Publications and Preprints

Publications and Preprints

At the time that Darwin’s On the Origin of Species was published, the earth was “scientifically” determined to be million years old. By , it was found to be 1. In , science firmly established that the earth was 3. Finally in , it was discovered that the earth is “really” 4. In these early studies the order of sedimentary rocks and structures were used to date geologic time periods and events in a relative way. At first, the use of “key” diagnostic fossils was used to compare different areas of the geologic column. Although there were attempts to make relative age estimates, no direct dating method was available until the twentieth century. However, before this time some very popular indirect methods were available.

Evidence for the stability of the West Antarctic Ice Sheet divide for million years

Hidy FS Abstract We tested the feasibility of using cosmogenically produced beryllium-7 7Be and beryllium 10Be isotopes to date concrete, a common tunnel construction material. A series of experimental concrete and concrete component samples were analyzed for 7Be and 10Be, which led to the following key findings: Both 7Be and 10Be are present at levels detectable by accelerator mass spectrometry AMS in concrete and many concrete components cement, sand, aggregate, precipitation.

However, neither is detectable in tap water.

Cosmogenic nuclide dating of Swiss Deckenschotter ABSTRACT erosion rate and inheritance. For 36Cl, the age is modelled with MathCad codes developed by our group [8]. The method of iso-chron-burial dating however is based on the decay of the cosmogenic nuclides and uses the difference in half-lives of 10Be and 26Al. In this method, sam-.

Using cosmogenic 10Be dating to unravel the antiquity of a rocky shore platform on the west coast of Korea. Shore platforms commonly occur at the base of coastal cliffs on rocky shores. It is generally accepted that they form by the retreat of such cliffs through wave action and weathering processes. Some platforms show contemporary features; however, the possibility that some features were inherited from the last interglacial or earlier stages always exists.

The occurrence of wide shore platforms in resistant rocks is often regarded as evidence of such inheritance because the short stillstands of the Holocene offered insufficient time for the sculpting of extensive platforms on resistant rocky coasts. This study focuses on dating the wide shore platforms, which are common on headlands along the west coast of the Korean Peninsula, based on the abundance of cosmogenic 10Be.

Samples for cosmogenic 10Be surface exposure dating were collected along two transects oriented perpendicular to the cliff line. The apparent surface exposure ages of the samples ranged from the Holocene ca. Given the apparent antiquity and range of the surface exposure ages, it seems likely that this shore platform originated in the Pleistocene, when sea levels were similar to those of today, and that the present shore platform is cutting into its interglacial predecessor.

The generation and degradation of marine terraces. Basin Research 11 1:

Cosmogenic dating of fluvial terraces, Fremont River, Utah

In the sciences, it is important to distinguish between precision and accuracy. If we use the analogue of a clock we can investigate this further. Your wrist watch may measure time with a precision of one second.

Five limestone boulders from an end moraine in the Galicica Mountains (°N, °E, m a.s.l.) were used for cosmogenic 36 Cl surface exposure dating. The 36 Cl concentrations from the five boulders are identical within their measurement uncertainties ruling out major effects of inheritance, erosion, or snow cover.

This wide exceeding 1. Toreva blocks are best developed along the eastern side of the river — they exhibit coherently-dipping, patinated tops that can be reconstructed to the gorge walls, but with toes that are truncated or buried by later deposits. Located below these landslide features is a flight of fill and fill-cut terraces spanning 6 levels at elevations of 60, 45, 29, 25, 15 and 7 m above the modern river grade, on average. Terraces at 29 m can be correlated across and along the river axis, whereas others are more locally preserved.

All terraces exhibit well-defined boulder levees and risers constructed from alluvium sourced from upstream, and rounded and sculpted basalt clasts on their treads. Minimum 3He surface exposure ages of multiple samples from each terrace indicate Qt6 was likely abandoned at This incision was likely coincident with toreva block formation and substantial gorge widening, as the toreva blocks and large-scale incohesive landslide deposits predate terrace development.

