TO LOG THIS EARTHCACHE INCLUDE
1. The name of this EarthCache on the first line.
2. The number of people in your group.
3. Using the Principle of Original Horizontality, has the Ione Formation undergone major tectonic change? A) Yes. The sediments are tilted more than 30 degrees from the horizontal; B) No. The sediments are still relatively horizontal; C) It is impossible to tell because the sediments do not show layering.
4. The contact between the upper gravel layer and the lower fine-grained layer is: A) an angular unconformity; B) a nonconformity; C) a disconformity.
5. Which Big Ideas (1-9) are connected (list)?
6. Which GeoPrinciples are relevant (list)?
7. Include a photo or 2 if you're so inclined (optional).
Note: In order to manage email volume, you may assume your responses are accurate if you do not get an email after logging this EarthCache. If a response is grossly inaccurate, you will not receive credit for the cache.
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GEOLOGY OF THE IONE FORMATION
Three sedimentary rock formations that crop out along the base of the Foothills in the Sierra Nevada are the Ione Formation, the Valley Springs Formation, and the Mehrten Formation (see Figure 1). Both the Ione and Valley Springs Formations are fine-grained and can look very similar. This EarthCache focuses on the Eocene Ione Formation, which is characterized by quartz-rich sandstones and kaolinitic clay deposits, including lesser amounts of conglomerates, shales, and lignite (soft brownish coal showing traces of plant structure, intermediate between bituminous coal and peat). Lindgren stated:
"During the Neocene period [the Ione was then believed to be Miocene] the auriferous gravels accumulated on the slope of the Sierra Nevada, and at the same time there was deposited in the gulf then occupying the Great Valley a sedimentary series consisting of clays and sands, to which the name Ione Formation has been given.” (Lindgren, 1894).
The Ione is likely partly “equivalent to the prevolcanic auriferous gravels of the Sierra Nevada, which occur as isolated paleochannel deposits in the lower to middle elevation of the Range” (Allen, 1929; Bateman and Wahrhaftig, 1966). Geologists generally believe the Ione and auriferous gold producing gravels are related to one another; the auriferous gravels were deposited along the upstream reaches of Tertiary rivers that eroded the ancestral Sierra (see Figures 2, 3, and 4) and the finer grained sediments made it further downstream. The Ione represents the distal (furthest downstream) deposits of these Tertiary river systems – deposits in a sedimentary basin that existed along the edge of the continent at the time. The Ione Formation has been hypothesized to have formed during Eocene time (~55-35 Ma). It is no younger than 37-40 million years old.
Figure 1: Stratigraphic Column showing the Ione, Valley Springs, and Mehrten Formations (modified from Creely and Force, 2007).
Figure 2: Map of the Ione Formation along the foothills of the Sierra Nevada from Oroville to Fresno (from Creeley and Force, 2007).
Figure 3: Map of the Ione, Mehrten, and Valley Springs Formations in Tuolumne and Calaveras Counties. Note the Ione Formation is exposed along the western edges of the counties; the Mehrten and Valley Springs Formations are exposed in the higher elevations, to the east.
Figure 4: Map of the Tertiary Mokelumne, Calaveras, Cataract Channel, and Tuolumne Rivers, and the Ione Formation in the Central Sierra Nevada. These rivers deposited gold-bearing, auriferous gravels as well as the finer-grained Ione Formation sandstone and clay deposits into the river and delta systems that emptied into a gulf along the coast of North America approximately 40 million years ago (from Lindgren, 1911).
There has been interest in the Ione Formation for its gold as well as its other resources. The auriferous gravels were well known by the miners of the gold rush and they traced these gravels uphill, if they could, hoping to locate the source of the placers. Some gold was found in the gravelly portions of the Ione. It is also still used today for its high quality clays (it is rich in kaolinite, see Figure 5), which are used in manufacturing Portland cement, pigments, and dye additives. Additionally, the lignite is a marketable fossil fuel.
