Intern:Age

In its initial concept, PANGAEA was designed to archive data from geoscientific, in particular paleoclimate research. Thus in addition to the spatial geo-codes, the system obtained a time geocode to map all data versus time on a common age scale. This enables the user to extract time slices with ART or Pan2Applic from an individual subset of data extracted from the system. Also different types of paleorecords might be combined and plotted versus one common time axis: see the multi proxy example from corals, ice, sun spots and reconstructed sea surface temperatures at. This chapter may help in archiving any kind of ages related to geological records.

To obtain the age of a geological profile usualy three steps are required:
 * 1) The profile needs to be dated at some points with one of the various age determination methods.
 * 2) A selection of dated points (stratigraphic fixpoints) forms the age model. (Any data from geological profiles should be accompanied by its age model.)
 * 3) The ages for the complete profile and each single sampling/measurement point is calculated by interpolation between fixpoints.

From the parameter dictionary a list of parameters required for the import of ages can be retrieved.

--- ! NOTE ! ---
 * All age parameter have the unit kiloyears [ka] !
 * The parameter Age, calculated is used in conjunction with the Advanced Retrieval Tool (ART) only. It is exclusively used by the system to dynamically calculate/interpolate ages between stratigraphic fixpoints of an age model during a retrieval with ART. DO NOT USE FOR 4D IMPORT !
 * Age [Ma] is used for standards only
 * Age determinations and age models should be archived as one dataset per profile. Do not mix several cores in one dataset!



ad (1) Each sample, used for age determinations has one mean depth supplemented mostly by two depth, defining the upper and lower boundary of the sampled horizon. An import table for datings should include (ID in brackets): For each age determination a confidence level and comments may be added: If data are provided versus year A.D. (anno domini) or in counted years (e.g. varves, growth bands, tree rings), the original year-values remain in the parameter If 14C radiocarbon age datings are archived:
 * Depth [m] (1)
 * Depth min [m] (3)
 * Depth max [m] (4)
 * Age, dated [ka] (5506) (always provide the method with this parameter!)
 * Age, min [ka] (UCL, upper confidence level, 6170)
 * Age, max [ka] (LCL, lower confidence level, 6169) or just
 * Age, dated standard deviation (6165).
 * Age, dated material (2836) is a text parameter to add a description of the material which was used for the age determination.
 * Age, comment (643) may be used for any dating-related comments.
 * Year [a A.D.] (2936), might also be used with decimal fractions, e.g. 1955.67
 * specify the calibration used for converting 14C-years to calendar years in the method (e.g. INTCAL)
 * specify the reservoir correction used for marine 14C dates (4905 in years!)

ad (2) Following the scientific decision, which age determinations are usefull, an age model is defined. It consists of a table of stratigraphic fixpoints with To precisely define the upper and lower limit of an age, the system provides the parameters
 * Age model [ka] (6) (should always be related to the method used)
 * Age model, optional [ka] (6666) may be used if more age models exist
 * Age, comment (643); this text parameter may contain information about each stratigraphic fixpoint.
 * Age, minimum/young (6167), numeric parameter
 * Age, maximum/old (6168), numeric parameter
 * Age from (oldest) (45397), text parameter
 * Age to (youngest) (45398), text parameter

A Hiatus is defined by using its depth twice with the upper and lower time limit of the hiatus.

Example of an age model ready for import
ad (3) From the age model, the ages of the distinct samples are calculated by various interpolation methods. In a resulting data set an age is given for each sampling point which is imported as geocode The following parameters may be used if a calendar age is explicitly given The geocode AGE and the geocode DEPTH can be used simultaneously
 * AGE [ka] (2205); this is the common internal time scale of all geological data in the system (synthetic time axis after Negendank).
 * Calendar years [ka BP] (14698)
 * Calendar years, standard deviation (15362)