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Depositional setting and early diagenesis of the dinosaur eggshell-bearing Aren Fm at Bastus, Late Campanian, south-central Pyrenees

Díaz Molina, Margarita and Kälin, Otto and Benito Moreno, María Isabel and López Martínez, Nieves and Vicens, Enric (2007) Depositional setting and early diagenesis of the dinosaur eggshell-bearing Aren Fm at Bastus, Late Campanian, south-central Pyrenees. Sedimentary Geology, 199 . pp. 205-221. ISSN 0037-0738


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The Late Cretaceous Aren Fm exposed north of Bastus in the Tremp Basin (south-central Pyrenees) preserves an excellent record
of dinosaur eggs laid in a marine littoral setting. Different from other cases reported in literature, at the Bastus site the preferential
nesting ground was original beach sand. The coastal deposits of Aren Fm can be grouped into four facies assemblages, representing
respectively shoreface, beachface, beach ridge plain and backbarrier lagoon environments. Shoreface deposits include fine- to coarsegrained
hybrid arenites and subordinate quartz-dominated conglomerates with ripple structures of wave and wave-current origin.
Beachface deposits are mainly storm beach conglomerates, but parallel-laminated foreshore arenites locally occur. Backbarrier lagoon
deposits comprise of washover sandy conglomerates that grade laterally into sandy lime mudstones, biomicrites and marls.
Beach ridge sediment, wherein the bulk of dinosaur eggs and eggshell debris occurs, predominantly is a reddish hybrid arenite
that has undergone a complex early diagenetic evolution, including marine and meteoric cementation followed by soil
development. The reddish arenites overlie wave-dominated shoreface deposits and in places pass laterally into lagoonal deposits.
They originally formed shore ridges, that became stabilized during progradational episodes by pedogenesis (beach ridge, sensu
[Otvos, E.G., 2000. Beach ridges—definitions and significance. Geomorphology 32, 83–108.]), which also affected the dinosaur
eggs. The eggshell-bearing beach ridge arenites are typically preserved at the top of parasequences forming the systems tracts of a
third-order sequence. Thick packages of this facies resulted from aggradation of barrier/beach ridge deposits, whose preservation
below surfaces of transgressive erosion was favoured by incipient lithification.

Item Type:Article
Uncontrolled Keywords:Paleoenvironments; Beach ridges; Dinosaur eggs; Diagenesis; Cretaceous
Subjects:Sciences > Geology > Paleontology
Sciences > Geology > Stratigraphic geology
ID Code:10527
Deposited On:26 Apr 2010 10:51
Last Modified:06 Feb 2014 08:44

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