- © The Society of Canadian Petroleum Geologists
Intertidal-supratidal couplets of the Yahatinda Formation were affected by pedogenic, meteoric and phreatic processes. These dolostone and terrigenous dolostone couplets represent paleosol chronosequences that show no systematic upward or downward change in paleosol maturity or thickness based on sedimentologic, pedologic, geochemical and isotopic evidence. In contrast to idealized sequence stratigraphic models, the thickest intertidal-supratidal couplet contains the most mature paleosols. Geochemical paleosol signatures appear to be less related to paleosol maturity than to high soil alkalinity, the amount of sediment delivered during pedogenesis and the effects of exposure to both meteoric and phreatic conditions during shallow burial. At the top of the section, shallow marine shales are capped by a brecciated calcrete-dolocrete hardpan that represent submarine and subaerial hiatuses, respectively. Based on estimates of modern hardpan development, a time constraint of 20–400 thousand years is placed on the unconformity at the top of the Yahatinda Formation.