(Photo © Gigi Cohen)

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Dr. Stephen R. Meyers (he/him)
Vilas Distinguished Professor

Department of Geoscience
UW-Madison

Ph.D., Northwestern University, 2003

Research Interests:
Paleoclimatology & Paleoceanography, Quantitative Stratigraphy, Sedimentary Geochemistry, Statistics & Data Analysis

VIEW Google Scholar Citations

Astrochron is an "open-source" computational platform for conducting, and learning about: (1) paleoclimate time series analysis, (2) astronomical time scale construction, and (3) the statistical integration of astrochronologies with other geochronologic/chronostratigraphic data (e.g., radioisotopic geochronology). An ultimate goal of the project is to facilitate efficient and transparent communication of the analytical approaches used, enabling rapid verification of results, while fostering science & methodological innovation through community involvement. Astrochron is written for R, the free software for statistical computing and graphics.

Since its launch in 2014, Astrochron has grown to include a wide range of statistical tools for paleoclimate time series analysis, chronostratigraphy and geochronology, including numerous statistical approaches developed by our research group. Astrochron also provides an integrated learning environment for instruction on the software — and the mathematical/statistical concepts that underlie the analyses — through manuals, tutorials and modeling tools.

The software incorporates functions that fall into eight basic categories: (1) data preparation, (2) spectral analysis, (3) astrochronologic testing and time scale construction, (4) filtering, (5) data visualization and general R tools, (6) radioisotope geochronology, (7) modeling and educational tools, (8) other statistical methods.

See these instructions for the installation of R and Astrochron: PDF

See this graphic for a summary of the functions available in Astrochron: PDF

You can find the official CRAN Astrochron manual here: PDF

Version 1.1 of Astrochron (2021-11-05) includes the following improvements:

timeOptSimPwrLaw - new function to perform Monte Carlo power law (1/f) simulations to evaluate significance of TimeOpt results

mwinGrid - new function determines 'dynamic moving window' for stratigraphic series, output on evenly spaced grid

mwStatsGrid - new function for 'dynamic window' moving average, median and variance on evenly spaced grid

conv_fft - new function for convolution through Fast Fourier Transform

bioturb - new function to bioturbate time series using diffusion model from Guinasso and Schinck (1975)

unbioturb - new bioturbation removal function following the approach of Liu et al (2021)

deconv - new function for Wiener deconvolution through Fast Fourier Transform

impulseResponse - new function for impulse response function calculation

peak - added option to output the plateau points that are not evaluated

trough - added option to output the plateau points that are not evaluated

autoPlot - added dmin and dmax options

timeOptTemplate - added option to output sedimentation rate at each depth or height

slideCor - linear detrending option added, new minpts default, minpts reset to maximum possible when specified value is too large, plotting modifications

added viridis as default color scale for these functions: eha, plotEha, eTimeOpt, eAsm, integratePower, traceFreq, trackFreq, tracePeak, trackPeak, mwinStatsGrid

assorted modifications for CRAN compliance

Version 1.0 of Astrochron (2021-02-10) includes the following improvements:

mwMinMax - new function for assessment of maxima and minima in stratigraphic series

pl - added a range of output file formats (e.g., jpeg, png, ...)

readMatrix - added verbose option

mwStats - now gives warning when there is one data point in a window, instead of exiting

mwStats - added CI option for confidence intervals on mean value

mwStats - now evaluates ends of series when conv=1

repl0 - now handles NaN
replEps - now handles NaN

surrogateCor - now outputs correlation coefficient and p-value to console

timeOpt - when numsed is set to 1, will now evaluate sedmin

eTimeOpt - updated for numsed=1 option

Version 0.9 of Astrochron (2019-01-08) includes the following improvements:

ar1etp - updated plots (option pl), and added option to exclusively evaluate noise (wtAR<0)

detrend - added option to output linear trend

diffAccum - model differential sediment accumulation across lithofacies

getData - added data sets 607-18O, AEB-18O, Newark-rank, CDL-rank, DVCP2017-18O

getLaskar - added 65 deg. North insolation, summer solstice

imbrie - an implementation of the Imbrie and Imbrie (1980) ice sheet model

lowspec - added option to allow log frequency plotting (option pl).

mtm - added option to allow log frequency plotting (option pl).

mtmML96 - added option to allow log frequency plotting (option pl).

mtmPL - added option to allow log frequency plotting (option pl); corrected for round-off error on default flow estimation

multiTest - added output option

read - added verbose option; if averaging is performed, original data points are plotted for comparison.

sortNave - if averaging is performed, original data points are plotted for comparison.

