DSDP Explanatory Notes 4/87 EXPLANATORY NOTES ================= TABLE OF CONTENTS A. DEFINITION OF LEG,SITE,HOLE CORE,SECTION B. METHOD OF SAMPLE LABELING C. DESIGNATIONS FOR SPECIAL CORE TYPES D. FORMULA USED FOR ABSOLUTE DEPTH CALCULATIONS OF SAMPLES A. DEFINITION OF LEG,SITE,HOLE,CORE,SECTION LEG NUMBER: LEG was the term used by the Deep Sea Drilling Project to define a cruise of the Glomar Challenger. A leg normally lasted 8 weeks and usually was directed toward solving geologic problems in a specific ocean area. SITE: A location, defined by latitude and longitude, where a positioning beacon was dropped. HOLE: Each new penetration of the sediment/water interface at a site defined a HOLE. All holes drilled using the same positioning beacon were considered to be part of the same site. The first hole drilled at a site is identified by the site number alone. Additional holes are identified by the site number followed by a letter (A,B,C,..etc.). CORE: A core number was designated each time the core barrel made a trip through the drill string and drilling was done. The cores are numbered consecutively, beginning with 1. A core barrel recovered empty after drilling is still considered a core. Section C of the explanatory notes outlines the special core types and their designations. SECTION: During the first 46 legs of drilling, sections were labeled consecutively, with the first section at the top of the core and the sixth at the bottom. However,the sections were measured from the bottom up (i.e. the juncture of the top of the core catcher and the core barrel). Consequently, when recovery was slightly less than 9.2 meters (30 feet) the first section of each core would be less than 150 cms long. When less than 7.5 meters (24.6 ft) of core were recovered, the core could be divided into only five or fewer 150 cm sections, yet the top of a short core would still be labeled section 1. On some occasions more than 9.0 meters were obtained, so that a small remainder, 10- 20 cm long would be left after six sections were cut from a core. This remainder is called section zero, denoting its position above section one. The core catcher section (CC), which is normally 10-15 cm in length, is the material left in the core catcher after the core barrel and core catcher are separated. In the event that there were gaps in the core which resulted in empty sections, these sections were still given numbers in sequence. Diagrammatically this can be explained as follows: Core Cutting and labeling for legs 1-46 CC = Core Catcher, nominally 0.2 meter %% = Recovered material Example 1 : 9.2 meters cored, 9.2 meters recovered, 6 sections and Core Catcher Section 1 |Section 2 |Section 3 |Section 4 |Section 5 |Section 6 |CC ----------|----------|----------|----------|----------|----------|-- %%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% %%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% %%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% ----------|----------|----------|----------|----------|----------|-- 0 1.5 3.0 4.5 6.0 7.5 9.0 Meters from top of core Example 2 : 9.2 meters cored, 9.4 meters recovered 6 sections, Zero Section, and Core Catcher ZZ = Zero Section (NGDC NOTES: 00 also used in data for Zero Section) ZZ|Section 1 |Section 2 |Section 3 |Section 4 |Section 5 |Section 6 |CC --|----------|----------|----------|----------|----------|----------|-- %%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% %%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% %%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% --|----------|----------|----------|----------|----------|----------|-- 0.2 1.7 3.2 4.7 6.2 7.7 9.2 Meters from top of core Example 3 : 9.2 meters cored, 5.2 meters recovered 4 sections and Core Catcher |Section 1 |Section 2 |Section 3 |Section 4 |CC ---------------------|----------|----------|----------|----------|-- empty liner discarded| %%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% | %%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% | %%%|%%%%%%%%%%|%%%%%%%%%%|%%%%%%%%%%|%% ---------------------|----------|----------|----------|----------|-- 0 1.5 3.0 4.5 6.0 Meters from top of core Beginning with leg 47, cores were measured and numbered from the top down. The top of the core was designated as that area where sediment recovery began. Empty core liner was cut off and discarded. The first section became section one and were numbered consecutively to the bottom of the core. Therefore, in theory, the occurrence of a zero section was eliminated and section numbers extended beyond the original maximum of six. In practice, however, on rare occasions, a piece of sediment would be found in the core barrel above the beginning of core. In order to curate the material and place it in its proper relationship to the rest of the core, it was designated as section zero. B. METHOD OF SAMPLE LABELING Samples were numbered before being processed. The numbering system includes a designation for Leg, Site, Hole, Core, Section, Interval within the section. Therefore, sample 56, 534A,10,5,23-24 refers to Leg 56, Site 434, Hole A (second hole drilled at the site-this sequence ennumerated as 434, 434A, 434B etc.,so that the first hole drilled at a site does not have a letter designator),Core 10, Section 5, 23-24 centimeters. C. DESIGNATIONS FOR SPECIAL CORE TYPES Core Type Code Description ===================== ======= ============================= Center bit C The center bit is a device placed in the bottom hole assembly to keep material out of the drill string when no core is desired. This insert has a small orifice and a chamber behind the orifice which collects some cuttings and washings from drilled intervals. Samples from the center bit are labeled C and are assigned consecutive numbers. Their depths correspond to the drilled interval. Drill Bit B Upon completion of a hole and retrieval of the drill string, materials caught within the teeth of the drill bit or splines of the bottom hole assembly were collected and marked B for drill bit sample. Sidewall Sample S The sidewall sampling device is attached to the bottom of the core barrel. Its main purpose is to take small samples of sediment from the side of a hole as the drill string is being raised. Several samples could be obtained from one hole by repeated lowerings of the sample device and progressively raising the drill string to the depth of each sample required. The location of the required sample was judged quite accurately by the length of the drill string. Samples from the sidewall sampler are labeled S and are numbered consecutively within a hole except on Legs 16 and 42 where they are numbered according to their relationship with the drilled cores. Site Survey Cores MP & SP Any core labeled with 2 letters is a site survey core. These were piston cores taken by a vessel other than Challenger then delivered to Challenger unopened so that they could be cut, described, and sampled at the same time as the drilled cores for that site. The piston cores represent the top most layers of sediment which, at the time, could not successfully sampled by Glomar Challenger drilling equipment. Wash Cores H When "washing" down a hole, drilling rates are higher if a core barrel is used rather than blocking the drill bit with a center bit device, even though a core is not desired. Consequently, the driller would "wash" down a hole as many meters as desired without retrieving a core. The material collected in the core barrel represents a melange of the sediments occurring in the washed interval. In-Situ Water Sample W An attempt to extract interstitial water from the mud below the bit using a special tool instead of the standard core barrel. No core was taken; any mud retrieved was scraped from the tool's probe. Misc. Material and/or Drilling Rubble X This represents material that could not be labeled with a standard core number. Gravity Piston Core P Only one gravity piston core was taken from Glomar Challenger. D. FORMULA FOR ABSOLUTE DEPTH CALCULATIONS ZSL= Zero Section Length SECT= Section Number INT= Interval in centimeters within the section LSL= Length of last section (cm) TCD= Depth to top of core (M) LS= Number of last section If sample occurs in: Formula used is: ======================== =========================== Zero section TCD + (INT/100) Sections 1,2,3, etc. TCD + ZSL/100 +(SECT#-1)*1.5 + INT/100 Core Catcher (pre-leg47) TCD + ZSL/100 + LS*1.5 + INT/100 Core Catcher (post-leg47) TCD + ZSL/100 + (LS-1)*1.5 + LSL + INT/100 NOTE: Occasionally no explicit centimeter interval is assigned to a sample taken from within a core catcher. In these cases, a length of 10cm is assigned. DSDP Explanatory Notes 4/87