Barth on creatio ex nihilo

It is sometimes debated whether science and Genesis 1 is consistent with the Christian doctrine of creatio ex nihilo [creation out of nothing].

I found it interesting to see what Karl Barth says in the context of his exegesis of Genesis

It is clear enough that there is a chaos; that creation is "somehow" related to it; that it plays its part even in the later history which begins with creation; and that there too there are definite encounters between it and God. But there is no such thing as a "reality of chaos" independently confronting the Creator and His works, and able in its own power as matter or a hostile principle to oppose His operations. 

It may well be that the concept of a creatio ex nihilo, of which there is no actual hint in Gen. 1-2, is the construct of later attempts at more precise formulation. But its antithesis - the mythological acceptance of a primeval reality independent of God - is excluded in practice by the general tenor of the passage as well as its position within the biblical context.

Karl Barth, Church Dogmatics 3.1: The Doctrine of Creation, page 103.

Hence, Barth argues that creatio ex nihilo is not explicitly supported by Genesis. However, he stresses that Genesis stands in conflict with its antithesis.