Marbled Chocolate Rye Sourdough

Autolyse 1hour. Mixed in the levain, salt, and any remaining water, then divided the dough in half and incorporated the cocoa powder into one section. Bulk fermented for 4 hours then combined the two doughs during pre-shaping. Let the dough bench rest for 20mins then shaped and placed it into the fridge for a 16 hour cold proof. Scored and baked the next day in a Dutch oven at 500F with the lid on for 15mins, then 450F with the lid off for 20mins.