Landsliding controls the width of the gorge along this stretch, leading to a These landsliding events were likely primarily driven by undercutting of basaltic bedrock along weaker gravel horizons. Gorge narrowing is observed during this time period, with only minor widening accommodated by slumping and incoherent landsliding that post-date terrace treads. These increasingly rapid incision rates mirror the phenomena seen in other western US river systems since the Pliocene.

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Repka a, Robert S. Anderson a, , Robert C. While surface exposure dating using cosmogenic10Be and 26Al would seem to be an ideal dating method, the surfaces are composed of individual clasts, each with its owncomplex history of exposure and burial. The stochastic nature of burial depth and hence in nuclide production in these clastsduring exhumation and fluvial transport, and during post-depositional stirring, results in great variability in clast nuclideconcentrations.

We present a method for dealing with the problem of pre-depositional inheritance of cosmogenic nuclides. We generate samples by amalgamating many individual clasts in order to average over their widely different exposurehistories.

Scale Derived From Terrestrial Cosmogenic troduces significant errors in surface exposure dating (Fabel et al. ; Colgan et al. ). However, in some circumstances, TCN inheritance can be constrained and used to estimate the amount of material removed during [) a [).

Five limestone boulders from an end moraine in the Galicica Mountains The 36 Cl concentrations from the five boulders are identical within their measurement uncertainties ruling out major effects of inheritance, erosion, or snow cover. The calculated ages are very consistent ranging from The applied corrections for weathering and snow shielding cause a shift to older ages in the order of magnitude of ca.

The ages point to a moraine formation during the Younger Dryas period, consistent with the timing of the last deglaciation in the Galicica Mountains derived from previous geomorphological studies in the area. The formation of a glacier was likely favoured by several topoclimatic factors, accounting for additional snow input.

exposure dating

The overall point of this paper is that they exposure-dated a large number of Holocene moraines and discovered that Holocene glacier advances in New Zealand were neither synchronous or asychronous with Northern Hemisphere glacier advances. From the perspective of cosmogenic-nuclide exposure-dating nerds, there are some other interesting features to this article that are much too obscure for the general Science readership.

Mainly, the Schaefer paper is notable because i they measured a very large number of exposure ages, ii they were very young exposure ages, and iii they are very precisely measured. Items ii and iii mainly highlight hard work in the Lamont chem lab and impressive AMS skills at LLNL-CAMS, but i is interesting because the size of the data set makes it possible to take a look at some of the beliefs that come into relating exposure ages of moraine boulders to the age of the glacier advance that formed the moraine.

They differ, for three reasons. First, all boulders could have the same true exposure age but their measured exposure ages would still differ due to measurement uncertainty.

Optical dating of loessic hillslope sediments constrains from inheritance of pre-event cosmogenic nuclides. Modern geochronology lays great emphasis on a multi-technique cosmogenic. 3. He dating of palaeorockfall boulders overlying the in .

The 10Be TCN ages show considerable variance on individual surfaces. This suggests that the predominantly bedrock hillslopes erode very slowly and sediment is transferred very gradually in most regions within Death Valley. This disparity between dates determined by different dating methods and the large spread of TCN ages suggests that the cobbles and boulders have considerable inherited 10Be concentrations, suggesting that the clasts have been derived from older shorelines or associated landforms.

These results highlight the problems associated with using surface cobbles and boulders to date Quaternary surfaces in Death Valley and emphasizes the need to combine multiple, different dating methods to accurately date landforms in similar dryland regions elsewhere in the world. However, these results highlight the potential to use TCN methods, when used in combination with other dating techniques, to examine and quantify processes such as sediment transfer and denudation in drylands.

The article included here is a pre-print. The final version of the article may be accessed via ScienceDirect.

Palaeo ice sheet reconstruction

Geomorphic process modeling allows us to evaluate different methods for estimating moraine ages from cosmogenic exposure dates, and may provide a means to identify the processes responsible for the excess scatter among exposure dates on individual moraines. Cosmogenic exposure dating is an elegant method for estimating the ages of moraines, but individual exposure dates are sometimes biased by geomorphic processes. Because exposure dates may be either “too young” or “too old,” there are a variety of methods for estimating the ages of moraines from exposure dates.

