For 2.2–3.2 Ma, the Site U1308 RPI record is compared with a RPI record from North Atlantic IODP Site U1314, and with the Pacific Epapis stack.
The mean sedimentation rates of the North Atlantic sites in NARPI-2200 are greater (by about an order of magnitude) than most of the records incorporated in other stacks.
Any feature, including colour variations, textures, fossil content, mineralogy, or any unusual combinations of these can be used.
It is only by correlations that the conditions on different parts of Earth at any particular stage in its history can be deduced.
Radiometric dating and certain other approaches are used to provide absolute chronologies in terms of years before the present.
In addition, they have had to develop special techniques with which to dissolve these highly refractory minerals without contaminating the small amount (about one-billionth of a gram) of contained lead and uranium on which the age must be calculated.To date past events, processes, formations, and fossil organisms, geologists employ a variety of techniques.These include some that establish a relative chronology in which occurrences can be placed in the correct sequence relative to one another or to some known succession of events.The age model was built by correlation of the benthic oxygen isotope record to a global stack (LR04).Apart from the expected polarity reversals, three magnetic excursions are recorded: Punaruu in MIS 31/32 at 1092 ka, Gilsa in MIS 54/55 at 1584 ka, and a newly recognized excursion labeled Porcupine (after the nearby Porcupine Abyssal Plain) in MIS G6/G7 at 2737 ka.