The Nature of Viññāṇa as a Nidāna in the Cycle of Paṭiccasamuppāda

In the cycle of paṭiccasamuppāda, if we start from avijjā, the next nidāna is that of saṅkhāra which in turn conditions the origin of viññāṇa, loosely termed as consciousness. This viññāṇa in turn conditions the appearance of nāmarūpa, followed by saḷāyatana, the six sense bases. This as all of us know is followed by phassa and then the rest of the twelve nidānas. Now my question is: what is the nature of this viññāṇa, this consciousness, that appears anterior to nāmarūpa, name and form, and, saḷāyatana, the six sense bases? As I understand this, the body and the mind as well as the six sense bases have not appeared as yet at this step of the cycle, and therefore, this viññāṇa cannot be said to be one of the six sense consciousnesses; then what is the content of this ‘primordial’ consciousness? Is it the saṅkhāra-generated bhavaṅga citta, or is it something else?