The LDE is believed to have been approximately 170-230 kyr in duration and occurred about 62.18 Ma.[1] The LDE consisted of two distinct δ13C excursions, which are referred to as LDE1 and LDE2, respectively.[2]
Effects
The LDE was similar in essence to the Palaeocene-Eocene Thermal Maximum (PETM), although significantly smaller in magnitude.[3][4] Seawater warmed by about 2-3 °C in both the surface oceans and the deep oceans.[5] The LDE led to a significant shoaling of the oceanic lysocline, which is evidenced by the greatly reduced calcium carbonate preservation that occurred during the event.[6] Significant black shale deposition occurred during the LDE, a consequence of sea level rise and clastic starvation combined with enhanced nutrient input into the ocean and anoxia.[7]
The planktonic foraminifergenusMorozovella, especially the speciesM. angulata, increased in abundance.[8] Sediment core analysis from Shatsky Rise shows that 40 kyr before LDE1, an increase in phytodetritus occurred, increasing the abundance of the benthic foraminifer Tappanina selmensis. The start of LDE1 brought about oligotrophic conditions on the seafloor, which continued through LDE2.[2] Unlike the PETM, the LDE did not result in an extinction of benthic foraminifera.[1]
Comparisons with present global warming
As the first global hyperthermal event of the Cenozoicera, the LDE has been interpreted as analogous to present-day anthropogenic global warming. Based on what happened during the LDE, researchers predict the immediate future, in geologic terms, will be characterised by significant ocean acidification and enhanced atmospheric circulation creating a smaller latitudinal temperature gradient.[9]
