Complex sentence: Its geologic evolution begins in the mid Eocene and involves phases of extension and rifting, thermal sag, and isostatic subsidence then rapid, high volume sedimentation related to uplift and inversion beginning in the Early Miocene.
Split into simpler sentences: Its geologic evolution begins in the mid Eocene and involves phases of extension and rifting, thermal sag, and isostatic subsidence. Rapid, high volume, sedimentation related to uplift and inversion began in the Early Miocene.