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Asymmetric ripples
Current ripples are small asymmetric bedforms generated by movement of fine-grained sediment under unidirectional currents. The presence of climbing ripple lamination indicates rapid deposition from a sediment-laden flow. Upward transition from planar lamination to current ripple lamination is indicative of flow deceleration. Sequence of sedimentary structures (cf. Bouma sequence), grain size decrease, and cyclical repetition of bedding points to deposition from turbidity currents. Photo taken at…
Dropstone
Dropstones are outsized rock clasts much larger than the average grain size of the surrounding sediment. Rather than being laterally transported by a flow, they show evidence (in the form of displacement of underlying lamination) of vertical sinking onto the substrate. The dropstone in the picture has a diameter of about 20 cm and is included in turbiditic deposits (Permian Itararé Group, Itu, Brazil).
Punta Grohmann section
The iconic Punta Grohmann section, in the Dolomites of Italy, showcases Triassic (Ladinian to Carnian) basinal deposits visible in the grassy slopes at the center of the photo, overlain by the towering dolomitized limestone of the Cassian Dolomite Formation. The basinal deposits accumulated in troughs between carbonate platforms and preserve evidence of catastrophic processes, including volcanism, turbidity currents, and toe-of-slope deposits containing large limestone blocks that collapsed from…