First cosmogenic exposure dates for Tiwanaku stones
Researchers presented at EGU25 the first cosmogenic-nuclide exposure dating of Tiwanaku’s stone structures, which measures how long surfaces have faced the sky.
Why it matters: Exposure dating might independently test claims of a much older Tiwanaku.
Kelly Graf, Ted Goebel and colleagues report on Shég’ Xdaltth’í’ (formerly McDonald Creek), 55 km south-southeast of Fairbanks. It has three Late Pleistocene occupation layers dated to about 13,800, 13,000 and 12,700 years ago. The oldest layer holds more than 80,000 specimens, including a distinctive hafted biface, bone and antler tools, animal remains and well-preserved activity areas.
Kathleen Springer, Jeffrey Pigati, Jessica Tierney and colleagues expanded the excavations at White Sands and found 20 stratigraphic layers with human footprints in place, alongside megafauna trackways and drag lines made by travois. New radiocarbon dates on conifer pollen, combined with dates on aquatic seeds, put the footprint sequence between 23,500 and 21,700 years ago. Pollen, biomarker and sediment data record the lake turning into a playa during a dry spell that matches Dansgaard-Oeschger event 2, about 23,200 years ago.
A Science news feature reports that Andean archaeologists are replacing the traditional Inca chronology (empire from 1438) with radiocarbon dates. At Saqsaywaman, dated charcoal suggests the site began to be remodelled with fitted masonry around 1400, with construction peaking from about 1418; the first results are in press at Antiquity.
Moore, Thackeray, West and colleagues analysed nanoparticles in peat at Wonderkrater, where an earlier study found a platinum anomaly at about 12,800 years ago. They report a 4.6-fold rise in nanoparticle numbers in a 5 cm layer, with platinum-group-rich and rare-earth-rich particle populations, which they interpret as consistent with an extraterrestrial component plus extra terrestrial dust.