorado, 

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K.R., eds., Proceedings of the Denver Museum of 

Nature & Science, Fossil flora and stratigraphy of the 

Florissant Formation, Colorado, ser. 4, no. 1, p. 187–

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metamorphic rocks in the Florissant region, central 

Colorado—their topographic influence, past and 

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lapse rates in the western conterminous United States 

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latitudes of western North America: Palaeogeography, 

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paleoaltitudes in midlatitude western North America: 

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Worley, M., 2004, New additions to the Chadronian 

mammalian fauna from the Florissant Formation, 

Florissant Fossil Beds National Monument, Florissant, 

Colorado [M.S. thesis]: Boulder, Colorado, University 

of Colorado, 83 p. 
FLFO Geologic Resource Evaluation Report 31 

Appendix A: Geologic Map Graphic 

The following page provides a preview or “snapshot” of the geologic map for Florissant 

Fossil Beds National Monument. For a poster size PDF of this map or for digital geologic 

map data, please see the included CD or visit the GRE publications webpage: 

http://www2.nature.nps.gov/geology/inventory/gre_publications.cfm 

FLFO Geologic Resource Evaluation Report 33 

Appendix B: Scoping Summary 

The following excerpts are from the GRE scoping summary for Florissant Fossil Beds 

National Monument. The scoping meeting occurred on October 21, 1998; therefore, the 

contact information and Web addresses referred to herein may be outdated. Please contact 

to the Geologic Resources Division for current information. 

.

Agenda 

Meet at park headquarters 

9:00—Introductions, milling around 

9:15—NPS Geological Resources Inventory 

What we hope to accomplish (Bruce Heise, Geologic 

Resources Division [GRD]) 

9:30—Field Trip 

Geologic Setting, Geologic Issues Confronting the Park 

(park staffs and outside experts) 

12:00—Lunch (suggest a brown bag) 

12:30—NPS Geologic Resources Inventory, I&M, and 

GRD Program Overview (Bruce Heise and other GRD 

staff) 

1:15—Geological Resources Needs and Issues at FLFO 

(Herb Meyer, Tom Ulrich, other park staffs) 

2:00—GIS/Geologic Map/Digital Status (Sarah Beetch, 

Anne Poole) 

2:30—Continued Discussion 

• Additional park needs 

• Summary of USGS geological mapping and research 

• Other cooperators and discussion 

• Authors for report and/or other papers 

• Deliverables from mapping, cooperators, and NPS 

inventory 

4:45—Meeting Wrap- up and Feedback 

Workshop Cooperators 

Name Affiliation 

Bruce Heise NPS, Geologic Resources Division 

Tim Connors NPS, Geologic Resources Division 

Herb Meyer FLFO, Paleontologist 

Jean Rodeck FLFO, Superintendent 

Tom Ulrich FLFO, Chief Ranger 

Anne Poole BLCA/CURE, GIS 

Sarah Beetch BLCA/CURE, GIS 

Barb Mieras Geological Society of America 

Emmett Evanoff University of Colorado Museum 

Jim Wood NPS, Geologic Resources Division 

After introductions by the participants, Bruce Heise 

(filling in for Joe Gregson who could not attend the 

meeting) presented overviews of 

• NPS I&M Program 

• Status of both the natural and geologic resources 

inventories 

• Organization of the Natural Resource Stewardship and 

Science Washington Office, GRD, and the Colorado 

pilot project 

Afterward, Sarah Beetch and Anne Poole presented their 

progress on digital geologic maps. 

The main items of discussion for this workshop centered 

on the following: 

• Existing geologic maps 

• Park natural resource management needs 

• RMP statements 

• Usefulness of existing published literature to serve as a 

sufficient geologic report for the monument 

Geologic Maps 

Some of the available geologic maps (paper copies) come 

from the following sources: 

• Preston Louis Nieson (1969), New Mexico 

• Ralph Root (1981), USGS- BRD, this map has been 

digitized (Anne Poole held up a copy); however, 

questions arose about problems with this map (i.e., it 

was digitized off of copies, and Emment Evanoff 

disagrees with the denoted faults). Emmett would like 

to schedule some time in the field with Ralph Root to 

examine evidence for faults in the valley. According to 

park staff, this field work did occur (Herb Meyer, 

Florissand Fossil Beds National Monument, written 

communication, May 2, 2005). Ralph Root was with 

the NPS GIS Division. His map was digitized using 

Grass software and paper maps that were spliced 

together. Also, GIS folks from Curecanti National 

Recreation Area were concerned that the existing 

maps do not extend beyond the park boundary. 

