An Empirical Assessment of Variable Water Content and Grain-Size on X-Ray Fluorescence Core-Scanning Measurements of Deep Sea Sediments

Maclachlan, Suzanne; Hunt, James E.; Croudace, Ian W.

doi:10.1007/978-94-017-9849-5_6

Cited by 16 publications

(14 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The fan system advanced into a poorly oxygenated basin so the event beds are unbioturbated and hence retain their original depositional character. Helium porosity measurements on Ross Formation core plugs are low ( ca 0.5%; Pierce et al ., ) as a result of early cementation and moderate compaction, implying that there are no issues with variable porosity and interstitial fluids that complicate XRF scanner interpretation of soft‐sediment cores (MacLachlan et al ., ; Flood et al ., ).…”

Section: Geological Backgroundmentioning

confidence: 99%

High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

et al. 2020

View full text Add to dashboard Cite

Hybrid event beds form when turbidity currents that transport or locally acquire significant quantities of mud decelerate. The mud dampens turbulence driving flow transformations, allowing both mud and sand to settle into dense, near‐bed fluid layers and debris flows. Quantifying details of the mud distribution vertically in what are often complex tiered deposits is critical to reconstructing flow processes and explaining the diverse bed types left by mud‐bearing gravity flows. High‐resolution X‐ray fluorescence core scanning provides continuous vertical compositional profiles that can help to constrain mud distribution at sub‐millimetre scale, offering a significant improvement over discrete sampling. The approach is applied here to cores acquired from the Pennsylvanian Ross Sandstone Formation, western Ireland, where a range of hybrid event beds have been identified. Raw X‐ray fluorescence counts are calibrated against element concentrations and mineral abundances determined on coincident core plugs, with element and element log‐ratios used as proxies to track vertical changes in abundances of quartz, illite (including mica), chlorite and calcite cement. New insights include ‘stepped’ (to higher values) as opposed to ‘saw‐tooth’ vertical changes in mud content and the presence of compositional banding that would otherwise be overlooked. Hybrid event beds in basin floor sheets that arrived ahead of the prograding fan system have significantly cleaner sandy components than those in mid‐fan lobes. The latter may imply that the heads of the currents emerging from mid‐fan channels entrained significant mud immediately before they collapsed. Many of the H3 debrites are bipartite with a sandier H3a division attributed to re‐entrainment and mixing of a trailing debris or fluid mud flow (H3b) with sand left by the forward part of the flow. Hybrid event bed structure may thus partly reflect substrate interaction and mixing during deposition, and the texture of the bed divisions may not simply mirror those in the suspensions from which they formed.

show abstract

Section: Geological Backgroundmentioning

confidence: 99%

High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Si and K, and also Ti, is absorbed by water within the sediment, reducing element intensities in the XRF spectrum (Tjallingii et al, 2007;Wilhelms-Dick et al, 2012;MacLachlan et al, 2015). The reduction in the intensity of the fluorescence from these elements as a result of absorption by interstitial water is dependent on sediment water content (Kido et al, 2006).…”

Section: The Factors Inmentioning

confidence: 99%

Signal-to-noise ratios, instrument parameters and repeatability of Itrax XRF core scan measurements of floodplain sediments

Jones

Turner

Daly

et al. 2019

Quaternary International

View full text Add to dashboard Cite

This study used signal-to-noise ratios to assess the effects of increasing Itrax XRF instrument parameters, namely tube voltage, tube current and exposure time, on XRF spectra and measurement repeatability. Tests were performed on cores from British and Irish floodplains.Seven combinations of tube voltage and current and six exposure times were compared using signal-to-noise ratios for eight target elements. Signal-to-noise ratios may be substantially improved by selecting instrument parameters, particularly tube voltage, for specific target elements. They can also be used to assess element profile suitability for interpretation by comparison with the limit of quantification. Repeatability was assessed using the standard deviation of measurements in nine repeat scans. The variation in element levels in the majority of profiles is considerably greater than the variability in individual measurements.

show abstract

“…Compositions are only taken from beneath the oxidation fronts in these deposits, as elements are preferentially mobilised above these fronts, altering the compositions (Wilson et al 1986;Jarvis & Higgs, 1987). Attempts thus far to convert XRF core scanner outputs to elemental concentrations have been moderately successful (Weltje and Tjallingii, 2008;Hunt et al, 2015aHunt et al, , 2015bMacLachlan et al, 2015).…”

Section: Itrax µXrf Compositions Of Turbidite Mudcapsmentioning

confidence: 99%

Identifying and quantifying erosion beneath the deposits of long-runout turbidity currents along their pathway

Hunt

2017

Marine Geology

View full text Add to dashboard Cite

Variations between the geochemical compositions, coccolith species compositions and the physical properties of turbidite muds and their underlying hemipelagites can be used to understand the erosive nature of sediment gravity flows. Large-volume submarine landslides on the NW Moroccan continental margin produce long-runout turbidity currents capable of traversing hundreds-to-thousands of kilometres across the adjacent Moroccan Turbidite System (MTS). These turbidity currents are responsible for turbidites that are among the largest-volume, most aerially extensive, and longest-runout deposits recorded. These resulting turbidite beds can be correlated over distances of greater than 1,800 km across the full 250,000 km 2 area of the MTS. Due to the ability to trace these individual flow deposits throughout the MTS large-volume beds A5, A7, A11, A12 and A15 can be shown to be erosive upon debouching Agadir Canyon, whilst smaller-volume flows were not erosive. These aforementioned large-volume flows have been capable of eroding up to 15 km 3 of material in the Canyon mouth, equating to as much as 50% of the later deposit volume. Evidence suggests individual flows erode up to 4.5 m of sediment within scours in the mouth of Agadir Canyon. However, these scours are greater than 8.0 m deep, indicating that several

show abstract

An Empirical Assessment of Variable Water Content and Grain-Size on X-Ray Fluorescence Core-Scanning Measurements of Deep Sea Sediments

Cited by 16 publications

References 25 publications

High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

Signal-to-noise ratios, instrument parameters and repeatability of Itrax XRF core scan measurements of floodplain sediments

Identifying and quantifying erosion beneath the deposits of long-runout turbidity currents along their pathway

Contact Info

Product

Resources

About