Regional and global context of the Late Cenozoic Langebaanweg (LBW) palaeontological site: West Coast of South Africa

The palaeontological site of Langebaanweg (LBW) is internationally renowned for its prolific, diverse and exceptionally well preserved Mio-Pliocene vertebrate faunas. The site is located on the southern West Coast of South Africa which represents a passive intraplate, trailing edge setting. The southern African subcontinent is also removed from glacial influence and has experienced no Cenozoic volcanic activity. Rates of vertical crustal motion are consequently low and Late Cenozoic shoreline datums at LBW chiefly reflect glacio-eustatic sea level history. The primary aim of this study is to clarify the chronology as well as the regional and global context of LBW and to review previous work on these aspects. LBW is ideally situated to document the complex interactions of ocean, atmosphere and land and their respective influence on climate evolution, given its location near the coast and mix of marine, estuarine and terrestrial faunas and depositional settings. This paper also provides a background to the study of the vast existing faunal collections and a guide to undiscovered fossil deposits. Towards these ends, the first detailed geological/topographic maps of the site and surrounds, accompanied by a summary stratigraphic column are provided. Virtual geological modelling using a subsurface database has clarified the spatial and temporal relationships of sedimentary facies, as well as their depositional settings. ological and palaeontological record at LBW tracks and documents the major regional and global climatic/oceanographic events of the Late Cenozoic. During the Oligocene drawdown in sea levels, the landscape was etched by river incision. Fluctuating sea levels of the Neogene periodically reversed the trend from erosion to deposition, preserving contemporary faunas and floras in the Oligocene palaeovalleys. Earlier Miocene pollen from fluvial facies indicates a humid sub-tropical climate, reflecting a warm southern Atlantic Ocean. The abrupt late Middle Miocene global cooling (Monterey Excursion) coincided with intensified cold upwelling in the Benguela Current and extensive phosphate authigenesis. A globally documented Early Pliocene highstand possibly related to the shoaling of the Isthmus of Panama reached ~ 90 m above sea level (asl), implying extensive melting of the cryosphere. Palaeomagnetic data in tandem with global sea level reconstructions suggested an age of ~ 5.15 ± 0.1 Ma for the faunas and a correlation with the earlier part of this transgression. A subtropical C3 vegetation is indicated by the faunas and floras, but with a significant contribution by sclerophytic fynbos pointing to a cooler and more seasonal climate than in the Miocene. A mid-Pliocene highstand to ~ 50 m asl truncated the Early Pliocene succession at LBW and the globally documented Late Pliocene highstand to ~ 30 m asl saw the Atlantic shoreline approaching LBW for the last time. With the progressive climatic cooling and instability of the terminal Pliocene, culminating in the growth of the Arctic ice cap, strengthening southerly winds driven by a tighter coiled South Atlantic Anticyclone deposited extensive coastal dune fields over the region.