February Geology and GSA Today media highlights

Sand dunes and wind-blown dust deposits are used to reconstruct drought history; these deposits are useful because they preserve information on drought for much longer than observational data. Based on 95 optical ages, Miao et al. present a 10,000-year reconstruction of dune activity and dust production in the central Great Plains, USA. The integration of data from both wind-blown sand and dust deposits is an important new aspect of this record. Clusters of ages define periods of extensive dune activity and dust production, which Miao et al. interpret as a response to severe drought, at 1.0–0.7 ka and 2.3–4.5 ka (with peaks centered on 2.5 and 3.8 ka); sustained drought occurred from 9.6 to 6.5 ka. Parts of this record may be consistent with hypotheses linking drought of the past 10,000 years to sea surface temperature anomalies in the Pacific or Atlantic oceans or to the El Niño–Southern Oscillation phenomenon, but the record as a whole is difficult to reconcile with any of these hypotheses.

Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange
Bruce J. MacFadden, Florida Museum of Natural History, Natural History Dept., Gainesville, FL 32611, USA; et al. Pages 123-126.

The extinct terror bird Titanis walleri from North America was a flightless giant estimated to have stood 2 meters tall and weigh 150 kilograms. It is known from four Neogene fossil localities in Texas and Florida. Titanis walleri was previously thought to have dispersed from South America to North America across the Isthmus of Panama during the Great American Interchange about 2.5 million years ago. Titanis was also previously thought to have become extinct during the late Pleistocene megafaunal extinction. MacFadden et al. refine the age of the dispersal and extinction of Titanis walleri using rare earth elements (REE). REE fixed in fossil Titanis walleri bones during early stages of fossilization (diagenesis) are compared to those from fossil mammal bones within the same faunas in Texas and Florida. T. walleri from Texas has a REE pattern similar to 5-million-year-old horse fossils from the Nueces River, southern Texas. Given this similarity, Titanis walleri from Texas is now interpreted to be of similar age to these 5-million-year-old horses. This bird therefore dispersed northward during the early Pliocene, some 2.5 million years earlier than the major pulse of the Great American Interchange. In Florida, Titanis walleri has REE patterns similar to 2-million-year-old late Pliocene mammals. Given this similarity, the age of this last known occurrence of Titanis walleri is now interpreted to be from the late Pliocene. The extinction of Titanis walleri did not occur during the late Pleistocene as previously thought. MacFadden et al. demonstrate the utility of using distinctive REE patterns, taken up during early diagenesis, as a means of assessing relative ages of fossils; it potentially has widespread application at other fossil localities.