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Late Cretaceous/early Cenozoic land bridges in Northern Hemisphere (free pdf)



From: Ben Creisler
bcreisler@gmail.com

A new paper in open access that may be of interest:

Leonidas Brikiatis (2014)
The De Geer, Thulean and Beringia routes: key concepts for
understanding early Cenozoic biogeography.
Journal of Biogeography (advance online publication)
DOI: 10.1111/jbi.12310
http://onlinelibrary.wiley.com/doi/10.1111/jbi.12310/abstract

Abstract
Aim
I re-evaluate the specific biogeographical significance of each of the
land bridges (Beringia, Thulean and De Geer) in the Northern
Hemisphere during the latest Cretaceous-early Cenozoic, showing that
the Thulean and De Geer routes did not operate contemporaneously.

Location
Northern Hemisphere landmasses.

Methods
I review the recent climatic, sea-level, geotectonic, palaeofloristic,
and marine and terrestrial faunal data that have emerged since the
establishment in the 1980s of the biogeographical concepts of the
early Cenozoic Northern Hemisphere land bridges and present a
synthesis supporting a revised scenario for early Cenozoic
biogeographical development.

Results
Palaeogeographical and geotectonic data, supported by strong floral
and faunal evidence, suggest that the palaeogeographical and
chronological frames for the formation of all three land bridges are
different from those originally proposed. Dispersal events via the
causeways seem to have taken place during specific time intervals
resulting from fluctuations in sea level and climate.

Main conclusions
The De Geer and Thulean routes were not contemporaneous. The former
existed during the latest Cretaceous to the early Palaeocene, joining
North America with Eurasia. The Thulean route became established well
after the interruption of the De Geer route, offering a southerly
connection between western Europe and North America in at least two
episodes: c. 57 Ma and c. 56 Ma. The Bering route functioned in two
warm periods: 65.5 Ma (coinciding with the De Geer route) and c. 58
Ma, during the Palaeocene (possible Eocene exposures are not
considered here). The formation of the De Geer route explains faunal
similarities between the Puercan and Torrejonian North American land
mammal ages (NALMAs) and the Shanghuan Asian land mammal age (ALMA).
The Thulean route explains faunal similarities between the
Clarkforkian (Cf1) and Wasatchian (Wa0, 1) NALMAs, and the Cernaysian
and Neustrian (PE I, II) European land mammal ages. The Bering route
explains faunal similarities between the Gashatan ALMA and the
Tiffanian (Ti5) NALMA.
**

Keywords:

Arctic palaeogeography;Barents Sea;Beringia;De Geer route;land mammal
ages;Maastrichtian climate;New Jersey sea-level;North Atlantic
land-bridges;Palaeocene climate;Thulean land-bridge