Snowball Earth Educational Rock Sample Suite 36 by Robin Rohrback-Schiavone

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 growth of a continental ice sheet. As ice accumulated, marine margin facies became remobilized and were deposited farther down the continental slope by the onset of glacial ice.

Sample is 5 cm across at its widest point.

This sample is from the Snowball Earth Educational Rock Sample Suite, and comes courtesy of Paul Hoffman, Harvard University; Eugene Domack, Hamilton College; and Timothy Fox, Hamilton College.
For more information on the Snowball Earth Educational Rock Sample Suite, visit www.snowballearth.org/samples.html 
Image made as part of the MAGIC project (Mid-Atlantic Geo-Imagery Collection) using Northern Virginia Community College's gigamacro rig, as seen here:
gigamacro.com/gigapixel-macro-imaging-system /