GLORIA

GEOMAR Library Ocean Research Information Access

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 2015-2019  (2)
  • 1
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science Advances 2 (2016): e1600883, doi:10.1126/sciadv.1600883.
    Description: The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways, with formation of the Isthmus of Panama sensu stricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.
    Description: This study was supported by the Smithsonian Tropical Research Institute to A.O., J.B.C.J., N.K., and H.A.L.; the NSF (EAR 1325683) to A.O., P.G.R.-D., and E.L.G.; the National System of Investigators to A.O.; the Secretaría Nacional de Ciencia, Tecnología e Innovación (Panamá) to A.O., H.A.L., and S.E.C.; the U.S. Geological Survey to R.F.S.; and the Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina) to A.L.C., G.M.G., E.S., and L.S.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Journal of African Earth Sciences 136 (2017): 61-108, doi:10.1016/j.jafrearsci.2017.05.008.
    Description: We present a detailed geologic study of the Thebes Formation at Gebel Gurnah in its locus typicus on the West Bank (opposite Luxor) of the Nile River in the Upper Nile Valley, Egypt. This is the first detailed measurement and lithologic description of the ~ 340 m thick (predominantly) carbonate section. The Thebes Formation is divided into thirteen major lithic units (A to M). We interpret data on the lithologic succession and variations, whole rock/clay mineralogy, and macro/micropaleontology in terms of deposition on a shallow carbonate platform episodically influenced by continental runoff, and describe six depositional sequences that we place in the global framework of Lower Eocene (Ypresian) sequence stratigraphy. We note however significant incompatibilities between the Thebes depositional sequences and the global sequences. We emend the definition of the Thebes Formation by defining its top as corresponding to level 326 m at the top of Nodular Limestone ‘L’ (NLL), and assigning the overlying beds to the Minia Limestone Formation. New biostratigraphic data and revision of previous studies establish the direct assignment of the Thebes Formation to planktonic foraminiferal Zones E4/P6b (upper part), E5/P7 and (indirectly) Zone E6/P8, and (probably, indirectly) Zone E7a/”P9”, and to calcareous nannofossil Zone NP12 and lower Zone NP13 of the Lower Eocene (Ypresian) and provide a temporal framework spanning ~ 2.8 Myr from 〈52.45 to ~49.6 Ma for the deposition of the Thebes Formation prior to the prominent sea level fall (~ 49.6 Ma) towards the end of the Early Eocene. Dominantly carbonate deposition, with a strongly reduced detrital influx, occurred on a very wide shelf (probably) at least ~ 100 km from the coastline. The thick sedimentary succession and the marked vertical lithologic variations are interpreted as resulting from sea level fluctuations imprinted on a long-term decrease in sea-level associated with rapid subsidence reflecting tectonic relaxation after the major Late Paleocene tectonic reorganization of the Syrian Arc.
    Description: National Geographic Society for financial support
    Keywords: Thebes Limestone ; Lower Eocene ; Gebel Gurnah ; Egypt ; Sequence stratigraphy
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...