Figure 5: Ione Formation near Ione, CA. Kaolinite has a low shrink–swell capacity and is a soft, earthy, usually white, mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of aluminum silicate minerals like feldspar. In many parts of the world it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield white, yellow, or light orange colors. The whitish layer in the exposure is a massive, coarse sandstone (which elsewhere in the Ione Basin has been mined for its high silica content) that represents turbulent floodplain conditions some 48 million years ago during Eocene geologic times. Above that massive white sandstone is a more thinly bedded deposit of feldspar-rich reddish-brown sandstones and shales; this, too, was likely deposited by rivers that periodically flooded their banks, but the mineral contact of the shales and sandstones is dramatically different than the essentially pure quartz content of the massive white sandstone below. The reddish-brown section contains much more feldspar and biotite, which suggests that the environment was not as humid and hot; active chemical weathering was certainly not as effective as it had been during deposition of the massive white sandstone section (from Waucob(?), 2002).
In general, the Ione Formation consists of finer grained quartz-rich sand and kaolinitic clays deposited in deltas along the coast of California, which was along the eastern Central Valley during the Eocene, approximately 40 million years ago. The climate was wetter and warmer and the rocks weathered significantly, forming the clays that are mined today, near the town of Ione. Some swamps and wetlands produced coal deposits – lignite – that is also economically marketable today.
Steno’s Principles
The Ione Formation can be partly understood by using 3 principles developed by Nicholas Steno in his work titled: “De Solido Intra Solidum Naturaliter Contento — Dissertationis Prodromus” (“Provisional Report on Solid Bodies Naturally Embedded in Other Solids”). They are:
1. Principle of Superposition
"At the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being formed, none of the upper strata existed." After observing local stream behavior, Steno concluded the oldest layers of sediments will be at the bottom of the sequence and the youngest will be on top.
2. Steno's Principle of Original Horizontality
". . . strata either perpendicular to the horizon or inclined to it, were at one time parallel to the horizon." Steno thought layers of sediment are originally deposited horizontally under the action of gravity.
3. Steno's Principle of Lateral Continuity
"Materials forming any stratum were continuous over the surface of the Earth unless some other solid bodies stood in the way." Steno believed that layers of sediment initially extend laterally in all directions (until something stops them).
For this part of the EarthCache, use Steno’s Principles to answer the following question: Has the Ione Formation undergone major tectonic change? A) Yes. The sediments are tilted more than 30 degrees from the horizontal; B) No. The sediments are still relatively horizontal; C) It is impossible to tell because the sediments do not show layering.
Unconformities
An unconformity is a buried erosional surface separating two rock layers or strata of different ages; it indicates that sediment deposition was not continuous. An interval of time elapsed between when the lower layer was deposited and the upper layer was laid down on top of it.
Angular unconformity - An unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers (see Figure 6).
Figure 6: Angular unconformity
Nonconformity - An unconformity that exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock (see Figure 7).
Figure 7: Nonconformity
Disconformity – An unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition, where there is a break in a sedimentary sequence that does not involve a difference of inclination between the strata on each side of the break (see Figure 8).
Figure 8: Disconformity
Steno’s conceptual framework led to later applications, including the first geologic map of a whole country (England) by William Smith in the late 1700’s and early 1800’s. Geologic maps are used for land use planning, hazard analysis, resource extraction, and more.
For this part of the EarthCache you will observe the outcrop at the GPS location and decide, based on your observations, what type of unconformity you are looking at. There is a gravelly layer overlying a layer of sand and clay. Look at the contact between the 2 layers. Is it: A) an angular unconformity; B) a nonconformity; or C) a disconformity? Record your answer.
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EARTH SCIENCE BIG IDEAS
The Earth Science education community put together 9 “Big Ideas” for the Earth Science Literacy Initiative (ESLI), shown below. Their purpose was to highlight the main concepts and ideas a person should understand to be literate in the earth sciences:
An Earth-science-literate person:
• understands the fundamental concepts of Earth’s many systems
• knows how to find and assess scientifically credible information about Earth
• communicates about Earth science in a meaningful way
• is able to make informed and responsible decisions regarding Earth and its resources
Which of these Big Ideas below do you think are most relevant to this EarthCache?
