Topper site osl dating
These results confirm those for YDB spherules from Blackwater Draw by Firestone et al.reported that Pt, Ir, and Os values were near detection limits for spherules, and therefore, have high uncertainties.investigated sediments from Belgium, the Netherlands, Lithuania, and NW Russia near Finland, reporting sharp YDB enrichment in Pt at the YD onset, as well as other meteoritic elements such as nickel, chromium, copper, and iridium. analyzed YDB magnetic microspherules from Blackwater Draw, New Mexico using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS).They reported an abundance peak in YDB microspherules that display melted, dendritic textures, confirmed through a combination of SEM and energy dispersive spectroscopy (EDS).to have resulted from a highly fractionated, Ir-deficient, iron-rich, extraterrestrial impactor.However, ten additional YDB studies have reported different concentrations and ratios of Pt and other platinum group elements (PGE), including iridium (Ir), osmium (Os), ruthenium (Ru), and rhodium (Rh), all of which usually co-vary (Supplementary Information, “Summary of PGE Occurrence in the YDB”).Black mats have previously been claimed to be an indirect impact marker, related to environmental degradation resulting from impact-related abrupt YD climate change, but that issue is beyond the scope of this paper.
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. This Pt datum will facilitate the dating and correlating of archaeological, paleontological, and paleoenvironmental data between sequences, especially those with limited age control.
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.
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.
These other studies do not rule out an extraterrestrial impactor as source of the PGE anomalies, but do not support the conclusion that it was highly fractionated and Ir-deficient, leaving open the question of the exact nature of the Pt source (see Supplementary Information, “Potential Sources of YDB Platinum”).
Sawlowicz notes that PGE anomalies may result from multiple processes of enrichment, including: a) cometary or meteoritic influx [Supplementary Table 7]; b) impactites from an extraterrestrial impact event [Supplementary Table 7]; c) volcanoes [Supplementary Table 10]; d) mantle material, e.g., from tectonic motion or in cratons [Supplementary Table 7]; e) exhalative-hydrothermal processes; f) precipitation from seawater; g) post-depositional transport and precipitation at redox boundaries; and h) reduction from intermediate and low-temperature solutions.