Dear Dr Kalyanaraman
You asked
> I have just joined the group. Would appreciate guidance on
> the relative chronology of the avestan and vedic languages.
Zaehner in his seminal work "The Dawn and Twilight of Zaroastrianism"
dates the earliest Gathas of Zarathustra at about in the period
sometime between 612 to 590 BCE. Zarathushra is seen as roughly
contemporaneous with the Median Empire. His host, King Vitaspa is
seen as having built a confederacy of Iranian tribes in the area of
Ariana into a loose kingdom. This kingdom was annexed by Cyrus the
Archaemenaeid in his campaign in Eastern Iran, and the remnants of
Visaspa's people are believed to have moved to Kwarazim (on the
shores
of the Aral Sea).
As for the Vedic language, I know that the River Saraswati is
mentioned in the early Vedas, and on geological evidence that is
supposed to have dried up about 1,500 BCE. On this ground, Sanscrit
is a lot earlier than Avestan, although of course such evidence needs
to be taken carefully.
Homer for instance, knew of a late Mycenaean seige of Troy, but the
language he wrote in was Ionian Greek, far removed from the
Paleo-Arcadian dialect the Mycenaeans are supposed to have spoken.
A similar set of events may have also occurred with Sanscrit.
Hope this helps
John