Paleosol caliche in the New Haven Arkose, Newark Group, Connecticut
Abstract The New Haven Arkose is a 1500–2500 m sequence of fluvial red beds of Late Triassic and probably Early Jurassic age that accumulated in a tropical rift valley. Streams flowing from highlands along the valley deposited braided channel sand interbedded with overbank mud. At most outcrops in Connecticut, some of the beds of red mudstone and sandstone contain paleosol caliche with densely packed root casts and rhizoconcretions. These calcified mudstones and sandstones commonly show the initial stages of calcification where subspherical to vertically elongate calcite nodules with crystic plasmic (microspar) fabric replace up to 50% of the host rock. In more mature paleosols, coalescing calcite nodules replace 50–95% of the rock, accompanied by paleosol mosaics of pedotubules, peds, and laminated crystallaria. The best developed caliche profiles are capped by thin (0–10 cm) layers of nearly pure limestone with complex fabrics of nodules, microspar, veins, caliche clasts, laminae, and calcite cement. The caliche profiles accumulated when rates of sedimentation were low. Much of the time the tropical paleoclimate was semiarid, perhaps with 100–500 mm of seasonal rain and a long dry season.