Holocene calcrete crust deposits on the moraine of Batura Glacier, northern Pakistan

Abstract

Calcretes can be observed on the surface of old moraines around Batura Glacier in the upper Hunza Valley, Karakoram Mountains, Pakistan. They develop as a calcareous crust cementing small gravels under boulders. In order to understand the genesis of the calcrete crust, a variety of methods were employed: (i) study of mineralogy and geochemistry of a calcrete crust precipitated on the lateral moraine using X-ray diffractometer and electron probe microanalysis; (ii) analysis of solute chemistry of surface water and ice bodies around the Batura Glacier; and (iii) accelerator mass spectrometry 14 C dating of the crust itself. The results indicate that the calcrete crust has definite laminated layers composed of a fine-grain and compact calcite layer, and a mineral fragment layer. The chemical composition of the calcite layer is approximately 60% CaO and 1% MgO. The mineral fragment layer consists of rounded grain materials up to 0.2 mm in diameter. It shows a graded bedding structure with fine grains of quartz, albite and muscovite. Meanwhile, as the Paleozoic Pasu limestone is distributed around the terminal of Batura Glacier, Ca cations dissolve in the melt water of the glacier. Accordingly, the calcrete crust is precipitated by decreases in CO 2 partial pressure from glacier ice and evaporation of the melt water, including high concentration of Ca 2+ at ephemeral streams and small ponds stagnating between the moraine and glacial ice. On the basis of the AMS 14 C age, the calcrete is considered to have formed approximately 8200 calibrated years BP under the Batura glacial stage.

Palaeo-environmental significance of evaporative calcite crusts in the Untersee Oasis, East Antarctica

“…Clark et al 2004, Lacelle 2007; alternatively, if they precipitated from waters in equilibrium with atmospheric CO 2 , they can be used as palaeo-environmental proxies. For example, the 14 C ages of carbonate crusts on the surface of moraines were used to infer the timing of deglaciation in east-central Ellesmere Island (high Arctic Canada; Blake 2005), southern Baffin Island (low Arctic Canada; Lacelle et al 2007) and northern Pakistan (Waragai 2005), and the chronologies matched well with those derived from other methods.…”

Calcrete profiles in Puthukulam quarry section, Sathankulam region, Southern Tamilnadu, India: implications on palaeoclimate significance

“…The clay minerals and other minerals are identified through 'd' spacing values and their relative intensities. Qualitative mineralogy of clay minerals and other minerals of calcrete samples through XRD analysis was determined with the standard procedure (Sachinath Mitra, 1989;Kile and Eberl, 2000;Harris et al, 2008;Jiménez-Espinosa and Jiménez-Millán, 2003;Waragai, 2005;Hong et al, 2007;Moazallahi and Farpoor, 2012;Udayanapillai et al, 2015).…”