Publication Date:
2024-03-06
Description:
Using the Late Miocene to Pliocene organic-walled dinoflagellate cyst record of ODP Site 1081 we reconstruct and discuss the early upwelling history over the Walvis Ridge with a special focus on the movement of the Angola-Benguela Front (ABF). We suggest that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling's filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.3 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Our results indicate a northward migration of the ABF as early as 7 Ma and the initial stepwise intensification of the BUS.
Keywords:
175-1081A; Acomosphaera spp.; AGE; Ataxiodinium confusum; Ataxiodinium zevenboomii; Batiacasphaera hirsuta; Batiacasphaera micropapillata; Benguela Current, South Atlantic Ocean; Brigantedinium spp.; Counting, dinoflagellate cysts; DEPTH, sediment/rock; Dinoflagellate cyst indeterminata; Dinoflagellates, total; DRILL; Drilling/drill rig; Habibacysta tectata; Impagidinium aculeatum; Impagidinium paradoxum; Impagidinium patulum; Impagidinium species 2 after De Schepper & Head (2009); Impagidinium sphaericum; Impagidinium spp.; Impagidinium strialatum; Joides Resolution; Leg175; Lejeunecysta oliva; Lejeunecysta sabrina; Lejeunecysta spp.; Lingulodinium machaerophorum; Marker, added; Marker, found; Nematosphaeropsis labyrinthus; Ocean Drilling Program; ODP; Operculodinium centrocarpum; Operculodinium israelianum; Operculodinium janduchenei; Operculodinium spp.; Pentapharsodinium dalei; Pyxidinopsis reticulata; Quinquecuspis concreta; Sample code/label; Selenopemphix armageddonensis; Selenopemphix brevispinosa; Selenopemphix brevispinosa conspicua; Selenopemphix nephroides; Selenopemphix quanta; Spiniferites cf. mirabilis; Spiniferites membranaceus; Spiniferites mirabilis; Spiniferites ramosus; Spiniferites spp.; Sumatradinium soucouyantiae; Trinovantedinium applanatum; Trinovantedinium ferugnomatum; Trinovantedinium glorianum; Trinovantedinium papula; Tuberculodinium vancampoae; Volume
Type:
Dataset
Format:
text/tab-separated-values, 3408 data points
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