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Sample P101A, from the Ravensthroat Formation in northwest Canada, is a laminated peloidal cap dolostone. The graded and reverse-graded peloids exhibit low-angle cross laminations easily visible to the naked eye. Peloid deposition reflects conditions in which calcium carbonate precipitation is occuring rapidly and has ...
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D-6 is a massive gray clast-rich basal tillite (diamictite) from the Storeelv glacial unit of the Ulveso Formation in eastern Greenland. The matrix is primarily composed of coarse sand. Within the sample, clast sizes range from <1 mm to 1 cm. Clast composition and size are similar to east Greenland sample #29, although...
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Sample 17 is a striated and faceted stone embedded in a sandy diamictite matrix. The erosional surfaces of the pebble suggest that it was in direct contact with mobile basal ice. The flattened (faceted) surfaces of the pebble were formed as the pebble scraped along the bedrock beneath the moving basal ice. The striatio...
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East Greenland #22 is a finely laminated buff yellow cherty carbonate mudstone (dolostone). This sample was taken from the unit that directly overlies the Storeelv formation glacial deposits. The sharpness of the contact between the Storeelv glacial succession and the overlying cap carbonate implies a rapid transition ...
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Cross-laminated sandstone composed primarily of well-rounded, coarse sand grains from the base of the Ulveso Formation. The Ulveso Formation has been interpreted as an immature aeolian deposit with a proglacial subaerial origin. This sample may have been deposited during a period of dry, windy conditions preceding the ...
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Massive clast-rich ferruginous diamictite from the Storeelv Formtion in East Greenland. The clasts are of similar composition to those in East Greenland sample D-6, but the matrix in 29 is rich in fine-grained terriginous minerals that give this basal tillite its ferrginous color. Sample is 8.5 cm across at its wi...
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Massive clast-poor diamictite from the Ulveso Formation in east Greenland. The sandy deposits in this otherwise massively bedded sample are interpreted as meltwater-washed horizons deposited in a fluctuating subglacial environment. The sandy horizon was probably originally deposited in cavities exposed by melting basal...
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- 150
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Fine-grained carbonate laminite from the Rhastoff Formation carbonates overlying Sturtian sediments in Namibia. Sample's longest dimension is 9.7 cm. This sample is from the Snowball Earth Educational Rock Sample Suite, and comes courtesy of Paul Hoffman, Harvard University; Eugene Domack, Hamilton College; and T...
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A massive clast-rich diamictite interpeted as a basal tillite deposited in direct contact with glacial ice. From the middle member of the Ghaub Formation in Namibia. Sample is 13 cm across at its widest point. This sample is from the Snowball Earth Educational Rock Sample Suite, and comes courtesy of Paul Hoffman...
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Pseudomorphosed aragonite crystal fans in calcimicrite from the Hayhook Formation. PFH-3 is an aragonite crystal fan from the Mackenzie Mountains in northwest Canada. The aragonite has been partially replaced by dolomite and calcite minerals. The sample records several intervals of fan growth and truncation, and is ...
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