Proc. IODP, 318, Methods

Table T1. IODP depth scale terminology. (See table notes.)

Depth scale name	Acronym	Origin	Method description	Submethod	Unit	Previous name	Previous unit
Drillers depth scale
Drilling depth below rig floor	DRF	Drill floor	Add the lengths of all drill string components deployed beneath the rig floor, from bit to the point on the rig floor where the length of the deployed portion of the last string is measured.	Describe submethod of measuring drill string component length and length deployed at rig floor	m	Depth	mbrf
Drilling depth below seafloor	DSF	Seafloor	Subtract the distance between rig floor and sea level from an estimate of seafloor depth at the drilling depth below rig floor scale using one of the submethods	A. Tag seafloor	m	Depth	mbsf
				B. Mudline core
				C. Visual control
				D. Inherit depth
				E. Other
Core depth scale
Core depth below seafloor	CSF	Seafloor	Measure core sample or measurement offset below the core top and add it to the core top’s drilling depth below seafloor; apply one of the submethods.	A. Let overlap if long	m	Depth	mbsf
				B. Scale if long
				C. Other
Core composite depth	CCSF	Seafloor	Align cores from one hole or multiple adjacent holes based on one of the submethods. The result is a newly constructed depth scale.	A. Append if long	m	Depth	mcd
				B. Scale by factor
				C. Correlate features
				D. Splice
				E. Other
Wireline depth scale
Wireline log depth below rig floor	WRF	Drill floor	Measure length of wireline extended beneath the rig floor.	Describe submethod	m	Depth	mbrf
Wireline log depth below seafloor	WSF	Seafloor	Subtract the distance between rig floor and sea level from an estimate of seafloor depth at the wireline depth below rig floor scale using one of three submethods	A. seafloor signal	m	Depth	mbsf
				B. Drilling depth
				C. Inherit depth
				D. Other
Wireline log speed-corrected depth below seafloor	WSSF	Seafloor	Correction for irregular motion of the tool during logging using accelerometer data; used for high-resolution logs such as microresistivity (FMS).	Describe submethod if applicable	m	Depth	mbsf
Wireline log matched depth below seafloor	WMSF	Seafloor	Pick log data from one run as a reference and map other run data using several tie points.	Describe reference log and number/type of tie points used	m	Depth	mbsf

Notes: Drillers depth scale is based on length of drill pipe lowered below the drill floor. Core depth scale is based on the actual length of core recovered and drillers depth, which can vary with time as core expands or contracts. Core depth is technically not a depth but can be used to derive a depth by cumulating all core lengths. Wireline depth scale is based on the wireline length between the downhole tool and shipboard winch. FMS = Formation MicroScanner. See IODP Depth Scale Terminology at www.iodp.org/program-policies.

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