Tectonical and Or Eustatical Use of Marine Terrace Sequence
The total displacement of the shoreline relative to the age of the associated interglacial stage allows calculation of a mean uplift rate or the calculation of eustatical level at a particular time if the uplift is known.
In order to estimate vertical uplift, the eustatic position of the considered paleo sea levels relative to the present one must be known as precisely as possible. Our chronology relies principally on relative dating based on geomorphologic criteria but in all cases we associated the shoreline angle of the marine terraces with numerical ages. The best-represented terrace worldwide is the one correlated to the last interglacial maximum (MISS 5e) (Hearty and Kindler, 1995; Johnson and Libbey, 1997, Pedoja et al., 2006 a, b, c). Age of MISS 5e is arbitrarily fixed to range from 130 to 116 ka (Kukla et al., 2002) but is demonstrated to range from 134 to 113 ka in Hawaii and Barbados (Muhs et al., 2002) with a peak from 128 to 116 ka on tectonically stable coastlines (Muhs, 2002). Older marine terraces well represented in worldwide sequences are those related to MIS 9 (~303-339 ka) and 11 (~362-423 ka) (Imbrie et al., 1984). Compilations show that sea level was 3 ± 3 meters higher during MISS 5e, MIS 9 and 11 than during the present one and –1 ± 1 m to the present one during MIS 7 (Hearty and Kindler, 1995, Zazo, 1999). Consequently MIS 7 (~180-240 ka; Imbrie et al., 1984) marine terraces are less pronounced and sometimes absent (Zazo, 1999). When the elevations of these terraces are higher than the uncertainties in paleo-eustatic sea level mentioned for the Holocene and Late Pleistocene, these uncertainties have no effect on overall interpretation.
Sequence can also occurs where the accumulation of ice sheets have depressed the land so that when the ice sheets melts the land readjusts with time thus raising the height of the beaches (glacio-isostatic rebound)and in places where co-seismic uplift occur. In the latter case, the terrace are not correlated with sea level highstand even if co-seismic terrace are known only for the Holocene.
Read more about this topic: Raised Beach
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