«Guidebook to the Geology of Quarry Park Waite Park, MN Shawn W. West Department of Earth and Atmospheric Sciences St. Cloud State University May 4th ...»
Guidebook to the Geology of Quarry Park
Waite Park, MN
Shawn W. West
Department of Earth and Atmospheric Sciences
St. Cloud State University
May 4th 2012
(Dr. Kate Pound, Advisor) __________________
(Dr. Adrian Van Rythoven, Reader) __________________
(Mike Totenhagen, Reader) ___________________
I would like to personally thank everybody that provided guidance and support during
my research and time at St. Cloud State University. Special thanks to Dr. Kate Pound, my advisor, Chuck Wocken and the Quarry Park staff. Thanks also to the Geography Department for the use of student copies of Arc GI. Dr. Adrian Van Rythoven and Mike Totenhagen provided review of my research and also for being good friends and colleagues. I would like to acknowledge all the geologists and earth scientists who have contributed to the understanding of St. Cloud’s regional geology.
Discussion on Background Information and History of Quarry Park Abstract Quarry Park and Nature preserve is located south of the city of Waite Park, a suburb of St. Cloud, off of county road 137. The park encompasses six hundred eighty four acres of forest and wetlands. Quarry Park provides many year round activities such as fishing, swimming, and rock climbing and snowshoeing. Many outdoor enthusiasts and nature lovers flock to the park year round. The goal of my research is to provide a user- friendly field guide to a sometimes forgotten asset of Quarry Park. The geology! It will take approximately two hours to visit all the sites listed in the field guide. The user can decide on which stops they wish to visit. The first part of this field guide provides background on the general geology of the region; I would recommend reading the report first before using the field guide.
History The quarries for which Quarry Park was named, began in the late 1800’s with the mining of the St. Cloud granite and the Reformatory granite. These granite’s, when polished have a beautiful red or grey finish with visible large crystals. These crystals include plagioclase, microcline, quartz and biotite. These types of dimension stone were heavily sought after and had many applications as building materials. Through the early 1900’s St. Cloud and Reformatory granites were used for exterior decoration on the outside of many buildings throughout the country. The quarrying of dimension stone within Quarry Park stopped in the 1950’s. The land on which Quarry Park sits was sold by the Cold Spring Granite Company in 1992 to Stearns County. Since 1992 to the present Quarry Park has been allowed to return to its natural roots, thus the classification of Quarry Park as a Nature Preserve. Granite is still mined in the area, mostly for aggregate uses, but not within the preserve.
Geologic Historyof the Region There have been many important geologic events that have shaped the landscape of eastern Stearns County. Two billion years ago there was a shallow sea way covering what is now the state of Minnesota. Shallow seas are favorable for creating sedimentary rock types such as limestone, sandstone and shale. “The metamorphic rock to the north and west would constitute the cratonic margin along which an active subduction zone produced the Penokean Orogeny”. (Boerboom, et al, 2011). At around 1.9 billion years ago a mountain building event called the Penokean Orogeny began. The collision of two continents caused the crust to thicken. The forces causing the thickening crust would have created greater temperatures at depth melting the rocks. This molten rock would eventually cool and create the granites located within Quarry Park and throughout the region. These igneous rocks when cooled relatively slowly at depth are called plutons.
Figure 1: A) This figure is a representation of a subduction zone similar to what existed before two billion years ago. The ocean crust is more dense compared to continental crust and is forced under the continental crust. The crust is then melted, these melts under great pressure and heat make their way back into the crust through fractures and faults forming intrusions B) Figure B represents an orogenic event similar to the Penokean Orogeny. The collision of an island arc and continental plate produces thickening of the crust and magmatic intrusions similar to the St.
Cloud and Reformatory Granites. http://slohs.slcusd.org/pages/teachers/rhamley/Biology/Continental%20Drift/Tectonics.html At around 1.1 billion years ago, an ocean-forming event called the Keewenawan Rift began to develop. This rifting event was caused by the “thinning” of the crust. Here thinning of the crust is caused by convection forces within the mantle with magma upwelling to the crust from the mantle and/or crust below. The thinning of the crust allowed for the release of pressure and magmatic fluids from within the lower part of the crust. This magma would cool and form the mafic and felsic intrusions throughout the region. The Keewenawan Rift System eventually failed, with rifting only partially completed. Over the next 990 million years a series of depositional and erosional environments would sculpt the land scape. Many of these sedimentary units can still be seen throughout southern Minnesota and Wisconsin.
