PEDOLOGICAL NODULES WITH CONE IN CONE STRUCTURE IN THE PERMIAN OF SIERRA MORENA (SPAIN) AND CENTRAL MOROCCO

The occurrence of (1) calcite aureoled quartz, and (2) vertical cylindrical features (''rhizocretions'' in literature), and subspherical or unevenly shaped nodules resulting from the coalescence of smaller elements (''nodular calcrete'') is reported in various Permian continental series from Western Europe (Sierra Morena, Spain) and North Africa (Central Meseta of Morocco). These features are developed in flood plain pelites (mudstones) interbedded with gravelly channel material and debris flow deposits. These nodules are interpreted as pedological concretions formed in hydromorphic soils under tropical climatic conditions with contrasting seasons and not under desertic environments. These nodules show the close association of a classical micritic/microsparitic internal sediment with areas where cone in cone structures prevail. The distribution of facies suggests an early pedogenic origin. At this early stage, vegetal roots were alive (probably Cordaitales) and were encrusted by the redistribution of calcite components in the soil profile resulting from oscillations of the water table. The cone-in-cone structure probably resulted from bacterial activity.