scholarly journals Combined Magnetostratigraphy From Three Localities of the Rainstorm Member of the Johnnie Formation in California and Nevada, United States Calibrated by Cyclostratigraphy: A 13 R/Ma Reversal Frequency for the Ediacaran

2021 ◽  
Vol 9 ◽  
Author(s):  
Kenneth P. Kodama
Keyword(s):  
United States ◽  
High Resolution ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Critical Time ◽  
Sediment Accumulation Rate ◽  
Accumulation Rates ◽  
Field Reversal ◽  
South Central ◽  
Reversal Frequency

A combined magnetostratigraphy for the Rainstorm Member of the Ediacaran Johnnie Formation was constructed using the sediment accumulation rates determined by rock magnetic cyclostratigraphy for three localities of the Rainstorm Member to provide a high resolution, time-calibrated record of geomagnetic field reversal frequency at a critical time period in Earth history. Two previously reported magnetostratigraphy records from Death Valley, California, the Nopah Range and Winters Pass Hills (Minguez et al., 2015), were combined with new paleomagnetic and cyclostratigraphic results from the Desert Range locality of the Rainstorm Member in south central Nevada, United States . The Johnnie oolite marker bed is at the base of each of the three sections and allows their regional correlation. The Nopah Range and Desert Range localities have similar sediment accumulation rates of ∼5 cm/ka, so their stratigraphic sections can be combined directly. The Winters Pass Hills locality has a higher sediment accumulation rate of 8.4 cm/ka, therefore its stratigraphic positions are multiplied by 0.6 to combine with the Desert Range and Nopah Range magnetostratigraphy. The thermal demagnetization results from the Desert Range locality isolates characteristic remanent magnetizations that indicate two nearly antipodal east-west and shallow directions and a mean paleopole (11.7˚N, 348.4˚E) that is consistent with “shallow” Ediacaran directions. The Desert Range also yields a magnetic susceptibility rock magnetic cyclostratigraphy that records short eccentricity, obliquity, and precession astronomically-forced climate cycles in the Ediacaran. The high-resolution combined magnetostratigraphy with nearly meter-scale stratigraphic spacing (nominally 23 ka, based on the Desert Range sediment accumulation rate), indicates 11 polarity intervals in a cyclostratigraphy-calibrated duration of 849 ka, indicating a reversal frequency of 13 R/Ma. The Rainstorm Member records the Shuram carbon isotope excursion, hence its age is ∼574 Ma. Given the recent cyclostratigraphy-calibrated reversal frequency of 20 R/Ma from the Zigan Formation (Levashova et al., 2021) at 547 Ma, our results show that reversal frequency was high but fluctuated during the Ediacaran.

scholarly journals Changes in Sediment Accumulation Rate in An Oxbow Lake Following Late 19Th Century Clearing of Land for Agricultural Use: A 210Pb, 137Cs, and 14C Study in Mississippi, USA

Radiocarbon ◽  
2004 ◽  
Vol 46 (2) ◽  
pp. 755-764 ◽  
Author(s):  
Gregg R Davidson ◽  
Meredith Carnley ◽  
Todd Lange ◽  
Stanley J Galicki ◽  
Andrew Douglas
Keyword(s):  
19Th Century ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Oxbow Lake ◽  
Sediment Accumulation Rate ◽  
Accumulation Rates ◽  
The West ◽  
Late 19Th Century ◽  
Modern Sediment ◽  
Agricultural Use

Sediment cores were collected from 2 sites in the forested fringe of an oxbow lake surrounded by land that was converted from forest to agricultural use in the late 19th century. The 2 sampling areas were selected to represent areas of high (West site) and low (East site) current sediment accumulation rates, based on distance from a perennially discharging stream. Modern (post settlement and land clearing) sediment accumulation rates were calculated using 210Pb and 137Cs on bulk sediment samples from 2 cores from each site. Two additional cores were collected from each site for radiocarbon analysis of twig cellulose with the assumption that most twigs in the sediment within the forested fringe fell from overhead and are contemporaneous with the sediment. Only the West site, however, yielded sufficient identifiable twig material for analysis. Modern sediment accumulation rates based on 210Pb and 137Cs fall between 0.2–0.4 cm/yr at the East site, and 0.7–1.3 cm/yr at the West site (nearest the stream inlet), with approximate agreement between the 210Pb and 137Cs methods. Modern sediment accumulation rate based on bomb-pulse 14C activity of twigs from cores from the West site is approximately 1.0 cm/yr, in agreement with the 210Pb and 137Cs results. Historic sediment accumulation rates were estimated at the West site using twigs from deeper intervals with pre-bomb 14C activity. Sediment covering approximately 1000 yr of pre-settlement sediment accumulation exhibited evidence of minor bioturbation or in-washing of reworked material, but with a clearly lower accumulation rate of less than 0.1 cm/yr.

Sediment Accumulation Rates in an Alaskan Arctic Lake Using a Modified 210Pb Technique

1985 ◽  
Vol 42 (4) ◽  
pp. 809-814 ◽  
Author(s):  
Jeffrey C. Cornwell
Keyword(s):  
Chemical Weathering ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Sediment Accumulation Rate ◽  
Biological Processes ◽  
Accumulation Rates ◽  
Surficial Sediments ◽  
Al Content ◽  
High Concentrations ◽  
Physical And Chemical

Because of high concentrations of authigenic Mn and Fe oxides in surficial sediments from Toolik Lake, Alaska, the normalization of depth and 210Pb activity scales to the sediment Al content was used for sediment accumulation rate calculations. These results are compared with the conventional 210Pb dating technique. I found the flux of 210Pb to the lake to be very low (10 dpm∙cm−2∙yr−1), and excess 210Pb is restricted to the top 5 cm of sediment. The whole lake sediment accumulation rate is about 2.7 mg∙cm−2∙yr−1 and the sediments are little disturbed by physical or biological processes. Low rates of physical and chemical weathering are responsible for the low sediment accumulation rates.

