Abstract:

Short-lived Radioisotope (SLR) data are generated for selected core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to base of cores. SLR data generated include sample activity (dpm/g) of: 1) Excess 234Th activity, which is calculated by measuring the total 234Th activity and the subtraction of the measured or estimated “background” 234Th activity, 2) Excess 210Pb activity, which is calculated by measuring the total 210Pb activity and subtraction of the measured background 210Pb activity (average of 214Pb; 295keV, 214Pb: 351keV, and 214Bi; 609keV), 3) 137Cs activity, and 4) 7Be activity. Where appropriate, age dating is calculated in calendar years for 234Th and 210Pb activity profiles, as well as linear accumulation rates (LAR) expressed as cm/yr, and mass accumulation rates (MAR) expressed as g/cm2/yr.

Suggested Citation:

Brooks, Gregg. 2015. Short-lived radioisotope geochronology. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7VT1Q1Z

Publications:

Brooks, G. R., Larson, R. A., Schwing, P. T., Romero, I., Moore, C., Reichart, G.-J., … Hollander, D. (2015). Sedimentation Pulse in the NE Gulf of Mexico following the 2010 DWH Blowout. PLoS ONE, 10(7), e0132341. doi:10.1371/journal.pone.0132341

Hastings, D. W., Schwing, P. T., Brooks, G. R., Larson, R. A., Morford, J. L., Roeder, T., … Hollander, D. J. (2014). Changes in sediment redox conditions following the BP DWH blowout event. Deep Sea Research Part II: Topical Studies in Oceanography. doi:10.1016/j.dsr2.2014.12.009

Schwing, P. T., Romero, I. C., Larson, R. A., O’Malley, B. J., Fridrik, E. E., Goddard, E. A., … Mulhollan, J. (2016). Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod. JoVE, (114). doi:10.3791/54363

Ellis, S., & Fillingham, K. (2019). The Gulf of Mexico Research Initiative Information and Data Cooperative: Data Transparency and Data Sharing + Classroom Activity. Current: The Journal of Marine Education, 33(1), 42. doi:10.5334/cjme.24

Purpose:

Determine short-lived radioisotope activities, geochronology, accumulation rates

Data Parameters and Units:

Total 234Th (63keV) activity (dpm/g) Total 210Pb (46keV) activity (dpm/g) 214Pb (295keV) activity (dpm/g) 214Pb (351keV) activity (dpm/g) 214Bi (609keV) activity (dpm/g) 137Cs (661keV) activity (dpm/g) 7Be (477keV) activity (dpm/g) CRS Age dating (yrs) and MAR (g/cm2/yr) 210Pb and 234Th

Methods:

Data were corrected for counting time, detector efficiency and varying geometry using the IAEA RGU-1 standards for calibration, as well as for the fraction of the total radioisotope measured yielding activity in dpm/g. CRS (Constant Rate of Supply) Model applied to assign a date to each individual sample and calculate LAR. LAR = linear accumulation rate (cm/yr) MAR (g/cm2/yr) = dry bulk density (g/cm3) x LAR (cm/yr) CRS (Constant Rate of Supply) Model applied to assign a date to each individual sample

Instruments:

Series HPGe (High-Purity Germanium) Coaxial Planar Photon Detectors

Error Analysis:

Peak error

Individual Files: