Misinformation may arise during core description and analysis unless due attention is paid to common disturbances caused by the piston-coring mechanism. Some mid-core flow-in features can resemble slump bedding. Sandy sediment commonly migrates along the core margins as a sand—water slurry; voids are left by its removal and entirely new beds formed by its intrusion. Inclined laminae, rotated blocks and minor faults may be secondary sedimentary features caused by slumping, or artefacts of the piston-coring process. Core rotation of up to 100° has been detected by palaeomagnetic study. Variable lengths are usually missing from the upper sections of piston cores; estimation of deposition rates for the most recent sediment is therefore hazardous.