• Evanoff and others (1992), University of Colorado at 

Boulder—surficial map 

• Evanoff (1994), University of Colorado at Boulder; this 

map is published in a 1994 Geological Society of 

America field guide and was deemed sufficient by the 

group to serve as the geologic map to use for our 

report. However, Evanoff believes we should have a 

map that shows the breakdown of the Florissant 

Formation units as he sees them. He says he can get a 

map together in a month or so. 

Needs 

Some of the addressed needs for Florissant Fossil Beds 

included 

• Better Quaternary map 
34 NPS Geologic Resources Division 

• Paleontology intern for working on Web pages—Tom 

Ulrich specifically mentioned Marc Duggan. Tom was 

trying to help Marc find some work with us. He said 

Marc is going to help them, but wanted to know if we 

were interested in picking him up to work on our 

projects out of Fort Collins. 

• Students/interns—semester students were preferred 

over quarter students because of the starting times 

(available May through August when housing was 

most likely to be provided by the park; cannot offer 

housing in September). 

• Funding—Tom Ulrich mentioned that the park has 

applied for a Canon grant to support a winter/spring 

intern to work on park databases and environmental 

education programs. 

• Fee money for excavations ? 

• Park brochure—FLFO staff is looking into redesigning 

their park brochure through Harpers Ferry Center and 

may need additional funding. The redesign will 

remove the “age of mammals” thematic panel and 

replace it with a park map and park specific 

information. Staff at Florissant Fossil Beds National 

Monument and other fossil parks have expressed a 

desire to develop a Servicewide NPS fossils thematic 

brochure. 

RMP Statements 

• According to Tom, Herb Meyer has done an excellent 

job in developing and implementing RMP statements 

since his arrival. 

• The park’s proposals for GeoScientist- in- the- Parks 

funding from the Geological Society of America are 

closely tied to existing RMP statements and offer a 

diverse range of experiences and training. 

Report 

A geologic report for the monument could be generated 

from one of the following notable publications: 

• Herbert W. Meyer and Laine Weber $1.00 publication 

that can be found in the bookstore entitled 

“Preservation of an Ancient Ecosystem.” Herb is also 

currently writing a summary of the paleontological 

features of the monument; his database is his major 

source of documentation for this. 

• Emmett Evanoff’s 1994 GSA field guide 

• Emmett Evanoff’s 1992 ring binder that was compiled 

for a field course that he taught at Florissant 

• Ralph Root’s 1981 report that accompanies his maps 

• Jim McChristal files on early history of geology of area 

• The topic of “disturbed lands” from past agricultural 

activities and subsequent dams was also discussed and 

should be mentioned in the report. Alex Birchfield 

(CSU) and Tom Ulrich are working on developing 

models to estimate the failure potential for some of 

these artificial retention structures. Given the potential 

for failure, it is possible that any breaching of these 

structures can serve as a major threat to the natural 

resources of the monument. Any publications on this 

subject should be incorporated into this final report. 

• Also, both the Evanoff and Meyer reports have good 

references. 

Action Items 

1. Evanoff will return to the area in November to 

complete mapping of the monument to fill in what he 

feels are gaps in the breakdown of the Florissant 

Formation members (as he sees them). He feels he can 

be finished around Thanksgiving. Soon after he felt he 

could turn over the maps to Beetch and Poole for 

digitizing. 

2. Evanoff mentioned that he has detailed stratigraphic 

sections that he will provide for the report. He also has 

designated a few type sections within monument 

boundaries and will provide write- ups on those as 

well. Connors needs these as part of a preliminary 

inventory and will pursue getting this information. 

3. It was mentioned that several of the older paper maps 

are out of print and unavailable at this time. Heise will 

look into the ability of the USGS to update maps and 

reprint out of stock originals (I- 1044 was specifically 

mentioned). 

