FREEZE CORING

Obtaining a lake-sediment core by means of freezing the sediment to the outside of a tube, box or wedge filled with dry ice (a so-called frozen finger). The device is dropped or lowered into the sediment and pulled out once the sediment has frozen on. It is particularly useful for obtaining an undisturbed sample of delicate sedimentary structures, such as [Page 430]varves, in the uppermost soft sediments, which tend to be disturbed by more conventional chamber or piston samplers during either sampling or transportation or core extrusion.