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2 years ago in Earth Sciences , Sedimentology By Larry
Are these ice-keel marks?
I'm describing a Carboniferous succession in the Paraná Basin with beautiful, thin-bedded rhythmites. On certain bedding planes, I'm seeing parallel, straight to slightly curved grooves and ridges, several meters long. The context suggests a glacial marine environment. Before I confidently label them as ice-keel marks in my publication, what are the definitive criteria to distinguish them from other groove-forming processes like subaqueous mass wasting or tectonic slickensides?
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By Henry Answered 7 months ago
This is a classic interpretive challenge. From my work on Pleistocene glacial lakes, true ice-keel scours have a specific signature. Look for a triangular to V-shaped cross-section in perpendicular view, often with a raised berm of deformed sediment (push-up) along the sides. The grooves should be isolated or in sub-parallel sets, not forming interconnected networks like mudcracks. Critically, they will cross-cut other soft-sediment features (like small faults or ripples) without offsetting them, proving they were formed on an exposed, soft seafloor. If you see tool marks (smaller scratches within the groove) or a consistent orientation across a wide area, that strongly supports drifting icebergs, not localized slumping.
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