Introductory Field Trip: Lory State Park

By Jeff Neises

Image Courtesy of Courtesy of Colorado State Parks

Introduction

• I visited Lory State Park with my family quite often when I was younger. This Colorado State Park is an excellent source of recreational activities of which include hiking, rock climbing, trail running, hunting, fishing, and bicycling. We used to hike and bike on the countless trails this area has to offer to the public. When I reached high school and became interested in geological concepts Lory State Park became one of my favorite places to get away for an hour or two on the weekends. Lory State Park is an awesome area to enhance one’s learning of many important geological concepts. This area holds some of the oldest metamorphic and igneous rock formations that the Rocky Mountains have to offer. The core of the Rocky Mountains are actually composed of these same rocks. Lory State Park also holds part of the Horsetooth Reservoir. The reservoir was composed of rivers, floodplains, deserts and marine environments in past geologic periods. This has resulted in Paleozoic and Mesozoic sedimentary rocks being deposited throughout the reservoir. Over time these sedimentary rocks under went processes of tilting and uplift throughout the Lory State Park area, which has resulted in mountains being formed throughout the geologic history. Different erosion processes have produced the Lory State Park that we can observe today. Now, lets go take a look at some of the most interesting geologic points of interest the park has to offer!

Road Log• Park Office

– 708 Lodgepole Dr. Bellvue, CO 80512

– Open from 5AM-10PM daily

– lory.park@state.co.us

Directions to Lory State Park coming from Denver, CO.

Start: Merge onto I-25 N/ US-87 N. (60 miles)

Merge onto CO-14 W/ E MULBERRY ST via EXIT 269B toward FT COLLINS. (3.5 miles)

Turn SLIGHT RIGHT onto RIVERSIDE AVE. (0.6 miles)

RIVERSIDE AVE becomes JEFFERSON ST. (0.4 miles)

Turn RIGHT onto N COLLEGE AVE/ US-287 N/ CO-14 W. Continue to follow US-287 N/ CO-14 W. (3.6 miles)

Stay STRAIGHT to go onto CR-54G/ OLD US-287. Continue to follow CR-54G. (2.7 miles)

Turn LEFT onto CR-52E/ RIST CANYON RD. (0.9 miles)

Turn LEFT onto FRONT ST. (0.3 miles)

FRONT ST becomes CR-23. (1.2 miles)

Turn RIGHT onto CR-25G. (1.6 miles)

End: 708 Lodgepole Dr Bellvue, CO 80512

Trail Guide• Site 1: Arthur’s Gulch• Site 2:Fountain Formation• Site 3: Cross beds and a channel fill structure

Arthur’s Gulch

• To reach Arthur’s gulch you must hike up from the parking lot for about five minutes. This climb will take you up roughly 100 vertical feet from the base of the hiking trail. Arthur’s gulch exposes some the oldest metamorphic and igneous rocks the Rocky Mountains have to offer. These rock formations likely formed 1.7-1.8 billion years ago. Granites and Schists predominantly compose this rock formation. The core of the Rocky Mountains are actually composed of these same types of rocks. The gulch itself is an abrupt change in the topography of this area. The granite like rocks that make up this area were originally magma that cooled under the surface. The cooling of the magma was likely very deep beneath the Earth’s surface. Eventually regional metamorphism occurred, which altered the existing shale and siltstone and formed the schist formations that we observe today.

Fountain Formation

• Once arriving back to the parking lot from Arthur’s gulch, the Fountain Formation is about a fifteen minute hike at a steady pace. You will climb roughly 150 vertical feet. The source that gives the Fountain Formation its red color is Hematite. The geometry of these rocks are very interesting as well. The Fountain Formation was formed between 310-290 million years ago. Uplift of the ancient Rocky Mountains brought the granite and schist like rocks to the surface, which formed the Arthur’s Gulch rock formation. Eventually erosion of the ancient Rocky Mountains occurred, carrying different sized sediment into the nearby rivers and streams. The sediment was transported downstream and became deposited in rivers and alluvial fans. The deposited sediments eventually became lithified creating a conglomerate sandstone that composes today’s Fountain Formation. The Fountain Formation underwent various weathering reactions that released hematite (iron oxides), hence the red color we observe today.

Cross beds and a channel fill structure• From the Fountain Formation this cross

bed/channel structure is about a three minute walk. This is also about a 40 to 50 foot drop in altitude. The sedimentary cross bed is composed of sedimentary rock types including sandstone. The sediment is poorly sorted with large and small grains. There are no angular particles, big and small are rounded making this a conglomerate sandstone. This cross bed is a channel fill structure as well, which tells us that the sediment was carried down from the ancient Rocky Mountains and deposited in an alluvial fan. This created a graded bed with a layer of fine sediment on top and bottom, with coarse layer of sediment in between. Around 75 million years ago there was another occurrence of uplift within the Lory State Park region. This uplift tilted these sandstone cross beds a measurable amount, providing us with observable evidence of past geologic activity within the region.

Wrapping it all up

• After you have now traveled through Lory State Park it is important to remember that you have experienced roughly 1.7 billion years of geologic events. This is the place where I first became interested in geological concepts. I can only hope that Lory State Park has the same affect on you. Now go ahead dive in, this area has more than enough outdoor recreational activities for one to find something they enjoy doing. Whether it be hiking, biking, rock climbing, swimming, hunting, site-seeing, or another activity of your choice I would highly recommend this area to anyone who enjoys the visualizing the history of our planet!

Sources

• No Author Listed. Lory State Park. Colorado State Parks [Internet]. 2008 [Cited: 4/6/08]. Available from: http://parks.state.co.us/Parks/lory.

• No Author Listed. Lory State. Park. State Parks [Internet]. 2008 [Cited: 4/7/08]. Available from: http://www.stateparks.com/lory.html

• Warnock, A.; Rathburn, S.; Thompson, S. Geology of Lory State Park, Colorado. Estes Park, CO: Rocky Mountain Nature Association, 2004.