Halite fluid inclusions and the late Aptian sea surface temperatures of the Congo Basin, northern South Atlantic Ocean

Abstract

The Aptian stage represents a pivotal transition of the Cretaceous climate of the Earth but a comprehensive picture of the climate conditions is still unavailable due to the fragmentary paleotemperature records of the mid-late Aptian interval, especially in the Central Segment of South Atlantic region In this region extensive and thick salt sequence severely limiting the applicability of traditionally used paleotemperature proxies. In this paper, we present new quantitative sea surface temperatures from Congo Basin, during the late Aptian based on homogenization temperatures (Th) of fluid inclusions of halite. Homogenization temperatures concentrated at 25–35 °C are consistent with previous climate model results and represent the prevailing sea surface temperatures in the Congo Basin. The derived maximum sea surface temperature is 46.5 °C and much higher than existing paleotemperature records for the late Aptian, apparently representing local hot climate conditions. However, it is comparable with temperature records from many ancient and modern evaporitic basins where potash deposits also largely developed as seen in the Congo Basin. Significant cooling by about 5 °C was identified by both maximum (ThMax) and average (ThAverage) homogenization temperatures of halite during the late Aptian. A comparison of our results with records from other places leads to the conclusion that the observed declining sea surface temperatures of the Congo Basin represent the regional response to global climate cooling in the late Aptian. However, the amplitude, short-term oscillation pattern and worldwide correlation of this cooling is still difficult to assess due to often imprecise and poorly resolved age data, emphasizing the need of better constraint chronologies. Homogenization temperatures of halite fluid inclusions demonstrate the potential of the method to reliably track environmental and climatic changes of the past, especially in evaporitic settings of the Phanerozoic where other climate proxies are often not available.