doubt regarding oil shale geology hi there i just wanted a clarification regarding one theory supposes that the organic material in the irati oil shale originates from algae deposited in a freshwater to brackish lacustrine environment in the above sentence what does the phrase freshwater to brackish lacustrine environment mean does it mean oil shale originates from algae deposited in a freshwater environment or does it mean oil shale originates from algae deposited in a brackish lacustrine environment or does it mean something else