Abstract:

This dataset includes high-resolution physical, sedimentological, and geochemical data used to characterize 15 sediment cores taken from the marsh and subtidal environments in the western Terrebonne Bay, Grand Isle, and Port Sulfur areas of Louisiana. The sediment cores were retrieved from 2015 to 2017 either by hand (qty. 12) or by vibracoring (qty. 3) and range from approximately 45 cm to 265 cm length. The cores were split lengthwise and analyzed down their lengths with a suite of non-destructive and destructive analyses to characterize the physical, sedimentological, and geochemical variation.

Suggested Citation:

Besonen, Mark R.. 2019. Physical, sedimentological and geochemical data for characterization of sediment cores from Terrebonne Bay, Grand Isle, and Port Sulfur, Louisiana from 2015-12-15 to 2017-05-18. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-p8cq-8y30

Purpose:

The results provide direct information about the nature and evolution of the ecological/depositional processes and environments at the sites of interest, which in turn provides a framework for understanding and interpreting the results of other Coastal Waters Consortium (CWC) II research.

Data Parameters and Units:

File: Sediment core photomosaics Windows folder containing 18 jpg files that contain color photomosaics of all sediment cores. All sediment core photomosaics are oriented with the top/up direction to the left side of the image; i.e. the stratigraphy is progressively more recent moving from the right side of the photo mosaic to the left side. Individual frames were hand-mosaicked together with a bitmap editing program. The silver-white "tick" marks along the upper edge of each sediment core are glass beads that were embedded on the core surface to track original depths in case of dewatering and shrinkage. The three VCPSxxx series sediment cores were each split into upper and lower segments for manageability given their extended lengths, and the depths of each segment are indicated in the file names. Images of these VCPSxxx cores were captured as seamless linescan camera mosaics on a Geotek Multi-Sensor Core Logger (MSCL) track. Note that depths were reset to 0 cm on running the lower segments of these VCPSxxx series cores using the Geotek MSCL track. Thus, for these lower segments, the true depths are cumulative from the top of the segments. For example, the lower segment of core VCPS3a1 runs from 128-265 cm depth, and thus, the 43 cm depth mark in that segment actually represents a true depth in the whole core of 171 cm, i.e. 128 cm + 43 cm. File Bulk_Density_LOI_Data_sub1.xlsx, worksheets (LC1-2, LC3-1, LC5-2, T2, T4, T6, GI01, GI02, GI05, PS3a1, PS5a, PS6a, VCPS3a1, VCPS5a, VCPS6a) all contain the same data variables. Undersized extracted subsamples (and thus, not representative for calculating true bulk density values) are indicated by "n/a”. Depth (cm); Wet Bulk Density (g/cm3); Dry Bulk Density (g/cm3); Wt. % Organic; Wt. % Mixed Carbonate; Wt. % Incombustible. Worksheets VCPS3a1 GRAPE density, VCPS5a GRAPE density, VCPS6a