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钙壳(Caliches)是一种粉末状——胶结完好的低镁方解石沉积物,含少量石英粉砂及粘土矿物,通常呈乳白色或淡黄色。钙壳是在陆地表面或渗流带中,经成土作用而成。形成这类沉积物的母岩通常是碳酸盐岩,但其他沉积岩,甚至火成岩和变质岩(Seneniuk and Searle,1985)也可作为钙壳的母岩。钙壳的地质时代分布广,从前寒武纪至今均有报道,但以更新世和全新世的研究较多,而更新世以前的相对较少。本文以山东平邑盆地下第三系官庄组二段中钙壳为例,探讨其岩石学及生物化石特征、沉积环境和地层意义。
Caliches is a powdered - well-cemented, low-magnesium calcite deposit containing a small amount of quartz sand and clay minerals, usually milky white or light yellow. Calcium shells in the land surface or seepage zone, formed by the role of soil. The parent rocks that form this type of sediment are usually carbonate rocks, but other sedimentary rocks, and even igneous and metamorphic rocks (Seneniuk and Searle, 1985) can also be used as the parent rock for calcium hulls. The geologic age of calcium hulls is widely distributed and has been reported from the Precambrian to the present. However, there are more studies on the Pleistocene and Holocene, but relatively less on the Pleistocene. In this paper, we take the Ca2 + shell in the second member of Guzhuang Formation in the Lower Tertiary of Pingyi Basin, Shandong Province as an example to discuss its petrological and biofossil characteristics, sedimentary environment and stratigraphic significance.