Javelina Formation

The Javelina Formation is a geological formation in Texas. Dating has shown that the strata date to the Maastrichtian stage of the Late Cretaceous, approximately 70 to 66.5 million years old. The middle part of the formation has been dated to about 69 million years ago plus or minus 1 million years and the top situated near the Cretaceous–Paleogene boundary, dated to 66 Ma ago. Dinosaur remains are among the fossils that have been recovered from the formation.

Age

The typical age range of the Javelina Formation has been difficult to determine. In 2006, the middle portion of the Javenila Formation about below the K-Pg boundary was dated to million years ago by Lehman and colleagues. Using this date, in correlation with a measured age from the underlying Aguja Formation and the likely location of the K-Pg boundary in the overlying Black Peaks Formation, the authors argued that the Alamosaurus fauna seems to have lasted from about 70–66 million years ago, with the earliest records of Alamosaurus near the base of the Javelina Formation and the latest just below the K-Pg boundary in the Black Peaks Formation. However, Leslie et al. and Lehman et al. later corrected this age estimate, since the dinosaur fossils are actually known from the upper portion of the Javelina Formation. The K-Pg boundary of the Javelina Formation is known to be at the ~ level, and the youngest-known Alamosaurus fossil-bearing locality is known from the top of the sandstone unit at ~ level, approximately ~ below the K-Pg boundary. With dating based on magnetostratigraphy constraining the maximum depositional age of the dinosaur fossil-bearing section at approximately 66.4 million years ago, the Alamosaurus fauna can be dated to the latest Maastrichtian age.

Fossil content

Vertebrate paleofauna

Dinosaurs

Ankylosaurs

Ceratopsians

Hadrosaurs

Sauropods

Theropods

Flora

Woody dicots and angiosperms have been unearthed in this formation. Plant fossils indicate that this area was a woodland habitat.