Difference between revisions of "Category:Speleothem Working Group"

Revision as of 16:18, 18 April 2017

Overview

In the Linked Earth context, a working group (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed herewith. This page is dedicated to the discussion of data and metadata standards for speleothems, and aims to formulate a set of recommendations for such a standard.

Membership

Specific tasks

We recommend that discussions focus on the following techniques, and explore potential commonalities.

For each observation type, we recommend:

• structuring discussions around what scientific questions one would want to ask of the data
• listing essential, recommended, and optional information for:
  • the measurements themselves
  • any inference made from the measurements (e.g. calibration to temperature)
  • the underlying uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
• provide an ideal data table (or link to one) for each type of observation, so the community knows what to report and how to report it.
• provide separate recommendations for new and legacy datasets

Things to describe

Site (cave)

• Site name
• Coordinates
• Elevation
• Geology
• Rock Age
• Have measurements been made of the cave environment over a season or several years (not one off)? Yes/No

Entity (speleothem)

• Entity name
• Distance from cave entrance (in m)
• Thickness of overlying bedrock above the speleothem (in m)
• Speleothem type (candlestick stalagmite, stalagmite boss, flowstone)
• Drip type (seepage, seasonal, mixture, unknown)
• Type of measurements available for that entity (stable isotopes, trace metals, organics, fluid inclusions, mineralogy, clumped isotopes, noble gas temperatures, C14, Optical Density of luminosity (ODL), Mg/Ca)
• DOI/link for raw data (e.g NOAA, PANGAEA)

References (for each speleothem)

• Citation
• DOI

Chronology

Please see the chronologies WG for generalities about U/Th dating or layer-counting. If challenges specific to dating speleothems exist, please list relevant metadata properties below.

• Date type (MC-ICP-MS, Alpha U/Th, U/Th TIMS, Annual laminations, cross-dating, c14)
• Depth of the sample (in mm)
• Thickness of the sample (in mm)
• lab number
• sample material dated (aragonite powder, calcite)
• min/max weight of sample used for dating
• Is date used in the original age model? Yes/No
• For U/Th samples: uncorrected age, 238U content, 232Th content, 230Th content, 230Th/232Th ratio, 230th/238U activity, decay constants used, corrected age, year of chemistry

Age models

• Age model type (linear between dates, polynomial fit, polynomial fit omitting outliers, bayesian, stalAge...)
• For age models based in lamina counting, evidence that laminae are annual
• For age models using C14 for deposition rate, evidence on robustness of assumed linearity

Sample data

• Distance from top of speleothem
• Thickness of analysed sample
• Evidence of equilibrium (Hendy tests)
• Year (with uncertainty)
• Measurements with precision
• Isotope standards (PDB, VPDB)
• Correction made for aragonite?

Modern Cave Conditions

The interpretation of geochemical or lithological signals embedded in speleothem archives relies sometimes heavily on implicit assumptions about cave hydrology. What parameters need to be archived to enable long-term re-use and better information extraction from speleothem datasets?

Above-Cave

• soil thickness
• vegetation type

In-Karst Hydrology

• karst residence time
• transit time distributions
• porosity
• rock overburden thickness
• flow route type

In-Cave

• Temperature
• Humidity
• pCO2
• drip-rate
• drip chemistry

References