Terrestrial RocksThe lack of evidence of tillites and associated glacial deposits, which are the best indicators of cold climates, suggests a warm Late Cretaceous climate. This is supported by the high sea level at the time, which implies the absence of polar ice sheets.
Further evidence are the substantial evaporite deposits in the Late Cretaceous. Evaporites signify a persistent excess of evaporation over precipitation and occur in subtropical climates.
Marine RocksIn the Late Cretaceous, sea level was up to 200 m higher than it is at present. Due to this, the continents were well dispersed and marine sediments were forming in abundance. The Late Cretaceous is therefore characterised by marine deposits such as:
The chalk productivity essentially stopped at the end of the Maastrichtian as a result of the KT extinction. The onset of clay deposition and possibly low oxygenation at the sea floor caused the geologically instantaneous destruction of these marine habitats.