GRAPE density: Contain inferred relative bulk density values and were obtained at 0.5 cm resolution down core as Gamma Ray Attenuation Porosity Evaluation (GRAPE) results via a Geotek Multi-Sensor Core Logger track. These are reported as raw gamma counts per second (cps) from a Cs-137 source passed through the sediment cores. File ITRAX_XRF_Compositional_Data_sub2.xlx, worksheets (VCPS3a1, VCPS5a, VCPS6a) all contain the same data variables: Depth (cm): Depth in core (cm); Cps: Counts per second; MSE: Mean Square Error; Columns D-AU: Counts for 44 elements or species of elements. File Magnetic_Susceptibility_Data_sub1.xlsx, worksheets (LC1-2, LC3-1, LC5-2, T2, T4, T6, GI01, GI02, GI05, PS3a1, PS5a, PS6a, VCPS3a1, VCPS5a, VCPS6a) all contain the same data variables: Depth (cm); Vol. Susc. Meas. In SI: sediment core magnetic susceptibility results (SI units). File Site_Collection_Information_sub2.xlsx: Core: User-defined identifier assigned to each core; Date: Date of core collection (MM/DD/YY); LAT (dec degrees): Latitude of the sample collection in decimal degrees; site LONG (dec degrees): Longitude of the sample collection site in decimal degrees; Site Description: Area of collection (subtidal or marsh); Collection Type: Mechanism of core collection (hand or vibracore). File Visible_Light_Reflectance_Spec_Data_sub2.xlsx, worksheets (LC1-2, LC3-1, LC5-2, T2, T4, T6, GI01, GI02, GI05, PS3a1, PS5a, PS6a, VCPS3a1, VCPS5a, VCPS6a) all contain the same data variables: Depth (cm); Red (avg. refl.): the average reflectance of the 590-700 nm bins for each measurement. Green (avg. refl.): the average reflectance of the 510-590 nm bins for each measurement. Blue (avg. refl.): the average reflectance of the 400-510 nm bins for each measurement. Total (avg. refl.): the total average reflectance of the 400-700 nm bins for each measurement. L*(D65): the CIELAB color space L* parameter (lightness) using the D65 standard daylight illuminant. a*(D65): the CIELAB color space a* parameter (green-red component) using the D65 standard daylight illuminant. b*(D65): the CIELAB color space b* parameter (blue-yellow component) using the D65 standard daylight illuminant. RABA 400-560: the relative absorption band area from 400-560 nm beneath the local maximum at 590 nm as defined by Rein and Sirocko (2002), which is a proxy for inferred total pigment content that is usually dominated by chlorophyll. RABD 510: the relative absorption band depth for the absorption trough centered on 510 nm as defined by Rein and Sirocko (2002), which is a proxy for inferred carotenoid pigment content given that carotenoids have a local absorption maximum at that wavelength. R570/R630 ratio: the ratio between reflectance at 570 nm and 630 nm as defined by Rein and Sirocko (2002), which is a proxy to estimate terrigenous mineroclastic composition given a shift in maximum reflectance towards shorter wavelengths, and a tilt of the reflectance spectrum curve towards longer wavelengths. 360nm-740nm: the reflectance of the 360 nm through 740 nm bins in 10 nm increments (39 columns total).

