Lists and Chains

I am curious about some of the long chains of causes and effects the Buddha lists in the discourses. For instance, in the Discourse on Cause the Buddha lists in the middle of a chain of things 'becoming.' As the causes of becoming he lists attachment, craving, feeling, and so on. How are we to make sense of 1) becoming being caused at all, and 2) things that take place in becoming being cited as a source of becoming. Causes and effects are the processes of becoming; I can't fathom the meaning of the cause of becoming itself. Similarly, in the Greater Discourse on the Destruction of Craving (pg. 64-65) the Buddha lists the four nutriments and one of the causes of the nutriments (contact) is itself a nutriment. Is this an example of dependant arising? If so it is less direct than the dependant arising of consciousness and psycho-physicality, which both directly arise with each other. In this list contact as nutriment and contact as cause are separated by craving and feeling. Does anyone have any suggestions on how to read these lists?