The Surdarshan Chakra is Lord vishnu's weapon mentioned in many puranas and in Itihasas. But is there any reference of Surdarshana Chakra in Vedic literature (that is Vedas,Upanishads,Brahmans).the wikipedia says in the Rigveda the Chakra was Vishnu's symbol as the wheel of time, so where exactly is Chakra of Lord Vishnu mentioned?
Yes surdarshan chakra was called Vishnu s chakra in ancient texts including RIG Veda and even in valmiki Ramayana it is called Vishnu s Chakra.
He, like a rounded wheel, hath in swift motion set his ninety racing steeds together with the four.Developed, vast in form, with those who sing forth praise, a youth, no more a child, he cometh to our call(Rig veda 1.155.6)
The word Chakra is translated as wheel,even Wikipedia says in Yajurveda vishnu s chakra is mention but till now i could not find a refernce in yajur Veda.