A Multi-Archive Reconstruction of Holocene Summer and Winter Monsoon Variability in NW South Asia

This thesis investigates the paleoclimate of the Indus River Basin and surrounding areas of northwest (NW) South Asia over the last 12,000 years, covering a critical period of human history. The region’s climate is characterized by two overlapping rainfall systems: the Indian Summer Monsoon (ISM) and the Indian Winter Monsoon (IWM). A shift in these monsoon systems has been documented throughout South Asia at 4.2 ka BP, with potential effects on the development and decline of the Indus Civilization (c. 5- 3.6 ka BP). This thesis examines the connection between climate and cultural shifts by providing new records from three climate archives spanning 1500 km from the Arabian Sea to the Thar Desert and Himalayan Mountains. The chapters feature δ¹⁸O and δ¹³C of three foraminifer species in marine core 63KA over 8.8-7.6 ka BP and 5.4-3.0 ka BP, gypsum from three Holocene Thar Desert playa lakes, and sub-annually resolved trace element and stable isotope data from DHAR-1 speleothem covering 4.2-2.5 ka BP. The major findings from this thesis contribute to a more comprehensive understanding of climate change in NW South Asia throughout the Holocene. The three Thar Desert playa lakes began accumulating gypsum c. 11 ka BP, aligning with a post- glacial strengthening ISM. Prismatic gypsum crystals and uniformly high δ¹⁸O of gypsum hydration water from early-mid Holocene deposits suggest relatively deep lake levels during this phase. Similarly, the δ¹⁸O of marine core 63KA foraminifer species dwelling in surface and thermocline layers demonstrate a stronger ISM over 8.8-7.6 ka BP and a strengthening IWM from 8.8-8.6 ka BP. By 4.8 ka BP, the ISM started weakening, but IWM strength peaks from 4.5-4.3 ka BP. A wet period c. 5-4.4 ka BP is also apparent from high δ¹⁸O of gypsum hydration water at Karsandi playa. The late Holocene droughts after 4.2 ka BP are well-documented by the precise (age error ± 18 years) DHAR-1 reconstruction, which tracks ISM strength via δ¹⁸O and winter aridity using δ¹³C, Sr²⁺ U²⁺, and Ba²⁺. Weakened ISM and IWM both contributed to the 230-year drought period with three distinct arid phases (4.2-4.17 ka BP, 4.14-4.08 ka BP, and 4.06-3.97 ka BP). Core 63KA shows minimum Indus River discharge and weakened IWM over the same interval, whereas Lunkaransar playa shows a protracted lake level decline, and aeolian sand replaces gypsum deposition at Karsandi by 3.2 ka BP. Shallow playa systems briefly recover at Lunkaransar and Khajuwala during the late Holocene, but Khajuwala eventually desiccates permanently.Tworains ERC grant 648609 WIHM ERC grant 339694 QUEST H2020 Marie Skodowska-Curie actions 69103

Reconstructing Holocene landscape and environmental changes at Lago Rogaguado, Bolivian Amazon

Funder: University of CambridgeAbstractWe performed geochemical analyses of two lake sediment cores (1.25 and 1.5 m long) from Lago Rogaguado, which is a large (315 km2) and shallow lake in the Llanos de Moxos, Bolivian Amazon, to investigate Holocene environmental changes based on a multi-proxy dataset (XRF, density, grain size, C:N, and macrocharcoal). One of the two cores provides a history of environmental changes in the Llanos de Moxos from 8100 cal BP until present, which supplements previously published pollen and microscopic charcoal records. Our analyses indicate lake expansion at 5800 cal BP, which may relate to tectonic activity. This was followed by further increasing lake levels, peaking at approximately 1050–400 cal BP, which supports increasingly wetter conditions in the Llanos de Moxos after the mid-Holocene. A fourfold increase in macroscopic charcoal accumulation rate and a more than fivefold increase in sedimentation rates supports anthropogenic fire activity at around 1450 cal BP (500 CE), suggesting that pre-Columbian populations used fire to actively manage the landscape during a period of maximum lake levels around Lago Rogaguado. From 400–100 cal BP, higher C:N, larger grain sizes and peaks in macroscopic charcoal accumulation rates suggest increased watershed erosion associated with increased biomass burning, possibly related to intensified land use.</jats:p

Indian winter and summer monsoon strength over the 4.2 ka BP event in foraminifer isotope records from the Indus River delta in the Arabian Sea

