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Cannibalism
Cannibalism exhibited by the fish Dastilbe crandalli, Cretaceous Crato Fm., Brazil. Specimen on display at the Paleontological Museum in Santana do Cariri. Larger fish is about 10 cm in size. Unique environmental conditions are required for such spectacular preservation of fossil fish. This form of cannibalism is also interpreted as indicative of stressful environmental conditions.
Rt34
IGNEOUS - INTRUSIVE: Potassium feldspar, Big Thompson Canyon --- The potassium in this mineral is often used in K-Ar (potassium-argon) radiometric dating.
Volcanic cone
View of Bartolomé Island, where a parasitic cone is observed on the right side of the photograph. Notice the reddish colors from weathering of the volcanic rocks.
Current ripples
Walking on water? Not really, but these ripples, now petrified, formed under shallow water and are exposed on the floor of a quarry at the Varvito Park, Ito, Brazil. They are part of exposures of Permian sandstone from the Itararé Group. The ripple crests are mostly linear and the profile of the ripple is asymmetric, allowing to reconstruct the direction of flow (towards the viewer).
Dinosaur trackways
Dinosaur trackways, the main one thought to have been left by an ankylosaurid (hammer for scale). Cretaceous El Molino Fm., Torotoro, Bolivia. Well developed fossil trackways imply a special set of conditions, with sediment wet enough for footprints to remain impressed followed by prompt induration and burial.
Basalt Cliffs
IGNEOUS - EXTRUSIVE: Basalt cliffs, Grand Mesa --- Tertiary basalt flowed down a valley and hardened. Later erosion formed these cliffs where the hard basalt caps the mesa. Grand Mesa is an inverted valley -- what was low has now become high.
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 the Varvito Park, Ito, Brazil, with exposures of Permian strata from the Itararé Group. Scale in cm.
Shellbed
Accumulations of skeletal fragments of marine invertebrates are common in the geologic record and are important for reconstruction of depositional processes. This is a Permian example from the Copacabana Fm. of Bolivia, dominated by brachiopods (including Neospirifer condor) and crinoids.
Rt 34
IGNEOUS - EXTRUSIVE: Volcanic tuff layers, Rt.34 near Grand Lake --- This volcanic ash was deposited in the Tertiary.
Climbing ripples
When a fluid laden with sediment rapidly drops some of its load as it is flowing, a sedimentary structure named "climbing ripple lamination" can form. It is characterized by superimposed ripple crests (or ripple cross-sets) migrating in the direction of flow. Photo taken at the Varvito Park, Ito, Brazil, with exposures of Permian strata from the Itararé Group. Scale in cm.
Bioturbation
The distinctive linear patterns observed on the surface of this sandstone bed are trace fossils produced by crustaceans as they were moving in the originally loose sediment. The technical term for this type of biogenic structures is bioturbation. Photo taken on a sandstone slab at the Varvito Park, Ito, Brazil, with exposures of Permian strata from the Itararé Group.