DSDP Ageprofile 6/86 =============================== = DEEP SEA DRILLING PROJECT = = AGEPROFILE = =============================== I. INTRODUCTION A. BACKGROUND The AGEPROFILE presents age assignments for each DSDP hole as determined by investigators. The term "section" refers to an AGE section not a core section. The data has been selected from one of three sources: the Initial Reports (the blue books), The Initial Core Descriptions or the shipboard site summaries. B. LEGS IN THE DATA SET The data base contains age assignments for legs 1-96. The assigned ages are updated with the publication of each Initial Report. II. FORMAT AND FIELD DESCRIPTIONS A. DATA FORMAT (blank col. 80 removed by NGDC) COLUMN FIELD FORMAT ====== ============================== ====== 1-2 LEG A2 3-5 SITE A3 6 HOLE A1 7-12 AGE MNEMONIC A6 13-18 AUXILIARY AGE MNEMONIC A6 19-24 TOP OF SECTION DEPTH (meters) F6.1 25-30 BOTTOM OF SECTION DEPTH (meters) F6.1 31 SPECIAL CONDITION FLAG ("I","*") A1 32-39 AGE CODE I8 40 space X1 41-48 AUXILIARY AGE CODE I8 49 space X1 50-57 AVERAGED AGE CODE I8 58-62 AGE TOP OF SECTION (million years) F5.0 * 63-67 AGE BOTTOM OF SEC. (million years) F5.0 * 68-72 AVERAGE AGE (million years) F5.0 * 73-79 DATA SOURCE ("IR","ICD","SITESUM") A7 * NGDC NOTE: Data in this field is also given as F5.1 and F5.2. B. FIELD DESCRIPTIONS The definition of leg, site, hole, core and section may be found in the explanatory notes. In addition, the special core designations, as well as the methods of sample labeling and calculating absolute sample depths are discussed. AGE MNEMONIC: An abbreviation of the age name. An auxiliary age is also encoded when it is not possible to determine the precise age for the section. This field is often empty. If two ages are noted, it should not be inferred that they represent ages of the top and bottom of the section. The meaning of a dual assignment is that a precise age determination cannot be made and the age of the section is somewhere in that range. SECTION DEPTH: The subbottom depth in meters to either the top or bottom of the AGE section. SPECIAL CONDITION FLAG: I = A legitimate age inversion * = Missing hole or drilled interval AGE CODE: The age code is an eight digit integer which represents a specific geological age. An age code dictionary is available as a separate file and normally accompanies this data base (see page 5). As in the case of age mnemonic, if a second auxiliary age code is noted, the meaning of the dual assignment is that the precise age is unknown (see explanation under age mnemonic). Averaged age codes consist of a matching of digits from left to right between the age code and auxiliary age code fields. At the first occurrence of a non-matching digit, the averaged age code will be zero filled from that digit through the eighth digit to indicate a lack of precision after that point.* AGE: The assigned age in millions of years that were calculated by one investigator and are not to be considered official DSDP values. They are included for user convenience only. Values were determined for the top and bottom of each section range and their average. The age values may contain one or two decimal places for precision. DATA SOURCE: IR = DSDP Initial Reports ICD = Initial core descriptions SITESUM = Hole summaries *NGDC NOTE: In the SCREEN and Smearslide data bases this convention was not used. An even number was inserted which averaged ages above and below in a given position, digits to the right of the "averaged" even digit were entered as usual. After conferring with Peter Woodbury, the SCREEN data base was modified at NGDC to conform to the conventions described above. AGE CODE DICTIONARY FILE ======================== The age codes are integer values which represent specific geological ages. The construct of the code in eight digits allows immediate recognition of age level (i.e. era, period, epoch, etc.). As an auxiliary file the age code dictionary is necessary for interpreting the age codes present in each record of the age profile data base. The file contains all of the numeric age codes, age names and age mnemonics used by the Deep Sea Drilling Project. AGE CODE FORMAT COLUMN FIELD FORMAT ====== ============================== ====== 1-6 AGE MNEMONIC A6 7-14 AGE CODE I8 15 space X1 16 AGE LEVEL (1-7) I1 17 space X1 18-37 AGE NAME (full name) A20 38-43 *UPPER AGE MNEMONIC A6 44-50 *UPPER AGE CODE I7 51 space X1 52-57 *LOWER AGE MNEMONIC A6 58-64 *LOWER AGE CODE I7 65 space X1 66-70 UPPER AGE (million years) F5.0 73-77 LOWER AGE (million years) F5.0 *NGDC NOTE: These fields are blank-filled. AGE CODE: An eight digit hierarchial code which represents a specific age. The code is designed to provide age level information as outlined below. CODE DIGIT AGE LEVEL ========== ============= 1 (1) ERA 2-3 (2) PERIOD 4 (3) SUBPERIOD 5 (4) EPOCH 6 (5) SUBEPOCH 7 (6) STAGE 8 (7) SUBSTAGE AGE MNEMONIC: An abbreviation of the age name. AGE (million years): The upper and lower absolute age assigned by the DSDP to each geological age. Absolute ages were assigned for internal DSDP use only and may be outdated. NGDC NOTES: (list of deviations from field descriptions) Description of deviation Record Number(s) ======================================= ================ Misplaced decimal in top of section 1587,3104,3297,3542,4555, depth: col 19-24 4911,4936,5130 DSDP Ageprofile 6/86