Figure 2: Diagram showing the extent and volcanic/elastic rocks of the keewenawan Rift Sequence.
https://sites.google.com/a/stumail.hopkins.k12.mn.us/mn-geology/home/map The most recent important geological event in this region is the glaciation of North America. The last major glacial advance and retreat occurred around ten thousand years ago.
The ice removed the sedimentary rock deposited by the earlier shallow seas exposing the igneous bedrock below. The ice left visible evidence behind in a series of landforms of eroded material called eskers and drumlins. Many of these ice features today are mined for gravel and other aggregate operations throughout the upper Midwest. More evidence for the advance and retreat of ice comes in the form of scratches or striations exposed on bedrock throughout Quarry Park. These striations tend to be all parallel to one another and show the direction of movement of the ice. Other ice evidence in the form of chatter marks and rouche moutonee structures can also be seen.
Figure 3: This figure shows the extent of glaciation in the upper Midwest.
Geology of Quarry Park There are four major rock types that make up the geology of Quarry Park. The oldest rock type within the park is called the Reformatory Granite with a, “reported U-Pb age of 1,812 Ma” (Boerboom & Holm, 2000). This 1.8 billion year age correlates well with the Penokean Orogeny. The Reformatory Granite is a “dark gray to pinkish gray medium-grained, weakly porphyritic biotite-hornblende granodiorite.” (Boerboom & Holm, 2000). The major minerals that make up this granite are oligoclase (grey to white feldspar), quartz, biotite and hornblende.
There are occasional phenocrysts (larger crystals) of potassium feldspars which give some of the pink color to the usually grey granite.
The second oldest rock within Quarry Park is the St. Cloud Granite. This granite has a “uranium-lead age date of approximately 1.77 billion years” (Boerboom & Holm 2000). The St.
Cloud Granite is a “coarse-grained, dusky red-colored hornblende granite, with a distinctive mottled pink and black color” (Boerboom & Holm, 2000). The major minerals that make up the composition of the St. Cloud granite are potassium feldspar (microcline), quartz, hornblende and biotite. Because of the beautiful red color, the St. Cloud Granite was extensively quarried throughout the park and makes up most of the “outcrops” on the east and west sides of the park. According to research done by George W. Shurr and Garry G. Anderson in 1995, the St.
Cloud Granites on the both sides of the park have distinct differences in grain size, mineralogy and magnetic signatures. Because the St. Cloud granite intruded the Reformatory Granite, small pieces or xenoliths of Reformatory can be found within the St. Cloud Granite. These xenoliths are formed when the St. Cloud granite intruded the Reformatory granite and simply broke off pieces and entrained them within the magma.
The next oldest rocks within the nature preserve are diabase (mafic) dikes. We will break these dikes into two categories, northwest and northeast trending. According to Boerboom and Holm (2000), “these dikes are the youngest Precambrian rocks within Stearns County.” With an age of approximately 1.1 billion years these mafic dikes would have intruded the Reformatory and St. Cloud granites through weaknesses such as faults, fractures and contacts. The northwest trending mafic dikes can have a width up to 100 meters and are not well exposed at the surface. The northwest trending dikes do have greater amounts of magnetic minerals (magnetite and pyrrhotite); therefore geophysical methods such as aeromagnetics help to define these dikes in the subsurface. The northeast trending diabase dikes are abundant throughout Quarry Park. They tend to have fine to medium grain sizes with very small chill margins. These margins may also be marked by minor amounts of cryptocrystalline quartz and chlorite.
Figure 4: This photo shows the contact between a northeast trending diabase or mafic dike and the St. Cloud Granite.
