Computer Science
Scientific paper
Nov 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001e%26psl.193...39p&link_type=abstract
Earth and Planetary Science Letters, Volume 193, Issue 1-2, p. 39-46.
Computer Science
3
Scientific paper
The felsic volcanics (rhyolites and rhyodacites) of the St. Mary's Islands (SMI), southern India (~13°N), were originally interpreted as a distant outlier of the ~65 Ma Deccan volcanic province of west-central India, comprising dominantly flood basalts. Later the SMI volcanics were dated at ~93 Ma by the K-Ar technique. However, this K-Ar `age' was dubious, being merely an average of five out of six widely varying dates and arbitrary data selectivity being involved in this averaging. Our first 40Ar-39Ar dating of the SMI volcanics yields excellent plateau and isochron ages, and their weighted mean isochron age is 85.6+/-0.9 Ma (2σ). Interestingly, the southern Indian Precambrian terrain is intruded by numerous mafic-doleritic dyke swarms ranging in age from Proterozoic to the latest Cretaceous (69-65 Ma, Deccan-related), and indeed, two regional dykes (a leucograbbro and a felsite) from the Kerala region of southwestern India remain previously dated at ~85 Ma, but again with the K-Ar technique. However, this age for the SMI volcanics also corresponds excellently with 40Ar-39Ar ages of ~89-85 Ma (weighted mean isochron age 87.6+/-1.2 Ma, 2σ: equivalent to 88.1+/-1.2 Ma corresponding to MMhb-1 age of 523.1+/-2.6 Ma) for the Madagascar flood basalt province. Together, therefore, the Madagascar flood basalt province, the SMI volcanics, and possibly the Kerala dykes could represent volcanic activity associated with the break-up of Greater India (India plus Seychelles) and Madagascar, thought to have occurred in the Upper Cretaceous at ~88 Ma.
Bhutani Rajneesh
Pande Kanchan
Sheth Hetu C.
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