mlconverter

Convert chrons to ages using selected magnetic timescale

Synopsis

gmt mlconverter [ ML_data ] [ -A ] [ -G[s] ] [ -IFZid ] [ -Tc|g|o|s ] [ GMT_V_OPT ]

Note: No space is allowed between the option flag and the associated arguments.

Description

mlconverter is a module developed as part of the Global Seafloor Fabric and Magnetic Lineation Project [see GSFML for a full description of the project]. It reads a magnetic pick data file (or stdin) and converts chron text-strings to ages using a selected magnetic time scale. The input data must be OGR/GMT data files of the form distributed by the GSFML project.

Optional Arguments

ML_data: A magnetic ML pick data OGR/GMT file. If not given then we read standard input.

-A: Append the metadata to the output records as additional columns [Default only writes lon, lat, age records].

-G[s]: Generate an extended OGR/GMT table by appending the crustal age. Append s to repair any lax chron nomenclature, if needed.

-Tc|g|o|s: Select the magnetic time scale to use. Choose from c (Cande and Kent, 1995), g (Gee and Kent, 2007), o (Ogg, 2012), or s (Gradstein, 2004) [g].

-V[level]: Select verbosity level [w]. (See full description) (See cookbook information).

-Zacut/vcut/fcut/wcut: We will attempt to assign a single quality index Q that summarize how good we believe a model fit to be. This assignment relies of four threshold values that need to be determined empirically. Here, a_cut is the minimum peak-to-trough amplitude (in Eotvos) of a model for the crossing profile [25], v_cut is the minimum variance reduction offered by the model (in %) [50], f_cu is the minimum F statistic computed for the model [50], and w_cut is a typical FZ trough width (in km) [15]. Currently, the first three quantities are used to arrive at a 5-level quality index (0-1) for fitted models, as follows: (1) Very Good: Requires model parameters to exceed all three thresholds; (0.75) Good: Requires amplitude and variance reduction to exceed thresholds; (0.5) Fair: Requires the variance reduction only to exceed its threshold; (0.25) Poor: Requires the amplitude only to exceed its threshold; and (0) Bad: None of the criteria were met. We compute separate quality indices for the trough and blend models. For the empirical trough model we only have estimates or peak-to-trough amplitude, A, and trough width, W. Here, we form the ratio (A/a_cut) over (W/w_cut), take \(\tan^{-1}\) of this ratio and scale the result to yield the range 0-1 rounded to the nearest multiple of 0.25.

-borecord[+b|l] (more …): Select native binary format for table output.

-donodata[+ccol] (more …): Replace output columns that equal NaN with nodata.

-icols[+l][+ddivisor][+sscale|d|k][+ooffset][,…][,t[word]] (more …): Select input columns and transformations (0 is first column, t is trailing text, append word to read one word only).

-ocols[+l][+ddivisor][+sscale|d|k][+ooffset][,…][,t[word]] (more …): Select output columns and transformations (0 is first column, t is trailing text, append word to write one word only).

-q[i|o][~]rows|limits[+ccol][+a|t|s] (more …): Select input or output rows or data limit(s) [all].

-^ or just -: Print a short message about the syntax of the command, then exit (Note: on Windows just use -).
-+ or just +: Print an extensive usage (help) message, including the explanation of any module-specific option (but not the GMT common options), then exit.
-? or no arguments: Print a complete usage (help) message, including the explanation of all options, then exit.
--PAR=value: Temporarily override a GMT default setting; repeatable. See gmt.conf for parameters.

Examples

To convert chrons to ages using the Cande and Kent, 1995 timescale, and append the metadata at the end of the record, try:

gmt mlconverter -A -Tc ML_datafile.gmt > convertedfile.txt

References

Wessel, P., Matthews, K. J., Müller, R. D., Mazzoni, A., Whittaker, J. M., Myhill, R., Chandler, M. T., 2015, “Semiautomatic fracture zone tracking”, Geochem. Geophys. Geosyst., 16 (7), 2462–2472. https://doi.org/10.1002/2015GC005853.