In northern East Africa, water levels dropped rapidly about 5,500 years ago while in Hoti cave in Arabia a southward retreat of the Indian Monsoon took place about 5,900 years ago. Drying is also documented from Oman, nd rivers and lakes of Arabia became intermittent or entirely dry. The Blue Nile basin became less moist with a noticeable decrease of Nile discharge about 4,000 years ago. Decreased discharge of the Nile led to the cessation of sapropel deposition and turbidite activity off its delta.