The work on omens attributed to ushanA kAvya the bhArgava (narrated by kAvya to nArada the kANva) is a well-known hindu work that formed the basis for many such future works that are abundant in Sanskrit literature. In thrust and content it is related to another text covering a similar topic the adbhutAnIya parishiShTha of the pAraskara gR^ihya sUtra. Not surprisingly we find formulaic repetitions of the omens mentioned in it in the rAmAyaNa, mahAbhArata, purANas and some kAvyas. It also finds mention in the bR^ihat saMhitA of varAha mihira, the mideaval Hindu natural historian. The modern western critic has found ample material in the quaint superstitions of the adbhutAnI to lampoon the Hindus and their primitive ways. However, it is little accepted that these omens were an integral part of the belief system of the Western intellectual heroes, who today are placed on strange pedestals outside their natural context. Thus, in Greece we have Pythagoras, Democritus the atomist and Socrates have all asserted the importance of these omens and held firm belief in them. In fact the Greeks had a text similar to the adbhutAnI which was composed by Aristander of Macedonia. The Romans similarly mention their own adbhutAnI text, the Ostentarium Tuscum, which was also in use amongst the Etruscans, a non-Indo-European people. Parallel to varAha mihira we also encounter a similar compilation of prodigia (as adbhutAnI were referred to by the Romans) in Pliny’s text Natural Historia. We also have other Roman compilations of the same in the works of Valerius Maximus and Julius Obsequens. Thus, one may conclude that the belief in adbhutAnI and their prognostic nature was firmly rooted throughout the pagan Indo-European world- east and west as also their non-IE neighbors. Interestingly, the basic system behind these omens was pretty similar across these ancient peoples, suggesting their common origin in the Eurasiatic world, followed by divergences, by incorporating local systems.
Idea here is to merely examine some general features pertaining to the relative era of their composition in the world of Sanskrit literature, not their contents in depth.
-traditional nakShatra based months as well as zodiacal constellations are used: e.g magha, shravaNa, and siMhA (Leo) are mentioned. The planets budha (Mercury), shukra (Venus), bR^ihaspati (Jupiter) are mentioned
-temples termed chaityas and associated holy trees (chaitya vR^ikShas) are mentioned.
-idols of gods, li~Ngas and pictures of gods (chitrANi) and seats of deities (AyatanAnI) are mentioned.
-volcanic eruptions from ponds, lakes and mountains, cyclones and earthquakes are mentioned.
-Several traditional holy fig trees of the Hindus are mentioned: plakSha (Ficus infectoria), ashvatta (Ficus religiosa), udumbara (Ficus glomerata), nyagrodha (banyan, Ficus benghalensis) all together and the knowledge of their not having regular flower morphology is implicit.
-The 3 dvija varNas are mentioned, and the old equivalence of dasyus and shudras is implicit.
-indra is the prominent deity (also called pAkashAsana) and the annual public indra festival and the erection of the indra flag is alluded to.
-The other gods mentioned include: pitAmaha/prajApati, soma, dharma, yama, agni (=pAvaka), vAta (=vAyu), kubera along with maNibhadra and the yakShas, vAsudeva (meaning viShNu), varuNa, mahAdeva (=rudra), skanda-vishAkha, vishvakarman (=tvaShTa) and gandharvas.
-The goddesses mentioned are: indrANI, varuNAnI, bhadrakAlI, mahAbalA, vIramAtA.
-As an protection against prognostications of the adbhutAnI the text recommends the performance of the mahAshAntI rite with offerings to indra, rudra and the vishvedevas.
The mention of the deities skanda-vishAkha, mahAkAlI (along with vIramAtA and mahAbalA), point to the latest vedic period where these para-vedic elements were making their entry. This is also consistent with the use of the term vAsudeva for viShNu along with pitAmaha for prajApati. The non-mention of later paurANic deities like the full-blown vinAyaka place this text before the tantro-paurANic expansion of the pantheon. The prominence of indra and his public festival is still the mainstay. In these features text matches the core epic period, where some of the same deities are mentioned the first time. The chaityas, li~Ngas and pictures and idols also point to the latest vedic period when these elements were coming into the mainstream from pAra-vedic streams of Indo-Aryan culture. Some of these elements may be of very archaic para-vedic provenance, going back to the Indus Valley period. While the fig trees are important in the vedic ritual itself (with the ashvatta as the tree of indra), their association with chaityas as chaitya vR^ikShas is possibly an IVC element. We have several IVC pictograms showing the horned deity associated with the ashvatta, a stylized shrine with an ashvatta tree, or depictions of the nyagrodha. There is also an interesting IVC seal with the female form of the horned deity being worshipped in the middle of the ashvatta tree by the male one. This is likely to be the precursor of the tantric vaTa yakShini.
In my opinion the important point here is that the para-vedic elements enter the mainstream in a major way only in the latest vedic period. This means that the core vedic period was potentially 1) spatially disconnected from the paravedic IVC and 2) in part temporally disconnected too. This punctures the pet R^iveda well after IVC hypothesis of the mainstream Indologist (as an aside).