Chemie der Erde 68 (2008) 313–322 Geochemical zones and reconstruction of late Holocene environments from shallow core sediments of the Pachapadra paleo-lake, Thar Desert, India P.D. Roy a,b,Ã , W. Smykatz-Kloss a , O. Morton c a Institute of Mineralogy and Geochemistry, University of Karlsruhe, 76131 Karlsruhe, Germany b Centro de Investigaciones en Ciencias de la Tierra, Universidad Auto´noma del Estado de Hidalgo, carr-Pachuca-Tulancingo, Km. 4.5, 42184 Pachuca, Me´xico c Instituto de Geofı´sica, Universidad Nacional Auto´noma de Me´xico, Cuidad Universitaria, 04510 Me´xico, DF Received 11 November 2005; accepted 11 January 2006 Abstract Lithostratigraphy, mineralogy, major and trace element concentrations, carbon and sulphur contents are investigated from a shallow depth profile from Pachapadra paleo-lake, Thar Desert, north-western India, to understand the phases of paleo-hydrology and paleo-limnology. Based on the geochemical proxies (Na/Al, Si/Al, Zr/ Al and Ca/Mg) and evaporite mineralogy, the depth profile is divided into three geochemical zones of variable sediment–water interaction, evaporation and aeolian activity. The sub-recent zone (I) enriched in halite (NaCl) indicates low chemical weathering and higher aeolian input. The intermediate relatively humid zone II is enriched in major elements, trace elements and calcite (CaCO 3 ) and reflects higher chemical weathering in the catchments. Zone III is enriched in gypsum (CaSO 4  2H 2 O) and characterised by lower chemical weathering, higher aeolian activity and evaporation. r 2006 Elsevier GmbH. All rights reserved. Keywords: Evaporite mineralogy; Paleo-hydrology; Holocene; Geochemical zones; Paleo-lake; Thar Desert; India 1. Introduction Deserts all over the world have formed as a result of changes in atmospheric circulation pattern and, hence, distribution of rainfall (Dawson, 1992). These are the regions which witness the interplay of climate on geology with minimum interference from biology. So the geological and stratigraphical records from different archives, e.g., lacustrine, fluvial and aeolian, from the desert margins or arid–semi-arid climatic transitions are pristine and are studied to understand the paleo- hydrology, paleo-climatology and, hence, changes in past atmospheric circulation pattern. The geographical location of the Thar Desert in a transitional monsoon regime that is typical of general mid-latitudinal atmospheric circulation implies that minor perturbation in this pattern affects the hydrology and influences the geomorphology of the region in an amplified scale. A very systematic spatial climatic shift in the entire region has been documented by the deposits of loess and fossil sand dunes (Wasson et al., 1983; Dhir et al., 1992; Tripathi and Rajamani, 1999) in the ARTICLE IN PRESS www.elsevier.de/chemer 0009-2819/$ - see front matter r 2006 Elsevier GmbH. All rights reserved. doi:10.1016/j.chemer.2006.01.006 Ã Corresponding author. Centro de Investigaciones en Ciencias de la Tierra, Universidad Auto´noma del Estado de Hidalgo, carr-Pachuca- Tulancingo, Km. 4.5, 42184, Pachuca, Me´xico. Tel.: +52 017717172000x6621/6622. E-mail address: priyadarsi@lycos.com (P.D. Roy).