Radiometric ages on file in the Radiometric Age Data Bank (RADB) of rocks from Massachusetts
Robert Eugene Zartman, Richard F. Marvin · Antarctica A Keystone in a Changing World · 1987
This Open-File Report contains the records of radlometrlc ages for Massachusetts from the Radlometrlc Age Data Bank of the U.S. Geological Survey.These data were compiled for use In the assignment of ages to rock units portrayed on a new bedrock geologic map of Massachusetts (Zen, 1983).The compilation Is believed to document all radlometrlc ages on samples from the state that have appeared In the published scientific literature through the year 1986.Most of the Information contained herein Is self -explanatory, although the reader Is advised to consult the User's Guide to the Radlometrlc Age Data Bank (Zartman and others, 1976) In order to fully understand the construction of the record.For brevity, certain material Is entered on the record In coded format, and to facilitate the reading of this report, crucial code listings are Included as an appendix.Also, repetition of full literature references has been avoided by giving those citations only at the end of the report keyed to the reference number contained on each record.All radlometrlc ages contained In this compilation have been recalculated to common values of the decay constants (Stelger and Jager, 1977) regardless of the usage of the original authors.Thus, a consistent, direct Inter comparison of ages Is possible among all of the data regardless of the laboratory where the analysis was made.The decay constants to which the age reported herein have been calculated are: 40 Potassium A fi =4.962 x IcT^yr" 1 ; A =0.581 x lo'^yr"" 1 P e 40K/K=:0.01167atom percent 87 Rubidium \ =1 .42x 10" 1 ^r" 1 V? A=l.55125 x lO'^yr" 1 ; 238U/ 235 U= 137.88 A=9.8485 x A=4.9475 x Uranium fission X-.n8.46 x 10 yr Lead-alpha t(ml 11 ion years)=[Pb(ppm)/Alpha activity(a/mg-hr)] x 2580Records are arranged in the same order as they will appear In a forthcoming U.S. Geological Professional Paper to accompany the bedrock geologic map.Primary classification Is by geologic terrane, and within each terrane rock units are presented according to Increasing age as they appear on the Bedrock Geologic Map of Massachusetts (Zen, 1983).