Sibi ruled from the north west of India. There was a Sibi puram on the banks of river Chenab in Punjab. Sibi clan is mentioned in Rig Veda and Brahmanas. Panini referred one Sivapuram may be the same Sibipuram’ Sibi is in Nort west of India, currently in Pakistan.
As the Geological process began 75 million years ago and it took 50 million years for the Drift,it is logical that Ganga was formed around 25 million years ago.
He recites the names of Brahmin Rishis as his ancestors in His Pravara? Why? Lord Rama's Gotra/Pravara is this. ' Yajur vEDa Saakhaa adhyaayinE, VaasishTa, MaitraavruNa KouNDinya trayaarishEya Prvaraanvita, VasishTa....Note how meticulously he uses the term Varma , indicating that He is a Kshatriya. Brahmins must use the term Sarma, Kshatriyas Varma and Vaisyas Gupta after their Names in Pravara.
The Tamil Cholas are referred to as the descendants of Ikshvaku Clan,to which Lord Rama belonged. So the refernce to a temple earlier to that of Srirangam gains credibility. The Temple of Pundarikaksha(Vishnu) is mentioned in Sangam Classics and also referred to in King Rajaraja's inscriptions.