One of the successes of literary-critical scholarship on the midrashic literature has been the determination of a plausible relative chronology of the documents, based strictly on internal literary criteria (e.g., use of Hebrew vs. Palestinian Aramaic; amount of Greek and Latin employed; nature and frequency of attributions; dependence on, or literary affinity with other documents). Documents deemed to be earlier bear stylistic affinities with the Palestinian Talmud, use a fair amount of Galilean Aramaic and Greek and tend to attribute materials to a variety of Palestinian Amoraim mentioned in the Palestinian Talmud. Documents deemed to be later are mostly in Hebrew, use little Aramaic and Greek, and contain fewer attributions (many of which are suspect).
Richard S. Sarason, “Toward a New Agendum for the Study of Rabbinic Midrashic Literature,” in Studies in Aggadah, Targum and Jewish Liturgy in Memory of Joseph Heinemann, ed. Jakob J. Petuchowski & Ezra Fleischer (Jerusalem: The Magnes Press, The Hebrew University; Cincinnati: Hebrew Union College Press, 1981), 59, n. 12.