Welcome to my Earthcache! An Earthcache is a special type of geocache where there is no container to find - instead you are looking for a unique geological feature of the area and need to answer questions, as well as posting a picture, in order to claim the find. As you paddle along the Grand River near Onondaga, this earthcache will require you to visit three unique sites and compare the glacial till at this three locations, determining what type of glacial till you believe is here based on your observations and the chart below. Each type of glacial till within the Grand River Watershed is unique - this earthcache explores several of the different types of glacial till in the area including their features.
Please note: You will need a boat of some sort to access GZ, as walking in from thr roas would be dangerous, and result in trespassing. You will need to put in at one of the waypointed boat launches, and paddle (motorized vessels are also permitted here) to the coordinates to make your observations. Please make sure you are staying safe while doing this - bring all of the legally required safety gear with you, and make sure you paddle according to weather and water conditions. It will not be possible to complete this earthcache in the winter or during the spring floods.
This is a 5/5 earthcache It is not a park and grab. Expect to take up to an hour to record your oberservations properly and answer the questions. As with all of my ECs, I am not looking for PhD thesis level responses, but I am hoping that you take some time to enjoy the area and learn something new. Please include a list of all cachers with your answer, if answering for more than one caching name.
To claim a 'find' for this Earthcache you must answer the following questions and send your answers in a message or email to the owner using the link at the top of the page. You can log your find with a photo at GZ. Send your answers to the tasks. I will be in contact if there is a problem, no need to wait for a response as long as the required photo is included in your log.
Questions to Answer:
1. Posted Coordinates - Describe the material you see. Is it made up of mostly fine-grained clay/silt or is it more sandy/stony? What colors do you observe? Is the material well mixed or layered and stratisfied (sorted according to material)? Can you see distinct layers or changes in composition, or is everything all mixed together? How does it change from the top of the bank to the bottom of the bank/under water? Is the till very firm and compact, or crumbly and loose? Does it seem to retain moisture (clayey), or is it well-drained (sandy)?
2. Stage 2 - Describe the material you see. Is it made up of mostly fine-grained clay/silt or is it more sandy/stony? What colors do you observe? Is the material well mixed or layered and stratisfied (sorted according to material)? Can you see distinct layers or changes in composition, or is everything all mixed together? How does it change from the top of the bank to the bottom of the bank/under water? Is the till very firm and compact, or crumbly and loose? Does it seem to retain moisture (clayey), or is it well-drained (sandy)?
3. Stage 3 - Describe the material you see. Is it made up of mostly fine-grained clay/silt or is it more sandy/stony? What colors do you observe? Is the material well mixed or layered and stratisfied (sorted according to material)? Can you see distinct layers or changes in composition, or is everything all mixed together? How does it change from the top of the bank to the bottom of the bank/under water? Is the till very firm and compact, or crumbly and loose? Does it seem to retain moisture (clayey), or is it well-drained (sandy)?
4. Compare the three locations - Using the chart below, explain which type(s) of glacial till you see at each stage, and explain your reasoning.
5. Photo Requirement: Take a photo of yourself (or just your GPS device, or your geocaching name on a piece of paper, or your signature item, a thumbs up) with the clay banks in the background. You are not required to show your face in the photo, but each geocacher should upload an image with their log indicating that they were there. You are also welcome to share other photos of your visit to this beautiful area, but at least once image should show you with the clay visible in the background.
Earthcache lesson:
The Grand River watershed, stretching from Dundalk in the north to Lake Erie in the south, is a rich geological archive of repeated glaciation. Much of its modern topography—rolling hills, river valleys, and fertile plains—owes its shape and soil composition to a complex sequence of glacial till deposits. These deposits are not random; they are organized in stratified layers that reflect successive advances and retreats of massive ice sheets over tens of thousands of years.
Each time a glacier advanced into this region, it scraped up rock and sediment from the landscape and carried it along, depositing the material directly beneath and around the ice. The result is glacial till, a poorly sorted mix of clay, silt, sand, gravel, and stones. Unlike river sediments, which tend to sort themselves into layers, glacial till is typically chaotic in composition—a jumbled snapshot of the material gathered by the glacier.
In the Grand River watershed, geologists have identified over a dozen distinct till units, each with unique characteristics such as texture, color, degree of compaction, and mineral composition. These differences are due to the varying conditions under which each till was deposited—differences in ice origin, sediment supply, temperature, and even the presence of glacial lakes and meltwater.
What is Glacial Till?
Glacial till is:
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Diamicton: a poorly sorted sediment containing a wide range of particle sizes.
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Unstratified: lacking layers due to direct deposition from melting ice.
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Highly variable: texture and color change depending on ice source and depositional conditions.
In the Grand River region, geologists have identified at least 12 major till units, each with distinct textures and histories.
Major Glacial Till Units in the Grand River Watershed
| Till Unit |
Age / Position |
Description |
Key Features |
| Halton Till |
Youngest |
Clayey, stone-poor diamicton, sometimes with glaciolacustrine clay and debris flows |
Dense, grey to brown, poorly drained; may contain lakebed sediments |
| Wentworth Till |
Late Wisconsin |
Stony silty sand to sandy diamicton with beds of sand and gravel |
Coarser texture, well-drained, evidence of energetic meltwater deposition |
| Stratford Till |
Wisconsin |
Silty to clayey, locally sandy diamicton |
Moderately compact, often brown-grey; transitional texture |
| Mornington Till |
Wisconsin |
Silty to clayey, with stone-poor, laminated clayey silt |
Laminated structure; may show signs of glaciolacustrine influence |
| Port Stanley Till |
Wisconsin |
Fissile, stony silty sand diamicton with clayey variations |
Brittle layers; sandy texture; can be compact and stony |
| Tavistock Till |
Wisconsin |
Clayey silt to sandy silt diamicton, often laminated |
Layered appearance, variable compaction; intermediate in grain size |
| Stirton Till |
Wisconsin |
Sandy silt to silty clay diamicton |
Finer-grained than Wentworth; typically massive (non-layered) |
| Maryhill Till |
Wisconsin |
Bedded silt and clay, with silty diamicton layers |
Rhythmically layered; acts as an aquitard; important for groundwater modeling |
| Catfish Creek Till |
Early Wisconsin |
Overconsolidated stony sandy silt diamicton with deformed laminations |
Very hard, compact; highly deformed; may contain sand/gravel beds |
| Canning Till |
Illinoian or older |
Reddish to mauve-grey, stone-poor silty diamicton with fine interbedding |
Distinctive red color; oxidized; exposed at select riverbanks like the Nith River |
These tills are more than just dirt—they're clues. Their layering, structure, and contents help scientists determine:
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The direction of past ice flows
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The timing and extent of glacial events
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Paleoenvironments such as glacial lakes and interglacial wetlands
Understanding glacial till also has practical applications. Certain tills act as aquitards, limiting the movement of groundwater and influencing well placement and aquifer recharge. Others form the foundation of soils that support agriculture, forestry, and development.
This EarthCache invites you to examine a till exposure and use your observational skills to interpret its origin. Are you looking at a quiet, clay-rich deposit left under a stagnant ice sheet—or a chaotic, gravelly mixture laid down by fast-moving meltwater? By recognizing the clues in glacial till, you're reading a chapter from Ontario’s deep geological past.
References:
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Grand River Conservation Authority (2019). Watershed Geology Overview.
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Burt, A. (2014, 2017); Bajc, A. & Shirota, J. (2007); Singer, S.N. et al. (2003)
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Ontario Geological Survey Quaternary Mapping Series