This dataset includes tables with physical information and isotopic data that are used to calculate uranium-series ages (230Th/U method) and initial 234U/238U activity ratios on a suite of mastodon bones from the Cerutti Mastodon site near San Diego, CA area.

This dataset includes tables of U- and Th-isotopic data used to calculate uranium-series age estimates (230Th/U method) and initial 234U/238U activity ratios for samples of pedogenic carbonate formed in soils on alluvial fans in the San Luis Valley, Colorado, USA.

This dataset includes tables of U- and Th-isotopic data used to calculate uranium-series age estimates (230Th/U method) and initial 234U/238U activity ratios for samples of pedogenic carbonate formed in soils on alluvial fans in the San Luis Valley, Colorado, USA.

The data are the results of mass spectrometer experiments to measure 40Ar/39Ar ages of sanidine crystals hosted in Yellowstone rhyolites. The data were collected using a MAP216 noble gas mass spectrometer and a Nu Noblesse noble gas mass spectrometer at the USGS facility in Menlo Park, Calif.

This dataset contains U-Pb isotopic data and associated ages of zircons from selected igneous rocks collected from the region surrounding and including the uplands of the United States Territory of Puerto Rico. The samples were collected as part of geological mapping and research conducted during 2018 and funded by the Mineral Resources Program of the U.S. Geological Survey. Zircon grains were separated and analyzed by GeoSep Services (GSS) in 2019 using laser-ablation-inductively-coupled-plasma-mass spectrometry (LA-ICP-MS) techniques.

Studies of marine terraces and their fossils can yield important information about sea level history, tectonic uplift rates, and paleozoogeography. The marine terrace record on Santa Rosa Island, California is complex. Two prominent low-elevation terraces appear to record the ~80 ka (MIS 5a) and ~120 ka (MIS 5e) high-sea stands, based on U-series dating of fossil corals, but interpretations are tentative because of clear indications of open-system behavior with respect to U-series nuclides. Nevertheless, low uplift rates are implied by a preferred interpretation of the ages. It is inferred that low late Pleistocene uplift rates, combined with glacial isostatic adjustment (GIA) processes likely resulted in reoccupation of the ~120 ka 2nd terrace during the ~100 ka (MIS 5c) high-sea stand. Study of a high-elevation marine terrace on the western part of Santa Rosa Island also shows evidence of fossil mixing. Strontium isotope ages of fossil mollusks indicate an age range of ~500 ka at one locality and ~600 ka at another locality. Consideration of elevations and ages here also yield low, long-term uplift rates, which explains, at least in part, the potential for terrace reoccupation in the early Pleistocene. In addition, however, early Pleistocene glacial-interglacial cycles were of much shorter duration, linked to the ~41 ka obliquity cycle of orbital forcing, a factor that would also enhance terrace reoccupation in regions of low uplift rate.

Studies of marine terraces and their fossils can yield important information about sea level history, tectonic uplift rates, and paleozoogeography. The marine terrace record on Santa Rosa Island, California is complex. Two prominent low-elevation terraces appear to record the ~80 ka (MIS 5a) and ~120 ka (MIS 5e) high-sea stands, based on U-series dating of fossil corals, but interpretations are tentative because of clear indications of open-system behavior with respect to U-series nuclides. Nevertheless, low uplift rates are implied by a preferred interpretation of the ages. It is inferred that low late Pleistocene uplift rates, combined with glacial isostatic adjustment (GIA) processes likely resulted in reoccupation of the ~120 ka 2nd terrace during the ~100 ka (MIS 5c) high-sea stand. Study of a high-elevation marine terrace on the western part of Santa Rosa Island also shows evidence of fossil mixing. Strontium isotope ages of fossil mollusks indicate an age range of ~500 ka at one locality and ~600 ka at another locality. Consideration of elevations and ages here also yield low, long-term uplift rates, which explains, at least in part, the potential for terrace reoccupation in the early Pleistocene. In addition, however, early Pleistocene glacial-interglacial cycles were of much shorter duration, linked to the ~41 ka obliquity cycle of orbital forcing, a factor that would also enhance terrace reoccupation in regions of low uplift rate.

This dataset contains U-Pb isotopic data and associated ages of zircons within the lithologic framework of igneous, metaigneous, and metasedimentary rocks collected from the Seldovia quadrangle in southcentral Alaska. The samples were collected as part of geological mapping and research conducted from 2020 to 2023 and funded by the Mineral Resources Program of the U.S. Geological Survey. Zircon grains were separated and analyzed by GeoSep Services (GSS). All analyses were conducted between 2021 and 2023 using laser-ablation-inductively-coupled-plasma-mass spectrometry (LA-ICP-MS) techniques. Also described in this report are the major and trace element geochemical analyses for samples collected as part of the mapping project. Analyses were conducted by ALS Global. Major elements were determined from fused bead, acid digestion, and ICP-AES analysis. Loss on ignition (LOI) was determined by furnace or TGA. Also included are rubidium (Rb), strontium (Sr), samarium (Sm), and neodymium (Nd) analyses conducted by the ALS Scandinavia laboratory in Lulea, Sweden. Samples were prepared by alkali fusion. Sr was separated using Sr-specific column (TrisKem). Nd was separated from matrix first as sum of REE using a AG50-x8 column (AlfaAesar) and then from Sm on a Ln column (TrisKem).

This data release contains 3 datasets, U-Pb isotopic data and associated ages of detrital zircon grains for 27 sedimentary rocks, whole rock major and trace-element geochemistry for 15 igneous or phosphatic rock samples, and whole rock Sr, Nd, and Pb isotopic data for 6 igneous rock samples. The samples were collected from multiple localities across Alaska as part of geological mapping and research conducted between 1974 and 2014 and funded by the Mineral Resources Program of the U.S. Geological Survey.