Historic sediment accumulation rates in Karlskärsviken, a bay of Lake Mälaren, Sweden

2008 ◽  
Vol 39 (2) ◽  
pp. 123-132 ◽  
Author(s):  
Gull Olli
Keyword(s):  
Transition Period ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Sediment Accumulation Rate ◽  
Accumulation Rates ◽  
Diatom Analysis ◽  
Modern Times ◽  
Long Period ◽  
Near Shore ◽  
Rate Development

Historic sediment accumulation rate development was investigated in Karlskärsviken, a bay of Lake Mälaren, by dating of sediments in cores taken from the bay. The Lake Mälaren transition period from brackish water to freshwater was determined by diatom analysis and for modern times by fly-ash (SCP) and caesium isotope Cs-137 analyses. Results show that in the long period from medieval times to about 1950, the sediment accumulation rate increased to about double in the outer section of the bay, but only by about 33% in the near shore. After that, new farmland was drained by a ditch dug in 1951 with its outlet in Karlskärsviken, which enlarged the bay catchment area by 100%, and a marina and a public beach were constructed in 1953. These catchment system changes increased considerably the inflow of particles to Karlskärsviken and the sediment accumulation in the bay, directly and mostly in the near shore, but also with some and longer term effects further out in the bay. In later times, as the ditch became overgrown by reeds and bushes, the sedimentation rate decreased again in the near shore, while it continued to increase further out in the bay. These results indicate that even relatively small and common catchment enterprises may considerably affect sediment transport to recipient bay waters.

scholarly journals High-resolution magnetostratigraphy of the upper Nacimiento Formation, San Juan Basin, New Mexico, USA: implications for basin evolution and mammalian turnover

2017 ◽  
Author(s):  
Caitlin Leslie ◽  
Daniel J. Peppe ◽  
Thomas E. Williamson ◽  
Dario Bilardello ◽  
Matthew Heizler ◽  
...  
Keyword(s):  
New Mexico ◽  
North America ◽  
Accumulation Rate ◽  
Global Climate ◽  
Sediment Accumulation ◽  
San Juan ◽  
Accumulation Rates ◽  
Fluvial System ◽  
San Juan Basin ◽  
Geomagnetic Polarity

Lower Paleocene deposits in the San Juan Basin document one of the best records of mammalian change and turnover following the Cretaceous-Paleogene extinctions and are the type section for the Puercan (Pu) and Torrejonian (To) North America Land Mammal age biozones (NALMA). One of the largest mammalian turnover events in the early Paleocene occurs between the Torrejonian 2 (To2) and Torrejonian 3 (To3) NALMA biozones. The Nacimiento Formation are the only deposits in North America where the To2-To3 mammalian turnover can be constrained, however the precise age and duration of the turnover is poorly understood due to the lack of a precise chronostratigraphic framework. We analyzed paleomagnetic samples, produced a 40Ar/39Ar detrital sanidine age, and developed a detailed lithostratigraphy for four sections of the upper Nacimiento Formation in the San Juan Basin, New Mexico (Kutz Canyon, Escavada Wash, Torreon West and East) to constrain the age and duration of the deposits and the To2-To3 turnover. The polarity stratigraphy for the four sections can be correlated to chrons C27r-C26r of the geomagnetic polarity time scale (GPTS). Using the local polarity stratigraphy for each section, we calculated a mean sediment accumulation rate and developed a precise age model, which allows us to determine the age of important late Torrejonian mammalian localities. Using the assigned ages, we estimate the To2-To3 turnover was relatively rapid and occurred over ~120 kyr (-60/+50 kyr) between 62.59 and 62.47 Ma. This rapid duration of the mammalian turnover suggests that it was driven by external forcing factors, such as environmental change driven by the progradation of the distributive fluvial system across the basin and/or changes in regional or global climate. Additionally, comparisons of the mean sediment accumulation rates between the sections that span from the basin margin to the basin center indicate that sediment accumulation rates equalized across the basin from the end of C27r through the start of C26r, suggesting an accommodation minima in the basin associated with the progradation of a distributive fluvial system into the basin. This accommodation minimum also likely led to the long hiatus of deposition between the Paleocene Nacimiento Formation and the overlying Eocene San Jose Formation.

scholarly journals A representative density profile of the North Greenland snowpack

2016 ◽  
Vol 10 (5) ◽  
pp. 1991-2002 ◽  
Author(s):  
Christoph Florian Schaller ◽  
Johannes Freitag ◽  
Sepp Kipfstuhl ◽  
Thomas Laepple ◽  
Hans Christian Steen-Larsen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Density Profile ◽  
Accumulation Rate ◽  
Sampling Technique ◽  
Data Sets ◽  
Accumulation Rates ◽  
The North ◽  
North Greenland ◽  
Good Agreement

Abstract. Along a traverse through North Greenland in May 2015 we collected snow cores up to 2 m depth and analyzed their density and water isotopic composition. A new sampling technique and an adapted algorithm for comparing data sets from different sites and aligning stratigraphic features are presented. We find good agreement of the density layering in the snowpack over hundreds of kilometers, which allows the construction of a representative density profile. The results are supported by an empirical statistical density model, which is used to generate sets of random profiles and validate the applied methods. Furthermore we are able to calculate annual accumulation rates, align melt layers and observe isotopic temperatures in the area back to 2010. Distinct relations of δ18O with both accumulation rate and density are deduced. Inter alia the depths of the 2012 melt layers and high-resolution densities are provided for applications in remote sensing.

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