New Maastrichtian Cretaceous Tidal Deposits Found in Madagascar, Contains Dinosaur, Mammals Fossils

A new, richly fossiliferous member comprised of tidal deposits in the Upper Cretaceous Maevarano Formation, northwestern Madagascar

Authors:

1. Raymond R. Rogers (a)
2. David W. Krause (b)
3. Sophia C. Kast (a)
4. Madeline S. Marshall (a, c)
5. Lydia Rahantarisoa (d)
6. Colin R. Robins (e)
7. Joseph J.W. Sertich (f)

Affiliations:

a. Geology Department, Macalester College, Saint Paul, MN 55105, USA

b. Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794, USA

c. Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA

d. Département de Paléontologie, Université d'Antananarivo, Antananarivo (101), Madagascar

e. W.M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, CA 91711, USA

f. Department of Earth Sciences, Denver Museum of Nature and Science, Denver, CO 80205, USA

Abstract:

A new member of the Upper Cretaceous (Maastrichtian) Maevarano Formation is proposed to accommodate a distinctive succession of strata exposed along the shores of Lac Kinkony in northwestern Madagascar. The new Lac Kinkony Member overlies fully terrestrial sandstones of the Anembalemba Member of the Maevarano Formation, and is capped by marine dolostones of the Berivotra Formation. In the stratotype section, the base of the Lac Kinkony Member consists of siltstone interbeds that host networks of Ophiomorpha. Siltstone facies pass up-section to distinctive white sandstones packed with dolomitic mud matrix that exhibit rhythmic clay drapes, flaser and wavy bedding, and oppositely-oriented ripples developed on the toes of larger foresets. Thin flat interbeds of microgranular dolostone and claystone comprise the uppermost facies of the Lac Kinkony Member, and a laterally traceable ravinement bed mantled by cobbles of rounded dolostone marks the contact with the superjacent Berivotra Formation. Deposits of the Lac Kinkony Member are interpreted to represent siliciclastic and carbonate tidal flats dissected by tidally-influenced rivers. Vertebrate fossils are abundantly preserved in these coastal deposits, and are locally concentrated in microfossil bonebeds that have the potential to yield thousands of small identifiable specimens. In addition to many taxa already known from the Maevarano Formation, the Lac Kinkony Member has yielded a wealth of phyllodontid albuloid fish skull elements, the distal humerus of a new frog taxon, five vertebrae representing two new snakes, a tooth of a possible dromaeosaurid, and a complete skull of a new mammal. The discovery of several new vertebrate taxa from this new member reflects the fact that it samples a previously unsampled nearshore, peritidal paleoenvironment in the Late Cretaceous of Madagascar.

The mammal skull is exciting.