synthStrat - synthesize stratigraphy from forcing function

testPrecession - significance testing algorithm updated

testTilt - new function for astrochronologic testing via the obliquity amplitude modulation approach of Zeeden et al. (2019 submitted).

timeOptTemplate - new function for timeOpt approach with sedimentation templates of Meyers (2019)

timeOptTemplateSim - new function for significance testing for timeOptTemplate (Meyers, 2019)

tune - added new warning message when control has only one line

Other assorted code/documentation improvements

Version 0.8 of Astrochron (2018-05-16) includes the following improvements:

calcPeriods - new function to calculate eccentricity and precession periods in ka, given g and k in arcsec/yr

confAdjust - new function to adjust spectrum confidence levels for multiple comparisons, using the Bonferroni correction

eTimeOpt - new function for evolutive implementation of timeOpt

eTimeOptTrack - new function to track eTimeOpt maxima

makeNoise - new function to generate noise surrogates from a theoretical power spectrum

mtmPL - new function for multitaper method (MTM) spectral analysis with power law (1/f) fit

multiTest - new function to adjust spectral p-values for multiple comparisons, using a range of approaches

pwrLaw - new function to generate power law (1/f) noise surrogates, following the algorithm of Timmer and Konig (1995)

pwrLawFit - new function to estimate power law (1/f) fit to power spectrum, following the algorithm of Vaughan (2005)

testBackground - new simulation tool to evaluate power spectrum false positive rates, etc.

timeOptMCMC - new function to implement the Markov-Chain Monte Carlo timeOpt approach of Meyers & Malinverno (2018)

tracePeak - new tool to interactively trace peak trajectories on plots

trackPeak - new tool to interactively select points to track peak trajectories on plots

timeOptSim - now implements a new p-value estimation procedure

Other assorted code/documentation improvements

Version 0.7 of Astrochron (2017-06-14) includes the following improvements:

slideCor - new function to identify optimal spatial/temporal shift to maximize correlation between two stratigraphic series

mwin - new function to determine 'dynamic moving window' for stratigraphic series, adjusting for changing sample density to maintain a window of constant duration

mwCor - new function to calculate moving window correlation coefficient for two stratigraphic series, using a 'dynamic window'

mwStats - new function for 'dynamic window' moving average, median and variance of stratigraphic series

timeOptPlot - new function to generate summary figure for TimeOpt analyses

timeOpt - new features added

Other assorted code/documentation improvements

Version 0.6.6 of Astrochron (2017-03-20) includes the following improvements:

'Native routine registration' has been updated to be compliant with CRAN standards

eha & plotEha include new color palettes, which are compatible with the formatting used by the journal Nature.

timeOpt includes a new graphical output when one sedimentation rate is investigated

Other minor code improvements

Version 0.6.5 of Astrochron (2016-09-05) is a minor upgrade, with assorted modifications to improve performance.

Version 0.6 of Astrochron (2016-06-16) includes the following improvements:

surrogateCor - a new statistical approach to estimate the correlation coefficient and associated p-value for two stratigraphic data sets with different sampling grids (Baddouh et al., 2016, EPSL)

rmNA - new function to remove stratigraphic levels from your data frame if they contain one or more NAs.

mtm - now outputs 90%, 95% and 99% AR1 confidence levels, when output=1.

mtmML96 - now outputs 90%, 95% and 99% robust AR1 confidence levels, when output=1.

Assorted code improvements

Version 0.5 of Astrochron (2015-12-18) includes the following improvements:

timeOpt - new function for evaluation of eccentricity-related amplitude modulation and bundling in paleoclimate data using the method of Meyers (2015, Paleoceanography)

getData - new function to download data files from the astrochron server

Assorted code improvements

Version 0.4.3 of Astrochron (2015-07-01) is a minor upgrade.

Version 0.4.2 of Astrochron (2015-03-19) includes the following improvements:

testPrecession - new function for the Zeeden et al. (2015, Paleoceanography) amplitude modulation test

mtmML96 - a new version of the Mann and Lees (1996) robust red noise approach that solves the "edge effect" problem (see Meyers, 2012)

mtmAR - new function to test your spectrum against higher order AR models (the "intermediate spectrum" test of Thomson et al. (2001))

integratePower - new function to integrate evolutionary power spectra

taner - new function for Taner bandpass/lowpass filter

surrogates - new function to generate phase randomized surrogates as in Ebisuzaki (1997)

getLaskar - new function to automatically download Laskar et al. astronomical solutions (LA04, LA10a, LA10b, LA10c, LA10d, LA11)

stepHeat - new function to evaluate incremental heating Ar/Ar data

wtMean - new function to evaluate total fusion Ar/Ar data

Code optimization throughout, to speed things up!