TY - JOUR
T1 - Disentangling interglacial sea level and global dynamic topography
T2 - Analysis of Madagascar
AU - Stephenson, Simon N.
AU - White, Nicky J.
AU - Li, Tao
AU - Robinson, Laura F.
PY - 2019/8/1
Y1 - 2019/8/1
N2 - Global inventories of stable sea-level markers for the peak of the last interglacial period, Marine Isotopic Stage (MIS) 5e, play a pivotal role in determining sea-level changes and in testing models of glacial isostatic adjustment. Here, we present surveying and radiometric dating results for emergent terraces from northern Madagascar, which is generally regarded as a stable equatorial site. Fossil coral specimens were dated using conventional and open-system corrected uranium series methods. Elevation of the upper (undated) terrace decreases from 33.8 m to 29.5 m over a distance of 35 km. An intermediate terrace has an average radiometric age of 130.7±13.2 ka (i.e. MIS 5e). Its elevation decreases from 9.3 m to 2.8 m over a distance of 80 km. The record of the lowest terrace is fragmentary and consists of beach rock containing rare corals with ages of 1.6–3.8 ka. The spatial gradient of the MIS 5e marker is inconsistent with glacio-isostatic adjustment calculations. Instead, we propose that variable elevations of this marker around Madagascar, and possibly throughout the Indian Ocean, at least partly reflect spatial patterns of dynamic topography generated by sub-plate mantle convection.
AB - Global inventories of stable sea-level markers for the peak of the last interglacial period, Marine Isotopic Stage (MIS) 5e, play a pivotal role in determining sea-level changes and in testing models of glacial isostatic adjustment. Here, we present surveying and radiometric dating results for emergent terraces from northern Madagascar, which is generally regarded as a stable equatorial site. Fossil coral specimens were dated using conventional and open-system corrected uranium series methods. Elevation of the upper (undated) terrace decreases from 33.8 m to 29.5 m over a distance of 35 km. An intermediate terrace has an average radiometric age of 130.7±13.2 ka (i.e. MIS 5e). Its elevation decreases from 9.3 m to 2.8 m over a distance of 80 km. The record of the lowest terrace is fragmentary and consists of beach rock containing rare corals with ages of 1.6–3.8 ka. The spatial gradient of the MIS 5e marker is inconsistent with glacio-isostatic adjustment calculations. Instead, we propose that variable elevations of this marker around Madagascar, and possibly throughout the Indian Ocean, at least partly reflect spatial patterns of dynamic topography generated by sub-plate mantle convection.
KW - dynamic topography
KW - geodynamics
KW - glacial isostatic adjustment
KW - last interglacial period
KW - MIS 5e
KW - sea level
UR - http://www.scopus.com/inward/record.url?scp=85065790298&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2019.04.029
DO - 10.1016/j.epsl.2019.04.029
M3 - Article (Academic Journal)
AN - SCOPUS:85065790298
SN - 0012-821X
VL - 519
SP - 61
EP - 69
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -