Waseem Raza

Stalagmite Inferred High Resolution Climatic Changes throughPleistocene-Holocene Transition in Northwest Indian Himalaya

Investigated for d18O and d13C isotopes, mineralogy and growth rate, a 20 cm long and 230Th-dated calcite stalagmite from Kalakot (Jammu and Kashmir Himalaya), has recorded high resolution precipitation variability during the Pleistocene-Holocene transition. At present, the study area is influenced by both the Indian Summer Monsoon (ISM) and Westerlies. The StalAge model indicates that the stalagmite grew between 16.3 ka to 9.5 ka BP under the ideal isotopic equilibrium conditions as revealed by the Hendy test results. The d18O and d13C values range from -5.41 to -8.82% and -7.09 to -10.84% respectively. Although the U/Th chronology is poor due to low Uranium content in the samples resulting in relatively large errors, the first stalagmite inferred precipitation variability reconstructed from NW Indian Himalaya makes this study significant. The near footprints of three global events, e.g., Older Dryas (OD), Allerod period and Younger Drays (YD) can be noticed at ~14.3-13.9, 13.9-12.7 and 12.7-12.2 ka BP. The precipitation strength was weaker during the OD and YD, but was stronger during the Allerod interstadial. By the termination of YD interval, the climate seems fluctuating in the NW Himalaya. There seems variation in commencement, duration and termination of the above mentioned events in different parts of the globe due to latitude location and response time.

Reconstruction of Indian monsoon precipitation variability between 4.0 and 1.6 ka BP using speleothem δ 18 O records from the Central Lesser Himalaya, India

The present study documents the monsoon precipitation variability spanned ~xa02500xa0years, between 4.0 and 1.6xa0ka BP (before 1950 AD), from the Central Lesser Himalaya, India, using δ18O measurements of Tityana cave stalagmite (hereafter referred as TC1). At present, the cave receives precipitation from both Indian Summer Monsoon (ISM) and Western Disturbances (WDs). The δ18O variation between −xa08.04 and −xa010.46‰ through growth axis of the TC1 and five 14C AMS dates (due to large age uncertainty by 230Th/U method) have allowed us to identify the mid to late Holocene multi-decadal to centennial scale climatic oscillations. The higher δ18O values indicate the weakening of the monsoon precipitation, while the lighter values represent the stronger monsoon precipitation strength. Based on the fluctuations in δ18O values, three distinct phases of the precipitation variability are distinguished as, declined/decreased precipitation between ~xa04.0 and 3.4xa0ka BP with peak aridity around ~xa03.4xa0ka BP, followed by slightly improved conditions from ~xa03.4 to ~xa02.7xa0ka BP. Subsequently, the climate was reduced from ~xa02.7xa0ka BP onwards until the end of stalagmite growth, around ~xa01.6xa0ka BP with spikes of two major drought events centred at ~xa01.9 and ~xa01.6xa0ka BP. In general, the droughts, centred at ~xa03.4, ~xa01.9 and ~xa01.6xa0ka BP, are characterized by abrupt drop (from −xa08.12 to −xa08.04‰) in the δ18O values and point to the weakening of the monsoon. One of the major drought events at ~xa03.4xa0ka BP can be correlated with the collapse of the Indus valley civilization in the NW India. A close correspondence of the TC1 data set with other WDs influenced regimes likely indicates a relative impact of mid-latitude WDs after transition of the mid-late Holocene around 3.5–3.4xa0ka BP.