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<h2>Landscape, biotic and climatic evolution of Miocene
Western Amazonia: an integrated paleontological and geochemical approach</h2>

<p class=MsoNormalstyle='text-align:justify'>Frank
Wesselingh(1,2), Hubert Vonhof (3) and Ron Kaandorp (3)</p>

<p class=MsoNormal style='text-align:justify'>Miocene
fossiliferous deposits of the Pebas Formation that are present over vast areas
in Western Amazonia represent long-lived lake depositional settings. Lake
Pebas, that presumably initiated around c. 25 Myr ago in the East Andean
foreland Basin zone, and consequently moved eastward, reached its maximum size
in the late Middle Miocene, when it covered an area over 1 million square
kilometres. In the lake an endemic invertebrate (mollusc and stracod) fauna
evolved, with spectacular morphological oddities. Molluscan ecology, combined
with stable isotope geochemistry of the shells show that the lake was
essentially freshwater, apart for short intervals when (strongly diluted)
marine incursions reached the area from the north. Reconstructed climates from
shells in the lake are very similar as today's. Lake Pebas ended when the area
to the north was uplifted and the Amazon overfilled the lake tin order to
establish its modern course, ca. 8 million years ago.</p>

<p class=MsoNormal style='text-align:justify'>(1)
Naturalis, Nationaal Natuurhistorisch Museum, P.O. Box 9517, 2300 RA Leiden, NL</p>

<p class=MsoNormal>(2)
Biodiversity Centre, University of Turku, Turku, FInland</p>

<p class=MsoNormal style='text-align:justify'>(3)
Vrije Universiteit, Amsterdam, NL</p>

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