Methods:

Bulk Density Absolute bulk densities (g/cc) were obtained for the three subtidal cores (LC1-2, LC3-1, and LC5-2) as it was possible to extract subsamples with a 1.0 cc constant volume sampler. Absolute bulk densities were not obtained for any marsh cores as roots and vegetation prevented the use of a constant volume sampler. Subsamples extracted with the 1.0 cc constant volume sampler (i.e. the three subtidal core mentioned above) were centered on specific depth values; thus, depth results for those subsamples are provided as whole integer values. Subsamples extracted from the remaining 12 marsh cores were manually extracted as intervals between integer depth values; thus, depths for these subsamples are tied to 0.5 cm values. Weight percent organic matter and mixed carbonate were calculated as per Dean (1974). Weight percent incombustible content was calculated as 100% - (organic matter % + mixed carbonate %). Mixed carbonate values were not obtained for the VCSPxxx series vibracores as they were extracted with aluminum tubing, and the humic acid in the marsh peat corroded the aluminum creating an oxyhydroxide gel that dehydrates between the 550°C and 1000°C loss-on-ignition incineration temperatures. As a result of this issue, neither are incombustible content values for these marsh vibracores available as the calculation depends on mixed carbonate values as per above. Inferred relative bulk density values for the VCSPxxx series marsh vibracores were obtained at 0.5 cm resolution down core as Gamma Ray Attenuation Porosity Evaluation (GRAPE) results via a Geotek Multi-Sensor Core Logger track. These are reported as raw gamma counts per second (cps) from a Cs-137 source passed through the sediment cores; thus, lower counts indicate higher attenuation due to increased sample density, while higher counts indicate lower attenuation due to decreased sample density. These cps values have not been calibrated to actual bulk density values in g/cc as per the three subtidal cores mentioned above, however, they do reflect relative changes in bulk density down the length of the cores. These GRAPE results are provided on separate, dedicated worksheets within the workbook given their nature, and because they were measured at a different resolution than the normal bulk density and loss-on-ignition subsamples. Magnetic susceptibility readings were taken at 0.5 cm intervals down the length of each split sediment core. The MS2E sensor was oriented with the long axis of its sensing field parallel to strata (i.e. perpendicular to the core length) for maximum resolution. For the VCPSxxx series cores, the relatively high values seen at the very top and very bottom of each core segment are due to edge effects, and not actual changes in the magnetic susceptibility of the sediment cores. Visible Light Reflectance Parameters and indices were derived from visible light reflectance spectrophotometry of sediment cores using a Konica-Minolta CM-2600d Spectrophotometer and accompanying SpectraMagix NX software package. The CM-2600d Spectrophotometer captures spectral reflectance from 360-740 nm in 10 nm bins. Reflectance spectrophotometry was the first analysis performed on sediment cores immediately following the splitting to gather information before oxidation and other diagenetic processes occurred. Readings (specular component excluded) were taken at 0.5 cm intervals down the length of each sediment core using a 0.3 cm aperture. The instrument was firmly placed against the sediment core surface (covered with plastic wrap) to prevent leakage and anomalous reflections. Calibration against a CM-A145 White Calibration Plate was performed at the start of every down core analysis. Photomosaics for all cores (except for the VCPSxxx series images) were captured with a Canon EOS Digital Rebel XS DSLR camera and custom lightbox equipped with full spectrum, 5000°K, 98CRI fluorescent lighting. Camera exposure settings were manually specified, including a custom white balance using a common white plate target for all sediment cores. Individual frames were hand-mosaicked together with a bitmap editing program. Images of the VCPSxxx cores were captured as seamless linescan camera mosaics on a Geotek Multi-Sensor Core Logger (MSCL) track. Note that depths were reset to 0 cm on running the lower segments of these VCPSxxx series cores using the Geotek MSCL track. ITRAX XRF Elemental compositional data were collected only for the VCPSxxx vibracores and were obtained from the Cox Analytical Systems ITRAX XRF Corescanner in the Department of Geosciences at the University of Massachusetts Amherst. Sediment cores were scanned at 0.5 cm resolution down the length of the core using a molybdenum tube with settings at 30 kV, 55 mA, and a 30 second exposure time. Results are reported in simple counts per second (cps) to show the relative variation of elements given the difficulty of generating absolute calibrated concentrations.

Instruments:

Magnetic Susceptibility measurements were obtained with a Bartington MS3 Magnetic Susceptibility Meter and MS2E High-Resolution Surface Scanning Sensor. Visible light reflectance spectrophotometry of sediment cores data was generated using a Konica-Minolta CM-2600d Spectrophotometer and accompanying SpectraMagix NX software package. Photomosaics for all cores (except for the VCPSxxx series images) were captured with a Canon EOS Digital Rebel XS DSLR camera and custom lightbox equipped with full spectrum, 5000°K, 98CRI fluorescent lighting. Images of the VCPSxxx cores were captured as seamless linescan camera mosaics on a Geotek Multi-Sensor Core Logger (MSCL) track. Elemental compositional data for the VCPSxxx vibracores were obtained from the Cox Analytical Systems ITRAX XRF Corescanner in the Department of Geosciences at the University of Massachusetts Amherst.

Provenance and Historical References:

Walter E. Dean, Jr. (1974). Determination of Carbonate and Organic Matter in Calcareous Sediments and Sedimentary Rocks by Loss on Ignition: Comparison With Other Methods. SEPM Journal of Sedimentary Research, Vol. 44. doi:10.1306/74d729d2-2b21-11d7-8648000102c1865d Rein, B., & Sirocko, F. (2002). In-situ reflectance spectroscopy - analysing techniques for high-resolution pigment logging in sediment cores. International Journal of Earth Sciences, 91(5), 950–954. doi:10.1007/s00531-002-0264-0

Individual Files: