Data from: Miocene flooding events of western Amazonia

There is a considerable controversy about whether western Amazonia was
ever covered by marine waters during the Miocene [23 to 5 Ma (million
years ago)]. We investigated the possible occurrence of Miocene marine
incursions in the Llanos and Amazonas/Solimões basins, using
sedimentological and palynological data from two sediment cores taken in
eastern Colombia and northwestern Brazil together with seismic
information. We observed two distinct marine intervals in the Llanos
Basin, an early Miocene that lasted ~0.9 My (million years) (18.1 to 17.2
Ma) and a middle Miocene that lasted ~3.7 My (16.1 to 12.4 Ma). These two
marine intervals are also seen in Amazonas/Solimões Basin (northwestern
Amazonia) but were much shorter in duration, ~0.2 My (18.0 to 17.8 Ma) and
~0.4 My (14.1 to 13.7 Ma), respectively. Our results indicate that shallow
marine waters covered the region at least twice during the Miocene, but
the events were short-lived, rather than a continuous full-marine
occupancy of Amazonian landscape over millions of years.