GEOCHEMISTRY

Lucas et al. (2009) stated that they wanted to "emphasize" that the differing geochemistry of dinosaur-bone samples from the Cretaceous Kirtland Formation and the Paleocene Ojo Alamo Sandstone only demonstrates their provenance of mineralization and does not prove that the Ojo Alamo is Paleocene. This statement is in full agreement with Fassett (2009), thus it is puzzling why this emphasis was deemed necessary. These authors discuss the chemistry of the large hadrosaur femur from the Ojo Alamo Sandstone at the San Juan River locality, stating that it had "values that overlap the values of Kirtland Formation bone." It is true that the U content of this bone is quite low and thus comparable to U levels for Cretaceous bone, and that problem is addressed in Fassett (2009). It is not true, however, that the REE data for this bone are not indicative of a Paleocene age. As shown on table 2 of Fassett (2009), the San Juan River bone had a La/Yb(n) ratio of 3.2 and a Sum REE value of 1004. The mean of these values for the Ojo Alamo is 6.6 and 1624, respectively, whereas for the Kirtland Formation the mean of these values is 13.7 and 2650. It is thus clear that the REE values for the San Juan River femur fall well below the mean of Ojo Alamo Sandstone bones as is stated in Fassett (2009).