ts01.pdf ArArAnalyses_FINAL.pdfPDF document, 117K | ^{40}Ar/^{39}Ar analyses of Alpha Ridge sample PS051-041-1CC |

ts02.pdf_Summary_of_Incremental_Heating_Data.pdfPDF document, 49K | Incremental heating summary table containing the most important data to calculate the ages and to build the age and K/Ca spectra plots. For each incremental heating step, it lists the ^{36}Ar (in volts, from the atmospheric component), ^{37}Ar (in volts, from calcium), ^{38}Ar (in volts, from chlorine), ^{39}Ar (in volts, from potassium), ^{40}Ar (in volts, from radiogenic argon), the calculated age (plus 2σ uncertainty), the percent radiogenic ^{40}Ar as recorded in that step, the percent ^{39}Ar (from potassium) in that step relative to the total amount of ^{39}Ar released in the experiment (a proxy for the step size), and the calculated K/Ca ratio (plus 2σ uncertainty). In the first column, the laboratory analysis number is listed, and in the second column, the power (in watts) for the CO_{2} laser used to heat up the sample material is listed. The blue checkmarks indicate the steps included in the calculations of the plateau age. The results section provides the weighted means for the age plateau in terms of the ^{40}Ar/^{39}Ar ratio, its related age, and the K/Ca ratio. The mean square of weighted deviations (MSWD) and its probability (in %) are given, as well as the total width of the age plateau (in %) and the total number of steps included in the age plateau. The results give an age plateau if the MSWD (dependent on *n*) is smaller than the shown 2σ confidence limit, but if the MSWD is larger, the results are denoted as an error plateau. Finally, the total fusion age is reported, computationally combining all steps (including the steps excluded in the age plateau calculation) into a single fraction (summations are reported below the upper table) and then calculating the ^{40}Ar/^{39}Ar ratio and its related age. The same is done for the K/Ca ratio. The uncertainties on the ages given (directly next to the ages) are internal errors, including the error on the *J* value. Analytical errors have these *J* value uncertainties subtracted, whereas external errors include uncertainties on the total decay constant. |

ts03.pdf_Normal_Isochron_Table.pdfPDF document, 47K | Normal isochron summary table listing the ^{39}Ar(*k*)/^{36}Ar(*a*) and ^{40}Ar(*a* + *r*)/^{36}Ar(*a*) ratios (plus 2σ uncertainties) used for the normal isochron age calculation, as well as the correlation coefficient (r.i.) that is used in the same calculation and denotes the amount of correlation between the errors in both ratios (with numbers approaching “1” indicating strongly correlated errors). In the first column, the laboratory analysis number is listed, and in the second column, the power (in watts) for the CO_{2} laser used to heat up the sample material is listed. The blue checkmarks indicate the steps included in the calculations of the isochron age. The results section lists the ^{40}Ar(*r*)/^{39}Ar(*k*) ratio and its related age as derived from the slope of the isochron, as well as the intercept ^{40}Ar(*a*)/^{36}Ar(*a*) value, which provides an estimate of the composition of the trapped (initial) argon in the geological material. The statistics section lists computational information about the isochron calculations. The mean square of weighted deviations (MSWD) and its probability (in %) are given. The results give an isochron if the MSWD (dependent on *n*) is smaller than the shown 2σ confidence limit, but if the MSWD is larger, the results are denoted as an error chron. The uncertainties on the ages given (directly next to the ages) are internal errors, including the error on the *J* value. Analytical errors have these *J* value uncertainties subtracted, whereas external errors include uncertainties on the total decay constant. By definition, the data points selected for the normal isochron are the same as those defining the age plateau, allowing for a direct comparison between the plateau and isochron age calculations. |

