Ls. Land et Fl. Lynch, DELTA-O-18 VALUES OF MUDROCKS - MORE EVIDENCE FOR AN O-18-BUFFERED OCEAN, Geochimica et cosmochimica acta, 60(17), 1996, pp. 3347-3352
The whole-rock delta(18)O of mudrocks, as well as the delta(18)O of th
e clay-sized silicate fraction, does not change in any systematic mann
er over Paleozoic and late Proterozoic time. Therefore, the delta(18)O
of the ocean has not changed (except a per mil or so as the result of
glaciation/deglaciation) over the last billion years of Earth history
.