Hello there! 

I'm new to this forum, and I'd just like to ask what could have possible happened to my loaf cake

When I slice the cake you can clearly see a separation within the cake, like an upper layer where the crumb is loser and where all the alcohol taste and butter taste is and lower layer where it's just a little more dense and lighter in color. So it seems to have done its own separation while baking. 

The original recipe called for 1/4c + 3 T oil and 1/4c butter but I decided to make it 1/2c butter and 3T oil . Also it's a butter rum loaf, so it called for 1/4c + 2T rum. 

Help please! 

Thank you :)