The delta area is an important sink for the riverine inputs.The Cs-137 inventory over the studied area (480 km(2)) was estimated to be 19.6 TBq in 1990, of which more than 40% was found in the prodelta (30 km(2)), in the vicinity of the river mouth.Olivier Radakovitch, S Charmasson, M Arnaud, P Bouisset.
Then catastrophic plate tectonics during the Flood stirred the mantle and via partial melting added new rocks to the crust.
These new rocks rapidly accumulated more Pb isotopes due to the concurrent accelerated radioactive decay of U and Th in them during the Flood.
Zircon does incorporate initial Pb when it crystallizes. It cannot be proven that the Pb in apparently cogenetic U- or Th-free minerals is only initial Pb, and that it is identical to the initial Pb in the mineral being dated.
Nor can the measured Pb isotope ratios be used to somehow decide what proportions of them are the initial Pb without recourse to unprovable assumptions about the mineral or rock’s history or their interpreted U-Th-Pb ages within an assumed deep time history.
Its rejection is recognized as fatal to the earth’s claimed age of billions of years.
There is thus no impediment to accepting and using the Bible’s account of Creation and the Flood as a reliable framework for unravelling the history of the earth and the Pb isotopes found in its minerals and rocks.Estuarine, Coastal and Shelf Science, Elsevier, 1999, 48 (1), pp.77-92. U-Pb radioisotope dating is now the absolute dating method of first choice among geochronologists, especially using the mineral zircon.Subsequently new crustal rocks formed via partial melts from the mantle.U decay in those rocks added daughter Pb isotopes to the common or initial Pb isotopes in them, inherited from the rock’s sources.Rates ranged from more than 20 cm year(-1) near the river mouth to 0.2 cm year(-1) on the shelf, decreasing rapidly seawards with a preferential S-SW direction from the mouth in relation to the spreading of surface and bottom nepheloid layers in this area.