The final rock type within Quarry Park is minor yet unique. Boerboom and Holm (2000) refer to this dike as microgranite porphyry. Throughout the area these dikes intrude the Reformatory and St. Cloud granites and are also found intruding the center of a diabase dike located in an active quarry outside the nature preserve. “The microgranite dikes have strongly chilled, locally flow-banded margins, and are texturally similar to volcanic rhyolite” (Boerboom & Holm 2000). The microgranite contains phenocrysts of microperthite and quartz within a fine ground mass of feldspar and quartz with biotite and hornblende. The location and timing of these dikes tends to coincide with the emplacement of the diabase dikes and likely used the same fractures within the rock during the Keewenawan Rift Sequence. The specific age of the microgranite porphyry is not yet known, and there is still speculation on the age of these dikes based on field relationships.
There is one minor igneous rock type within the park called aplite. It is thought to be associated with the St. Cloud Granite and shares similar mineralogy with the St. Cloud Granite.
Aplite bodies are thought to be to be a good indicator of Reformatory Granite because of the spatial relationship between the two. Aplite has a sugary texture and is generally aphanitic.
Figure 5: Hand Samples from Quarry Park The Field Guide to the Geology of Quarry Park There are a total of thirteen different stops included in this field guide. All stops represent interesting points of geology within the park. Each point is marked with an orange dot on the map below. These dots correlate to a GPS point taken in the field. Keep in mind there is a three to twelve meter error when using a GPS. Make sure your unit is set to UTM coordinates using the WGS 1984 datum when finding the stops within the field guide. You will also have to set up your unit to the correct zone (15T).
Figure 6: Map of Quarry Park with trails, quarries and field guide stops highlighted. The parking lot and county road 137 is located in the upper left hand corner. Field guide stops are orange dots with a corresponding yellow number.
Figure 7: Geological map with trails, quarries and field stops featured. Notice how the Reformatory Granite located in the middle of the park is flanked on the east and west sides by the St. Cloud Granite. This generalized geological map. The intrusive relationships between St. Cloud and Reformatory granite are very complex and cannot be shown on this scale of map.
Stop 1: The Dimension Stone Yard.
Easting: 403077 Northing: 5043093 The dimension stone yard is located just inside the park south of the parking lot. It is important to understand the history and culture that influenced the quarrying of dimension stone within the park. Here you have a chance to see the tools and equipment used in the quarrying process.
Figure 8: Geological Map showing the northwest corner of the park, including parking lot and quarries 13-20.
Figure 9: Dimension stone yard, Quarry Park and Nature Preserve. View looking to the southwest.
Stop 2: Diabase Dikes Located Near Quarries 18 and 19.
UTM Easting: 403047 Northing: 5043048 Stop two is located next to the dimension stone yard and close to stop number one. From here, you can see and measure the strike and dip of three diabase dikes, the first striking roughly 90 degrees and dipping at a steep angle of 65 degrees south. The second dike trends roughly 90 and is vertical. The third dike strikes 65 degrees and dips 75 degrees to the south. All three dikes intrude the St. Cloud Granite
Figure 10: Geological map of stops 1-4, along with locations of field guide stops.
Figures 11 & 12: 11) Diabase (basalt) dikes intruding St. Cloud granite at field guide stop 2. Both dikes strike roughly 90 degrees, the one in the center of the photo has a vertical dip, the dike to the right side of the photo has a dip of 65 degrees south. 12) Diabase dike with a trend of 65 and a dip of 75 degrees south.
Stop 3: Diabase Dike with Possible Reformatory Granite Xenolith and Aplite Body.
UTM Easting: 403001 Northing: 5043013 Stop 3 is interesting because you can stand right on a series of diabase “dikelets”. These dikes are only one to three inches wide and are relatively close in proximity to the dikes viewed at stop two. These dikelits intrude an aplite body and the contact between the St. Cloud granite and the Reformatory granite. The aplite body is very fine grained and has a sugary texture.
“Most aplite bodies are found within the grey Reformatory Granite.”(Shurr & Anderson 1995).
Figure 13: Diabase Dikelets within Reformatory Granite. The right side of the photo shows the aplite body, fine grained pinkish mass with definite boundary and change in texture. The diabase dikes intrude and cross the aplite body and Reformatory Granite.
Stop 4: Wide Diabase Dikes Intruding St. Cloud Granite at Quarry 13.