What was the market cap of Bitcoin before and after the Bitcoin Cash fork? I'm trying to understand the mechanics of the hard fork that created the Bitcoin Cash blockchain on August 1, 2017. After the fork, each holder of BTC got the same amount of BCH as they had BTC.

My question is around what happened to the market cap of BTC as BCH emerged. Specifically, what was the aggregate market value of all BTC immediately prior to the fork and then immediately after. 

I've tried looking for this in different forums, but can't find a reliable source.
On 31 July 2017 Bitcoin had 51.48% of total market cap.

On 1 August 2017 Bitcoin had 43.04% of total market cap where as Bitcoin Cash had 10.77% of total market cap.

For more information about market cap https://coinmarketcap.com/charts/