ts04.pdf_Inverse_Isochron_Table.pdfPDF document, 49K | Inverse isochron summary table listing the ^{39}Ar(*k*)/^{40}Ar(*a* + *r*) and ^{36}Ar(*a*)/^{40}Ar(*a* + *r*) ratios (plus 2σ uncertainties) used for the inverse isochron age calculation, as well as the correlation coefficient (r.i.) that is used in the same calculation and denote the amount of correlation between the errors in both ratios (with numbers approaching “0” indicating no correlated errors). In the first column, the laboratory analysis number is listed, and in the second column, the power (in watts) for the CO_{2} laser used to heat up the sample material is listed. The blue checkmarks indicate the steps included in the calculations of the isochron age. The results section lists the ^{40}Ar(*r*)/^{39}Ar(*k*) ratio and its related age as derived from the intercept of the isochron on the ^{39}Ar(*k*)/^{40}Ar(*a* + *r*) *x* axis, as well as the (inverse) intercept ^{40}Ar(*a*)/^{36}Ar(*a*) value on the *y* axis, which provides an estimate of the composition of the trapped (initial) argon in the geological material. The statistics section lists computational information about the isochron calculations, including the spreading factor (in %) of the data along the isochron. The mean square of weighted deviations (MSWD) and its probability (in %) are given. The results give an isochron if the MSWD (dependent on *n*) is smaller than the shown 2σ confidence limit, but if the MSWD is larger, the results are denoted as an error chron. The uncertainties on the ages given (directly next to the ages) are internal errors, including the error on the *J* value. Analytical errors have these *J* value uncertainties subtracted, whereas external errors include uncertainties on the total decay constant. By definition, the data points selected for the inverse isochron are the same as those defining the age plateau, allowing for a direct comparison between the plateau and isochron age calculations. |

ts05.pdf_Relative_Abundances_Table.pdfPDF document, 53K | Relative abundances table containing the relative abundances of ^{36}Ar, ^{37}Ar, ^{38}Ar, ^{39}Ar, and ^{40}Ar (plus their % 1σ uncertainties) as measured in each incremental heating step. These relative abundances (in volts) are corrected for blanks, mass fractionation, and radioactive decay (for ^{37}Ar and ^{39}Ar). The summations of each of these relative abundances are reported below the upper table and used for the total fusion age and K/Ca ratio calculations. Furthermore, this table includes the calculated age (plus 2σ uncertainty), the percent radiogenic ^{40}Ar as recorded in that step, the percent ^{39}Ar (from potassium) in that step relative to the total amount of ^{39}Ar released in the experiment (a proxy for the step size), and the calculated K/Ca ratio (plus 2σ uncertainty). In the first column, the laboratory analysis number is listed, and in the second column, the power (in watts) for the CO_{2} laser used to heat up the sample material is listed. The blue checkmarks indicate the steps included in the calculations of the plateau and isochron ages. The results section simply repeats the information from the age plateau, normal isochron, and inverse isochron, as described above. Finally, this table lists important metadata on the analysis (IGSN number, preferred age, age classification, experiment type, extraction method, heating and vacuum isolation time, instrument, lithology, and lat-lon) and the constants used in the age calculations (decay constants, production ratios, and equation sets used). |

fs01.pdf_Age_Plateau_Diagram.pdfPDF document, 26K | Age plateau plot showing the age spectra resulting from the incremental heating, with the black horizontal bar indicating the location of the age plateau. All errors shown are 2σ. |

fs02.pdf_KCa_Plateau_Diagram.pdfPDF document, 27K | K/Ca plateau plot showing the K/Ca spectra resulting from the incremental heating, with the black horizontal bar indicating the location of the age plateau. All errors shown are 2σ. |

fs03.pdf_Normal_Isochron_Diagram.pdfPDF document, 31K | Normal isochron plot showing the resulting isochron (pink line), with green squares indicating the points included in the calculation. Blue squares are the excluded data points, while the red circle denotes the location of the total fusion point, which should fall on the isochron if the rock or mineral has remained a closed system since its eruption and/or crystallization. The black line is the reference line, starting with a ^{40}Ar/^{36}Ar intercept of 295.5 and assuming the plateau age to set its slope. All errors shown are 2σ. |

fs04.pdf_Inverse_Isochron_Diagram.pdfPDF document, 31K | Inverse isochron plot showing the resulting isochron (pink line), with green squares indicating the points included in the calculation. Blue squares are the excluded data points, while the red circle denotes the location of the total fusion point, which should fall on the isochron if the rock or mineral has remained a closed system since its eruption and/or crystallization. The black line is the reference line, starting with a (inverse) ^{40}Ar/^{36}Ar intercept of 295.5 on the ^{36}Ar/^{40}Ar axis and assuming the plateau age to set the other intercept on the ^{39}Ar/^{40}Ar. |

fs05.pdfPDF document, 26K | TiO_{2}-MnO-Na_{2}O discrimination diagram for pyroxenes from *Nisbet and Pearce* [1977]. CESAR: Sample recovered from the Alpha Ridge [*Jackson et al*., 1985] during the Canadian CESAR expedition. Abbreviations are as follows: A, volcanic arc basalt (VAB) oceanic and continental; B, ocean floor basalt (OFB); C, within plate alkali basalt (WPA); D, all types; E, within-plate tholeiites (WPT) + WPA + VAB; F, VAB + WPA. |

readmeFINAL.docWord 2007 document, 69K | Supporting information |