How marine seeps occur
A marine hydrocarbon seep occurs when fluids containing both dissolved and mixed chemical species ultimately derived from either the breakdown of organic matter in the upper sediments or from deep hydrocarbon reservoirs upwell through the sediment column and potentially into the water column.
These fluids are chemically and/or physically (i.e. temperature) different from bottom seawater. When the upwelling fluids encounter seawater, typically at some depth below the seafloor but also at the seabed for vigorously venting seeps, this zone of mixing involves chemical gradients between the reduced seep fluids and the oxidized seawater.
