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Ichthyosaur graveyard from Lower Cretaceous in Chile



From: Ben Creisler
bcreisler@gmail.com

A recent paper not yet mentioned:


Wolfgang Stinnesbeck, Eberhard Frey, Luis Rivas, Judith Pardo Pérez,
Marcelo Leppe Cartes, Christian Salazar Soto and Patricio Zambrano
Lobos (2014)
A Lower Cretaceous ichthyosaur graveyard in deep marine slope channel
deposits at Torres del Paine National Park, southern Chile.
Geological Society of America Bulletin (advance online publication)
doi: 10.1130/B30964.1
http://bulletin.geoscienceworld.org/content/early/2014/05/22/B30964.1.abstract?sid=dd9a224c-919f-4030-a4a6-afae70881930

Remnants of ophthalmosaurid ichthyosaurs recently discovered in the
vicinity of the Tyndall Glacier in the Torres del Paine National Park
of southern Chile are extremely abundant and well preserved. After
three field campaigns to the area, a total of 46 articulated and
virtually complete ichthyosaur specimens, both adults and juveniles,
were tentatively assigned to four different species of
Ophthalmosauridae. Preservation is excellent and occasionally includes
soft tissue and embryos. The skeletons are associated with ammonites,
belemnites, inoceramid bivalves, and fishes as well as numerous plant
remains. The enormous concentration of ichthyosaurs is unique for
Chile and South America and places the Tyndall locality among the
prime fossil Lagerstätten for Early Cretaceous marine reptiles
worldwide.

The deposit is Early Cretaceous (Valanginian–Hauterivian) in age and
forms part of a monotonous bathyal to abyssal sequence of the Late
Jurassic to late Early Cretaceous Rocas Verdes back-arc basin. In this
region, the Tyndall ichthyosaur population may have profited from cold
upwelling currents that caused abundant life at the shelf edge
including masses of belemnites and small fish, the preferred diet of
ichthyosaurs. The abundance of almost completely articulated
ichthyosaur skeletons in the Tyndall area suggests that some animals
fell victim to episodic mass-mortality events caused by turbidity
currents traveling downslope through a submarine canyon. They lost
orientation, drowned, and were dragged into the deep sea by these
turbulent high-energy gravity flows. Their bodies ended up in an
oxygen-deficient basin environment where they were immediately
embedded by the fine turbidite suspension fallout. The Tyndall
ichthyosaur locality thus combines characteristics of both
concentration and conservation Lagerstätten.