1 research outputs found
Three distinct Holocene intervals of stalagmite deposition and nondeposition revealed in NW Madagascar, and their paleoclimate implications
Petrographic features, mineralogy, and stable isotopes from two stalagmites,
ANJB-2 and MAJ-5, respectively from Anjohibe and Anjokipoty caves, allow
distinction of three intervals of the Holocene in NW Madagascar. The
Malagasy early Holocene (between ca. 9.8 and 7.8 ka) and late Holocene
(after ca. 1.6 ka) intervals (MEHI and MLHI, respectively) record evidence of stalagmite
deposition. The Malagasy middle Holocene interval (MMHI, between ca. 7.8 and 1.6 ka)
is marked by a depositional hiatus of ca. 6500Â years.
Deposition of these stalagmites indicates that the two caves were
sufficiently supplied with water to allow stalagmite formation. This
suggests that the MEHI and MLHI intervals may have been comparatively wet in
NW Madagascar. In contrast, the long-term depositional hiatus during the
MMHI implies it was relatively drier than the MEHI and the MLHI.
The alternating wet–dry–wet conditions during the Holocene may have been
linked to the long-term migrations of the Intertropical Convergence Zone
(ITCZ). When the ITCZ's mean position is farther south, NW Madagascar
experiences wetter conditions, such as during the MEHI and MLHI, and when it
moves north, NW Madagascar climate becomes drier, such as during the MMHI. A
similar wet–dry–wet succession during the Holocene has been reported in
neighboring locations, such as southeastern Africa. Beyond these three
subdivisions, the records also suggest wet conditions around the cold 8.2 ka
event, suggesting a causal relationship. However, additional Southern
Hemisphere high-resolution data will be needed to confirm this