In this paper, we present Monte Carlo-based models of moraine degradation and inheritance of cosmogenic nuclides, and we use the models to examine the effectiveness of these methods. The models estimate the statistical distributions of exposure dates that we would expect to obtain from single moraines, given reasonable geomorphic assumptions.

The model of moraine degradation is based on prior examples, but the inheritance model is novel.

of surface samples collected for cosmogenic dating and dashed circle indicate the sampling area for amalgams. Red square locates position of the subsurface samples collected along the depth-profile in Fig. 5 and the OSL samples taken below the ground surface.

Most commonly employed among these are cosmogenic exposure dating, uranium-series dating, optically stimulated luminescence, and radiocarbon dating. Because the geologic samples collected may have experienced very different pre-, syn-, and post-formation histories, the dates may be interpreted as max ages, min ages, or something in between, with implications for whether a fault slip rate should be considered an upper or lower limit. For this reason, the practice of using multiple geochronometers to constrain a range of possible surface ages and slip rates is ideal and has become common enough to begin assessing how well dates obtained using different methods agree.

Where two dating methods were used, it was most common to compare exposure dates to those obtained using another method. Inheritance in exposure ages from clasts remains challenging estimate, and only in rare cases does subtracting the nuclide concentration found in the modern wash from that measured on surface bring the latter into concordance with independent dates.

Cosmogenic depth profiles are useful for estimating inheritance in the clast size sampled, but 2 in 3 depth profiles exhibited distributions too scattered for a date to be calculated. Given uncertainties related to depositional process and internal scatter in individual datasets, a review of published Quaternary geochronologic data shows the importance of dating geomorphic surfaces with more than one method in order to derive a more realistic range of surface ages.

Published Quaternary geochronologic data show the importance of dating geomorphic surfaces with multiple geochronometers.

The Secret Sun: Where There’s Smoke

I’ll never forget the day when my grandpappy and I were fishing down at the crick. The sun was going down and we were gathering up our gear and fixing to head back to the old homestead. Gramps suddenly got a weird glint in his eye and said, “Boy, when it comes to elite mind control cults and sex traffickin’, don’t you pay no never-mind to what them fancy society boys on the wireless try and tell you. Where’s there’s smoke, there’s always hellfire.

In situ cosmogenic radiocarbon production and 2-D ice flow line modeling for an Antarctic blue ice area Christo Buizert,1 Vasilii V. Petrenko,2,3 Jeffrey L. Kavanaugh,4 Kurt M. Cuffey,5 Nathaniel A. Lifton,6 Edward J. Brook,7 and Jeffrey P. Severinghaus8 Received 13 May ; revised 10 April ; accepted 12 April ; published 24 May

Burgette , Nathaniel Lifton , Katherine M. Previous studies have suggested that deformation rates on this fault vary spatially as part of the broader plate boundary system, or that the locus of deformation has migrated southward into the Los Angeles basin over the Quaternary. A well-preserved flight of fan terraces in the Arroyo Seco area of Altadena and Pasadena, CA provides a location to assess whether there is a long-term reduction in strain on the SMF.

A complementary slip-rate study Hanson et al. This project targets the prominent Gould Mesa geomorphic surface thought to be middle Pleistocene in age, locally preserved across the Central SMF. We are applying cosmogenic nuclide isochron burial dating to determine the age of the upper part of the Gould Mesa alluvial deposit.

Burial dating analyzes pairs of radionuclides 10Be and 26Al in this case produced by high-energy cosmic rays in clasts at the surface and potentially during transport that have subsequently been deeply buried. Decay of the radionuclides at different rates makes their ratio sensitive to duration of burial, and analysis with an isochron technique yields ages since burial. We collected quartz-rich cobbles from natural and roadcut exposures from m below the upper surface of Gould Mesa at two locations.

Physical sample processing is complete, and the samples are now undergoing chemical processing and analysis. Testing for slip rate changes on the Sierra Madre fault:

Rock sampling in Tongariro National Park, New Zealand

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