Chert intervals in DSDP and ODP sites (Table 1), supplement to: Muttoni, Giovanni; Kent, Dennis V (2007): Widespread formation of cherts during the early Eocene climate optimum. Palaeogeography, Palaeoclimatology, Palaeoecology, 253(3-4), 348-362


Radiolarian cherts in the Tethyan realm of Jurassic age were recently interpreted as resulting from high biosiliceous productivity along upwelling zones in subequatorial paleolatitudes the locations of which were confirmed by revised paleomagnetic estimates. However, the widespread occurrence of cherts in the Eocene suggests that cherts may not always be reliable proxies of latitude and upwelling zones. In a new survey of the global spatio-temporal distribution of Cenozoic cherts in Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sediment cores, we found that cherts occur most frequently in the Paleocene and early Eocene, with a peak in occurrences at ~50 Ma that is coincident with the time of highest bottom water temperatures of the early Eocene climatic optimum (EECO) when the global ocean was presumably characterized by reduced upwelling efficiency and biosiliceous productivity. Cherts occur less commonly during the subsequent Eocene global cooling trend. Primary paleoclimatic factors rather than secondary diagenetic processes seem therefore to control chert formation. This timing of peak Eocene chert occurrence, which is supported by detailed stratigraphic correlations, contradicts currently accepted models that involve an initial loading of large amounts of dissolved silica from enhanced weathering and/or volcanism in a supposedly sluggish ocean of the EECO, followed during the subsequent middle Eocene global cooling by more vigorous oceanic circulation and consequent upwelling that made this silica reservoir available for enhanced biosilicification, with the formation of chert as a result of biosilica transformation during diagenesis. Instead, we suggest that basin-basin fractionation by deep-sea circulation could have raised the concentration of EECO dissolved silica especially in the North Atlantic, where an alternative mode of silica burial involving widespread direct precipitation and/or absorption of silica by clay minerals could have been operative in order to maintain balance between silica input and output during the upwelling-deficient conditions of the EECO. Cherts may therefore not always be proxies of biosiliceous productivity associated with latitudinally focused upwelling zones.

Related Identifier
Metadata Access
Creator Muttoni, Giovanni; Kent, Dennis V
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2007
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Language English
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 1296 data points
Discipline Earth System Research
Spatial Coverage (-2.733W, -64.517S, 2.639E, 57.496N); North Atlantic Ocean; Gulf of Mexico/KNOLL; North Atlantic/CONT RISE; South Pacific Ocean; South Atlantic Ocean; South Indian Ridge, South Indian Ocean; Indian Ocean; North Atlantic/CHANNEL; North Atlantic/KNOLL; North Atlantic/BASIN; North Atlantic/BANK; North Atlantic/SEAMOUNT; Caribbean Sea/BASIN; Caribbean Sea/CONT RISE; Caribbean Sea/GAP; Gulf of Guinea; South Pacific/RIDGE; Caribbean Sea; Blake Nose, North Atlantic Ocean; North Pacific/CONT RISE; North Pacific/SLOPE; Great Australian Bight; North Pacific Ocean; Walvis Ridge, Southeast Atlantic Ocean; South Pacific/Tasman Sea/BASIN; South Pacific/Tasman Sea/CONT RISE; South Pacific/Coral Sea/PLATEAU; Indian Ocean//RIDGE; Indian Ocean/Arabian Sea/RIDGE; Indian Ocean//PLATEAU; Antarctic Ocean/CONT RISE; North Pacific/Philippine Sea/CONT RISE; North Pacific/BASIN; North Pacific; South Pacific/PLATEAU; South Atlantic/PLATEAU; North Atlantic/RIDGE; North Atlantic; North Atlantic/PLATEAU; North Pacific/HILL; North Pacific/Gulf of California/CONT RISE; South Atlantic/CONT RISE; South Atlantic/RIDGE; North Pacific/PLAIN; South Pacific; North Atlantic/SLOPE
Temporal Coverage Begin 1968-12-03T00:00:00Z
Temporal Coverage End 2003-04-15T00:00:00Z