Publication Date:
2024-01-19
Description:
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.
Keywords:
101-626; 101-627; 101-628; 101-634; 101-635; 10-96_Site; 11-106_Site; 112-682; 113-689; 114-698; 114-700; 114-702; 114-703; 115-706; 115-707; 119-738; 11-98_Site; 120-748; 120-749; 120-750; 12-111_Site; 12-116_Site; 12-117_Site; 12-119_Site; 121-752; 121-758; 122-761; 122-762; 123-765; 15-146_Site; 15-152_Site; 15-153_Site; 159-959; 159-960; 159-961; 16-157_Site; 165-1001; 171-1049; 171-1050; 171-1052; 17-167_Site; 177-1090; 177-1094; 18-173_Site; 182-1126; 182-1128; 182-1129; 182-1130; 182-1131; 182-1132; 182-1133; 182-1134; 183-1135; 183-1136; 192-1183; 192-1186; 199-1216; 199-1217; 199-1218; 199-1220; 199-1221; 199-1222; 206-1256; 208-1265; 21-206_Site; 21-207_Site; 21-208_Site; 21-209_Site; 22-217_Site; 23-219_Site; 28-264_Site; 28-268_Site; 31-292_Site; 3-13_Site; 32-313_Site; 33-316_Site; 33-317_Site; 33-318_Site; 39-356_Site; 41-366_Site; 41-370_Site; 43-384_Site; 43-386_Site; 43-387_Site; 44-390_Site; 47-397_Site; 48-404_Site; 48-405_Site; 50-416_Site; 5-33_Site; 57-438_Site; 61-462_Site; 62-465_Site; 63-473_Site; 72-516_Site; 75-530_Site; 79-547_Site; 81-552_Site; 8-70_Site; 8-71_Site; 8-73_Site; 89-585_Site; 95-612_Site; 95-613_Site; AGE; Age, maximum/old; Age, minimum/young; Antarctic Ocean/CONT RISE; Area/locality; Biozone; Blake Nose, North Atlantic Ocean; Caribbean Sea; Caribbean Sea/BASIN; Caribbean Sea/CONT RISE; Caribbean Sea/GAP; Comment; COMPCORE; Composite Core; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; Duration; Elevation of event; Event label; Glomar Challenger; Great Australian Bight; Gulf of Guinea; Gulf of Mexico/KNOLL; Indian Ocean; Indian Ocean//PLATEAU; Indian Ocean//RIDGE; Indian Ocean/Arabian Sea/RIDGE; ISL.B; Island_Beach_Site; Joides Resolution; Latitude of event; Leg10; Leg101; Leg11; Leg112; Leg113; Leg114; Leg115; Leg119; Leg12; Leg120; Leg121; Leg122; Leg123; Leg15; Leg150X; Leg159; Leg16; Leg165; Leg17; Leg171B; Leg177; Leg18; Leg182; Leg183; Leg192; Leg199; Leg206; Leg208; Leg21; Leg22; Leg23; Leg28; Leg3; Leg31; Leg32; Leg33; Leg39; Leg41; Leg43; Leg44; Leg47; Leg48; Leg5; Leg50; Leg57; Leg61; Leg62; Leg63; Leg72; Leg75; Leg79; Leg8; Leg81; Leg89; Leg95; Longitude of event; North Atlantic; North Atlantic/BANK; North Atlantic/BASIN; North Atlantic/CHANNEL; North Atlantic/CONT RISE; North Atlantic/KNOLL; North Atlantic/PLATEAU; North Atlantic/RIDGE; North Atlantic/SEAMOUNT; North Atlantic/SLOPE; North Pacific; North Pacific/BASIN; North Pacific/CONT RISE; North Pacific/Gulf of California/CONT RISE; North Pacific/HILL; North Pacific/Philippine Sea/CONT RISE; North Pacific/PLAIN; North Pacific/SLOPE; North Pacific Ocean; Ocean Drilling Program; ODP; Paleolatitude; Paleolongitude; South Atlantic/CONT RISE; South Atlantic/PLATEAU; South Atlantic/RIDGE; South Atlantic Ocean; South Indian Ridge, South Indian Ocean; South Pacific; South Pacific/Coral Sea/PLATEAU; South Pacific/PLATEAU; South Pacific/RIDGE; South Pacific/Tasman Sea/BASIN; South Pacific/Tasman Sea/CONT RISE; South Pacific Ocean; Walvis Ridge, Southeast Atlantic Ocean
Type:
Dataset
Format:
text/tab-separated-values, 1296 data points
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