Evaporative systems and diagenetic patterns in the Calatayud Basin (Miocene, central Spain)

Abstract

This paper concerns the evaporite units, depositional systems, cyclicity, diagenetic products and anhydritization patterns of the Calatayud Basin (nonmarine, Miocene, central Spain). In outcrop, the sulphate minerals of these shallow lacustrine evaporites consist of primary and secondary gypsum, the latter originating from the replacement of anhydrite and glauberite. In the evaporative systems of this basin, gypsiferous marshes of low salinity can be distinguished from central, saline lakes of higher salinity. In the gypsiferous marsh facies, the dominant, massive, bioturbated gypsum was partly replaced by synsedimentary chert nodules and siliceous crusts. In the saline lake facies, either cycles of gypsiferous lutite-laminated gypsarenite or irregular alternations of laminated gypsum, nodular and banded glauberite, thenardite and nodular anhydrite precipitated. Early replacement of part of the glauberite by anhydrite also occurred. Episodes of subaerial exposure are represented by:(1) pedogenic carbonates (with nodular magnesite) and gypsiferous crusts composed of poikilitic crystals; and (2) nodular anhydrite, which formed in a sabkha. Additionally, meganodular anhydrite occurs, which presumably precipitated from ascending, highly saline solutions. The timing of anhydritization was mainly controlled by the salinity of the pore solutions, and occurred from the onset of deposition to moderate burial. Locally, a thick (>200 m) sequence of gypsum cycles developed, which was probably controlled by climatic variation. A trend of upward-decreasing salinity is deduced from the base to the top of the evaporite succession.

Sedimentology of the Miocene evaporitic succession in the north of Çankiri-Çorum basin, central Anatolia, Turkey

“…However, selenite and gypsum nodules (initially anhydrite) reflect a saline or hypersaline environment. A type evaporitic system and diagenetic pattern can be commonly established in the sabkha or saline mudflat (Shearman 1966;Orti and Rosell 2000). According to our observations, we can say that the salinity increased upward due to progressive evaporation.…”

“…Carbonate precipitation resulted mainly in the formation of limestones which may be found in the transgressiveevaporitic sequence (Orti and Rosell 2000). According to this interpretation the carbonates indicate that episodes of lake expansion correlate with increasing humidity.…”

“…Nury and Schreiber (1997) pointed out that at the freshwater end of an elongate graben lake there is a brackishwater marsh grading into gypsum beds. Orti and Rosell (2000) also documented gypsiferous marshes with low salinity in the evaporitic-lacustrine system. This environmental type is consistent with the gypsum formation in the organic-rich mudstone of the Cankiri-Corum basin.…”

“…Gypsum nodules are common in the evaporitic-marine and lacustrine environments. Sabkhas or saline mudflats are favorable for their formation or the nodules may be formed as a late diagenetic process (Murray 1964;Salvany et al 1994;Orti and Rosell 2000). In the study area, the habit of the macronodules is very fractured.…”

Plio-Quaternary extensional seismotectonics and drainage network development in the central sector of the Iberian Chain (NE Spain)

“…6). In the Calatayud area, the Miocene sediments display centripetal dips directed toward the sector where the more soluble evaporitic facies were deposited (Ortí and Rosell, 2000). This recent deformation, including anomalous tilting of the Upper Miocene carbonate sediments of Armantes and La Tronchona toward the Jalón valley (Fig.…”