Earth Science Literacy Project:
1. Big Idea 1: Earth scientists use repeatable observations and testable ideas to understand and explain our planet.
2. Big Idea 2: Earth is 4.6 billion years old.
3. Big Idea 3: Earth is a complex system of interacting rock, water, air, and life.
4. Big Idea 4: Earth is continuously changing.
5. Big Idea 5: Earth is the water planet.
6. Big Idea 6: Life evolves on a dynamic Earth and continuously modifies Earth.
7. Big Idea 7: Humans depend on Earth for resources.
8. Big Idea 8: Natural Hazards pose risks to humans.
9. Big Idea 9: Humans significantly alter the Earth.
For more details see: Earth Science Literacy Initiative
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GEOPRINCIPLES
There are several fundamental principles, developed over time, that guide geological reasoning and critical thinking, listed below. Read each short description, then use your best judgement to determine which principle, or principles, best relate to this EarthCache.
7 Principles in Geology:
1. Superposition – the oldest strata are at the bottom of the sequence
2. Original Horizontality - layers of sediment are originally deposited horizontally
3. Lateral Continuity - layers of sediment initially extend laterally in all directions
4. Faunal Succession - fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances
5. Law of Intrusive Relationships - the geologic feature which cuts another is the younger of the two features
6. Uniformitarianism - the assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe
7. Catastrophism - the theory that the Earth has been affected in the past by sudden, short-lived, violent events, possibly worldwide in scope
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LOGISTICS AND SAFETY
This site is located on Camp Nine Road, near Valley Springs, Calaveras County. Please note that the road is a narrow, one lane (in many places), public road so be careful while driving and walking along the road to complete this EarthCache.
Visitors to this site should plan ahead and prepare by:
• Knowing the regulations and special concerns for the area you are planning to visit (obeying laws that prohibit collection or destruction of artifacts);
• Carrying a map and a GPS unit and/or compass;• Staying on existing roads and trails;• Staying away from any/all mine shafts and adits;
• Planning for extreme weather, hazards, and emergencies;
• Being aware that cell phones DO NOT usually work in the rural areas away from the major highways;
• Leaving your travel plans with a responsible party, including the date and time of your return;
• Being aware of any natural hazards associated with the region (e.g. poison oak, rattlesnakes, mosquitoes, cliffs/steep slopes, etc., etc);
• Carrying a full-size spare tire, extra food, water, and warm clothing;
• Following the “Tread Lightly" and "Leave No Trace” philosophy.
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TO LOG THIS EARTHCACHE INCLUDE
1. The name of this EarthCache on the first line.
2. The number of people in your group.
3. Using the Principle of Original Horizontality, has the Ione Formation undergone major tectonic change? A) Yes. The sediments are tilted more than 30 degrees from the horizontal; B) No. The sediments are still relatively horizontal; C) It is impossible to tell because the sediments do not show layering.
4. The contact between the upper gravel layer and the lower fine-grained layer is: A) an angular unconformity; B) a nonconformity; C) a disconformity.
5. Which Big Ideas (1-9) are connected (list)?
6. Which GeoPrinciples are relevant (list)?
7. Include a photo or 2 if you're so inclined (optional).
Note: In order to manage email volume, you may assume your responses are accurate if you do not get an email after logging this EarthCache. If a response is grossly inaccurate, you will not receive credit for the cache.
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Note: For a brief summary of the geologic history of the Central Sierra, see this EarthCache:
Dragoon Gulch EarthCache
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REFERENCES
1. Alden, A., March 9, 2017, “Steno's Laws or Principles”, retrieved June 27, 2017, from https://www.thoughtco.com/stenos-laws-or-principles-1440787.
2. Allen, V.T., 1929, “The lone Formation of California”: University of California, Publications in Geological Sciences, v. 18, no. 14, p. 347-448.
3. Bartow, J. Alan, 1992, “Contact Relations of the Ione and Valley Springs Formation in the east-central Great Valley, California”, Open File Report 92-588, U.S. Department of the Interior, United States Geological Survey.
