Organic matter production and preservation in the Lusitanian Basin (Portugal) and Pliensbachian climatic hot snaps

Worldwide preservation of organic matter during the Late Pliensbachian seems to have resulted in decreased atmospheric CO2 levels through geological storage of carbon, triggering and/or amplifying the Spinatum Chronozone icehouse event. Ultimately, this cooling event may have led to the occurrence of permafrost and/or methane gas hydrates in locations easily disturbed by the subsequent Early Toarcian warming, or/and volcanic activity driven by crustal unloading due to deglaciation.