Until approximately 20,000 years ago the headwaters of the Branco River flowed not into the Amazon, but via the Takutu Graben in the Rupununi area of Guyana towards the Caribbean.
Before roughly 20,000 years ago, the Branco River's source was located in the Takutu Graben of Guyana's Rupununi area and flowed toward the Caribbean instead of the Amazon.