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Dinosaur track record from Late Jurassic of French Jura
From: Ben Creisler
A new online paper:
E. Cariou, N. Olivier, B. Pittet, J.-M. Mazin & P. Hantzpergue (2013)
Dinosaur track record on a shallow carbonate-dominated ramp (Loulle
section, Late Jurassic, French Jura).
Facies (advance online publication)
In 2006, sauropod and theropod trackways were discovered at the
locality of Loulle in the French Jura Mountains. During the Late
Oxfordian (sensu gallico), Loulle was located at the southeastern
margin of the carbonate-dominated French Jura platform. The upper part
of the section contains a 94-cm-thick dinosaur track-bearing interval.
Dinosaur tracks were recorded in a tidal-flat setting punctuated by
frequent flooding and emersion phases leading to desiccation,
microbial mat development, and new sediment inputs. Four types of
tracks were identified relative to their morphologies and the rheology
of the tracked sediment. Tracks were recorded on sediment with
different degrees of water saturation, covered with a thick, cohesive,
and elastic microbial mat. This mat cover prevented tracks from
erosion agents but also prevented the record of trackmaker anatomical
details. Early lithification, probably driven by enhanced
dolomitization, allowed the rapid fossilization of the tracks,
protecting them from reworking during the subsequent dinosaur tracking
phases. Sequential analysis reveals that the record of dinosaur tracks
was made possible by a gain of accommodation at the scale of
elementary (infra-Milankovitch) and small-scale (100 kyr) sequences.
The loss of accommodation observed at the scale of medium-scale (400
kyr) and very small scale (20 kyr) sequences enhanced the ramp
progradation at the Bimammatum-Planula boundary, allowing dinosaurs to
walk on the Loulle tidal-flat, along a narrow ENE/WSW isthmus.