～だけでなく（て）　ｖｓ　～だけでわなく（て）

My textbook introduced the structure ～だけでなく（て）、～も. It explains that you can either say ～だけでなく（て）or ～だけじゃなく（て）. The latter being more conversational. However, I'm curious as to where でなく（て）comes from. I'm guessing it comes from ではない, but the textbook doesn't mention that. Is the following a valid sentence?

この地方は名物だけではなくて、気候でも知られていま す。

Thank you!

The etymology is the same between the two expressions. It's a negative of the copula だ.

Your sentence is understandable enough, but grammatically it should be この地方は名物でだけではなくて、気候でも（よく）知られています/有名です。 or この地方は名物だけではなくて、気候も（よく）知られています/有名です。