4. Evanoff mentioned that he would soon be conducting 

research in Badlands National Park; he should be 

added to the list of cooperators for that park because 

of his help and interest at Florissant Fossil Beds 

National Monument. 

Overview of Geologic Resources Inventory 

The NPS Geologic Inventory is a collaborative effort of 

the NPS Geologic Resources Division (GRD) and 

Inventory and Monitoring (I&M) Program with 

assistance from the U.S. Geological Survey (USGS), 

American Association of State Geologists (AASG), and 

numerous individual volunteers and cooperators at 

National Park System units, colleges, and universities. 

From the perspective of the Servicewide I&M Program, 

the primary focus (level 1) of the geological inventory is 

1. to assemble a bibliography of associated geological 

resources for National Park System units with 

significant natural resources, 

2. to compile and evaluate a list of existing geologic maps 

for each unit, 

3. to develop digital geologic map products, and 

4. to complete a geologic report that synthesizes much of 

the existing geologic knowledge about each park. 

The emphasis of the inventory is not to routinely initiate 

new geologic mapping projects, but to aggregate existing 

information and identify where serious geologic data 

needs and issues exist in the National Park System. 

The NPS Geologic Resources Division is an active 

participant in the I&M Program and has provided 

guidance and funding in the development of inventory 

goals and activities. The Geologic Resources Division 
FLFO Geologic Resource Evaluation Report 35 

(GRD) administers the Abandoned Mine Lands (AML) 

and GeoScientists- in- the- Parks (GIP) programs, which 

contribute to the inventory. NPS paleontologists, 

geologists, and other natural resource professionals also 

contribute to inventory planning and data. A major goal 

of the collaborative effort is to provide a broad baseline 

of geologic data and scientific support to assist park 

managers with Earth resource issues that may arise. 

For each National Park System unit, a cooperative group 

of geologists and NPS personnel (the Park Team) will be 

assembled to advise and assist with the inventory. Park 

Teams will meet at the National Park System unit to 

discuss and scope the geologic resources and inventory, 

which is the subject of this report. If needed, a second 

meeting will be held at a central office to evaluate 

available geologic maps for digital production. After the 

two meetings, digital geologic map products and a 

geologic report will be produced. The report will 

summarize the geologic inventory activities and basic 

geology topics for each park unit. Because of the variety 

of geologic settings throughout the National Park 

System, each report will vary in subject matter covered, 

and section topics will be adapted as needed to describe 

the geologic resources of each unit. Whenever possible 

the scientific sections of the report will be written by 

knowledgeable cooperators and peer reviewed for 

accuracy and validity. 

The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and other 

information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated Island 

Communities. 

Florissant Fossil Beds National Monument 

Geologic Resource Evaluation Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2006/009 

NPS D-37, March 2006 

National Park Service 

Director • Fran P. Mainella 

Natural Resource Stewardship and Science 

Associate Director • Michael A. Soukup 

Natural Resource Program Center 

The Natural Resource Program Center (NRPC) is the core of the NPS Natural Resource Stewardship and 

Science Directorate. The Center Director is located in Fort Collins, with staff located principally in 

Lakewood and Fort Collins, Colorado and in Washington, D.C. The NRPC has five divisions: Air 

Resources Division, Biological Resource Management Division, Environmental Quality Division, Geologic 

Resources Division, and Water Resources Division. NRPC also includes three offices: The Office of 

Education and Outreach, the Office of Inventory, Monitoring and Evaluation, and the Office of Natural 

Resource Information Systems. In addition, Natural Resource Web Management and Partnership 

Coordination are cross-cutting disciplines under the Center Director. The multidisciplinary staff of NRPC 

is dedicated to resolving park resource management challenges originating in and outside units of the 

national park system. 

Geologic Resources Division 

Chief • David B. Shaver 

Planning Evaluation and Permits Branch Chief • Carol McCoy 

Credits 

Author • Katie KellerLynn

Editing • Herb Meyer and Sid Covington 

Digital Map Production • Anne Poole and Stephanie O’Meara 

Map Layout Design • Melanie Ransmeier
Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, CO 80225 

http://www.nature.nps.gov/geology/inventory/ 

(303) 969-2090 

EXPERIENCE YOUR AMERICATM 

National Park Service 

U.S. Department of the Interior