4. Bateman, P.C. and Wahrhaftig, Clyde, 1966, Geology of the Sierra Nevada, in Bailey, E.H., ed., Geology of northern California: California Division of Mines and Geology Bulletin 190, p.107-172.
5. Busby, Cathy J., Andrews, G.D.M., Koerner, A.K., Brown, S.R., Melosh, B.L., and Hagan, J.C., 2016, “Progressive derangement of ancient (Mesozoic) east-west Nevadaplano paleochannels into modern (Miocene–Holocene) north-northwest trends in the Walker Lane Belt, central Sierra Nevada”, Geosphere 12, p. 135-175, 2016, http://www.geosphere.gsapubs.org.
6. Busby, Cathy J., Koerner, Alice, Hagan, Jeanette, and Andrews, Graham, 2012, “Sierra Crest graben: a Miocene Walker Lane Pull-apart in the Ancestral Cascades Arc at Sonora Pass”, in, N. Hughes and Garry Hayes (eds), “Geological Excursions, Sonora Pass Region of the Sierra Nevada”, Far Western Section, National Association of Geoscience Teachers field guide, p. 8-36.
7. Creely, Scott and Eric R. Force, 2007, “Type Region of the Ione Formation (Eocene), Central California: Stratigraphy, Paleogeography, and Relation to Auriferous Gravels”, Open-File Report 2006-1378, U.S. Department of the Interior, United States Geological Survey.
8. Earth Science Literacy Initiative (ESLI), 2010, http://www.earthscienceliteracy.org/.
9. Gamez, J., Gini, R., Fau, E., Hinch, L., Orlanda, H., 2016, “Ione Formation”, Geology 103 Sedimentology and Stratigraphy, CSU Sacramento, Professor Tim Horner, poster presented during Spring Semester 2016, http://www.csus.edu/indiv/h/hornert/geol_103_spring_2016/group%20project/ione%20poster.pdf.
10. Konigsmark, Ted, 2003, “Geologic Trips: Sierra Nevada”, GeoPress.
11. Lindgren, Waldemar, 1911, “The Tertiary Gravels of the Sierra Nevada of California”, U.S. Department of the Interior, U.S. Geological Survey, Professional Paper 73, Government Printing Office - 226 pages.
12. Putnam, Roger, (pers. comm.), June 2017, Professor of Earth Science, 11600 Columbia College Drive, Sonora, CA, 95370.
13. Rapp, John S., October 1982, “The Valley Springs Formation in the Sonora Pass Region”, Volume 35, Number 10, California Geology, California Division of Mines and Geology, p. 211-219.
14. Rohlen, G., (pers. comm.), June 2017, Teacher, Sierra Waldorf School,19234 Rawhide Rd., Jamestown, CA.
15. Schweickert, Richard, 2006, “Accretionary Tectonics of the Southern Part of the Western Sierra Nevada Metamorphic Belt” (modified from a 1999 guidebook article by Schweickert, Girty, and Hanson), in J. Tolhurst (ed), “Geology of the Central Sierra”, National Association of Geoscience Teachers Far Western Section Fall Conference field guide, p. 55-95.
16. Steno, Nicolaus, 1669, “De Solido Intra Solidum Naturaliter Contento — Dissertationis Prodromus” (“Provisional Report on Solid Bodies Naturally Embedded in Other Solids”), March 31, 2017, retrieved June 27, 2017, from http://www.worldcat.org/title/prodromus-of-nicolaus-stenos-dissertation-concerning-a-solid-body-enclosed-by-process-of-nature-within-a-solid/oclc/761328768?ht=edition&referer=di.
17. Waggoner, B. (n.d.), “Nicholas Steno (1638-1686)”, retrieved June 18, 2017, from http://www.ucmp.berkeley.edu/history/steno.html.
18. Waucob, A. (?), “The Eocene Ione Formation Project”, Field Trips to Ione Basin-October 14, 2002, retrieved June 27, 2017, from http://inyo.coffeecup.com/site/ione/fieldtrips1.html, Waucoba4@aol.com.
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