Previously, a large platinum (Pt) anomaly was reported in the Greenland ice sheet at the Younger Dryas boundary (YDB) (12,800 Cal B.P.). In order to evaluate its geographic extent, fire-assay and inductively coupled plasma mass... more

Previously, a large platinum (Pt) anomaly was reported in the Greenland ice sheet at the Younger Dryas boundary (YDB) (12,800 Cal B.P.). In order to evaluate its geographic extent, fire-assay and inductively coupled plasma mass spectrometry (FA and ICP-MS) elemental analyses were performed on 11 widely separated archaeological bulk sedimentary sequences. We document discovery of a distinct Pt anomaly spread widely across North America and dating to the Younger Dryas (YD) onset. The apparent synchroneity of this widespread YDB Pt anomaly is consistent with Greenland Ice Sheet Project 2 (GISP2) data that indicated atmospheric input of platinum-rich dust. We expect the Pt anomaly to serve as a widely-distributed time marker horizon (datum) for identification and correlation of the onset of the YD climatic episode at 12,800 Cal B.P. This Pt datum will facilitate the dating and correlating of archaeological, paleontological, and paleoenvironmental data between sequences, especially those with limited age control. In 2013, Petaev et al. 1 discovered an anomalously large platinum (Pt) peak in ice core samples from the Greenland Ice Sheet Project 2 (GISP2), thus providing the most compelling evidence to date for a catastrophic extraterres-trial event coincident with the onset of the Younger Dryas (YD) climate episode. In the study by Petaev et al., high-resolution (2.5–4.6 y) time-series of ice core samples were analyzed for trace and major element concentrations using inductively coupled plasma mass spectrometry (ICP-MS). Petaev et al. 1 reported the presence of a Pt peak anomaly at the Bølling-Allerød/Younger Dryas Boundary (YDB), coincident with a large shift in δ 18 O values, confirming the onset of cooler conditions at the beginning of the YD interval. This peak interval is represented by a rise in Pt concentrations over 14 years and subsequent drop during the following 7 years, consistent with the known residence time of stratospheric dust 1. This sharply defined Pt anomaly at the YD onset in GISP2 is coeval with other YDB impact-related proxies, including nanodiamonds and melted spherules, found in Greenland and across four continents and is proposed by Petaev et al. to have resulted from a highly fractionated, Ir-deficient, iron-rich, extraterrestrial impactor. However, ten additional YDB studies have reported different concentrations