Is "which" a preposition? Because because

Backstory: Back in 2013 the American Dialect Society appointed because Word of the Year. People had begun using a new syntax: noun-phrases and adjectives could now follow because. In response Geoffrey Pullum on the Language Log corrected all dictionaries everywhere and argued that because is not a conjunction but a preposition. With this new usage because has not changed or added to its part-of-speech. It is simply acting ever more like the preposition that it is.

That's all old news. Recently I saw a similar use of which:

The earth was formless and empty, and darkness was hovering over the surface of the deep, which, ugh. (Source.)

Simply by rules of analogy, would this usage make which a preposition as well?

*6/29/17 Edit:

I've found another sighting:

That was it. I walked out (no one clapped, which, fair), and for the next half hour I sat in the quiet dark, as three more people took their turns. I peeked through the curtain a few times. One person was lying down. Another was just sitting there.

Solution 1:

No. In this sentence, it's possible your punctution is incorrect.

The sentence is really:

"The earth was formless and empty, and darkness was hovering over the surface of the deep, which... ugh."

It is a truncated sentence, followed by an expression. The which was about to be a pronoun (as in "which [the earth and its form] makes me feel sick"), but the speaker failed to finish their sentence and instead uttered an expression of disgust. This is not the same as "because bacon".