Micromorphological Study of Deep Buried Jurassic Basalt-Derived Paleosols from Northern Israel

An Early Jurassic sequence, the Asher Volcanics, composed of lava flows, 20-30 m thick, interbedded with reddish-brown clayey layers, was penetrated in the Atlit 1 borehole, at a depth interval of 2.9-5.4 km. Results of micromorphological analyses carried out on hand-picked well-cuttings from depths, of 3106, 3378, 3392 and 4189 m suggest that some of the samples represent paleosols. Despite the depth distinct pedogenic features similar to those of modern basalt-derived soil materials, could be recognized. Apparently, younger basalt flows protected the underlying layers, preserving the soil materials. X-ray diffraction showed significant amounts of 2:1 expanding clay minerals, indicating the absence of diagenetic changes. The pedogenic features include clay illuviation, iron-manganese nodules and many iron oxide inclusions within the plasma. Asepic plasmic fabric and craze planes strongly resemble modern soil fabrics. Some samples exhibit strong diagenetic features such as highly striated birefringence of omnisepic fabric. The clayey material in these paleosols presumably was subjected to high stress, though pedogenic indications were not obliterated entirely.