Abstract. The plains of northwest South Asia receive rainfall during both the Indian summer (June–September) and winter (December–March) monsoon. Researchers have long attempted to deconstruct the influence of these precipitation regimes in paleoclimate records, in order to better understand regional climatic drivers and their potential impact on human populations. The mid–late Holocene transition between 5.3 and 3.3 ka is of particular interest in this region because it spans the period of the Indus Civilization from its early development, through its urbanization, and onto eventual transformation into a rural society. An oxygen isotope record of the surface-dwelling planktonic foraminifer Globigerinoides ruber from the northeast Arabian Sea provided evidence for an abrupt decrease in rainfall and reduction in Indus River discharge at 4.2 ka, which the authors linked to the decline in the urban phase of the Indus Civilization (Staubwasser et al., 2003). Given the importance of this study, we used the same core (63KA) to measure the oxygen isotope profiles of two other foraminifer species at decadal resolution over the interval from 5.4 to 3.0 ka and to replicate a larger size fraction of G. ruber than measured previously. By selecting both thermocline-dwelling (Neogloboquadrina dutertrei) and shallow-dwelling (Globigerinoides sacculifer) species, we provide enhanced detail of the climatic changes that occurred over this crucial time interval. We found evidence for a period of increased surface water mixing, which we suggest was related to a strengthened winter monsoon with a peak intensity over 200 years from 4.5 to 4.3 ka. The time of greatest change occurred at 4.1 ka when both the summer and winter monsoon weakened, resulting in a reduction in rainfall in the Indus region. The earliest phase of the urban Mature Harappan period coincided with the period of inferred stronger winter monsoon between 4.5 and 4.3 ka, whereas the end of the urbanized phase occurred some time after the decrease in both the summer and winter monsoon strength by 4.1 ka. Our findings provide evidence that the initial growth of large Indus urban centers coincided with increased winter rainfall, whereas the contraction of urbanism and change in subsistence strategies followed a reduction in rainfall of both seasons. ER

Indian winter and summer monsoon strength over the 4.2 ka BP event in foraminifer isotope records from the Indus River delta in the Arabian Sea

The plains of northwest South Asia receive rainfall during both the Indian summer (June–September) and winter (December–March) monsoon. Researchers have long attempted to deconstruct the influence of these precipitation regimes in paleoclimate records, in order to better understand regional climatic drivers and their potential impact on human populations. The mid–late Holocene transition between 5.3 and 3.3 ka is of particular interest in this region because it spans the period of the Indus Civilization from its early development, through its urbanization, and onto eventual transformation into a rural society. An oxygen isotope record of the surface-dwelling planktonic foraminifer Globigerinoides ruber from the northeast Arabian Sea provided evidence for an abrupt decrease in rainfall and reduction in Indus River discharge at 4.2 ka, which the authors linked to the decline in the urban phase of the Indus Civilization (Staubwasser et al., 2003). Given the importance of this study, we used the same core (63KA) to measure the oxygen isotope profiles of two other foraminifer species at decadal resolution over the interval from 5.4 to 3.0 ka and to replicate a larger size fraction of G. ruber than measured previously. By selecting both thermocline-dwelling (Neogloboquadrina dutertrei) and shallow-dwelling (Globigerinoides sacculifer) species, we provide enhanced detail of the climatic changes that occurred over this crucial time interval. We found evidence for a period of increased surface water mixing, which we suggest was related to a strengthened winter monsoon with a peak intensity over 200 years from 4.5 to 4.3 ka. The time of greatest change occurred at 4.1 ka when both the summer and winter monsoon weakened, resulting in a reduction in rainfall in the Indus region. The earliest phase of the urban Mature Harappan period coincided with the period of inferred stronger winter monsoon between 4.5 and 4.3 ka, whereas the end of the urbanized phase occurred some time after the decrease in both the summer and winter monsoon strength by 4.1 ka. Our findings provide evidence that the initial growth of large Indus urban centers coincided with increased winter rainfall, whereas the contraction of urbanism and change in subsistence strategies followed a reduction in rainfall of both seasons

A NOVEL APPROACH TO UNDERSTANDING MICROWAVE HEATING OF ZIRCONIA

ABSTRACT Savings in processing time (up to 90%) and energy (20-80%) are expected in microwave sintering of ceramics, as this technology breaks through into industrial firing processes. Linn High Therm had developed a high temperature hybrid microwave system in anticipation of industries needs. Typically, silicon carbide susceptors are used to initiate heating from room temperature, where many ceramics have low dielectric losses. The loss increases with temperature, and at some &quot;kick in&quot; transition temperature, the ceramic load heats preferentially over the susceptors. In this work the effect of dopant type and crystal structure of zirconia on the &quot;kick in&quot; temperature was observed using silicon carbide susceptors

Author Correction: Intensified summer monsoon and the urbanization of Indus Civilization in northwest India.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.NERC (NE/H011463/1

Intensified summer monsoon and the urbanization of Indus Civilization in northwest India

Today the desert margins of northwest India are dry and unable to support large populations, but were densely occupied by the populations of the Indus Civilization during the middle to late Holocene. The hydroclimatic conditions under which Indus urbanization took place, which was marked by a period of expanded settlement into the Thar Desert margins, remains poorly understood. We measured the isotopic values (δ18O and δD) of gypsum hydration water in paleolake Karsandi sediments in northern Rajasthan to infer past changes in lake hydrology, which is sensitive to changing amounts of precipitation and evaporation. Our record reveals that relatively wet conditions prevailed at the northern edge of Rajasthan from ~5.1 ± 0.2 ka BP, during the beginning of the agricultural-based Early Harappan phase of the Indus Civilization. Monsoon rainfall intensified further between 5.0 and 4.4 ka BP, during the period when Indus urban centres developed in the western Thar Desert margin and on the plains of Haryana to its north. Drier conditions set in sometime after 4.4 ka BP, and by ~3.9 ka BP an eastward shift of populations had occurred. Our findings provide evidence that climate change was associated with both the expansion and contraction of Indus urbanism along the desert margin in northwest India

Permeability Prediction in Tight Carbonate Rocks using Capillary Pressure Measurements

The prediction of permeability in tight carbonate reservoirs presents ever more of a challenge in the hydrocarbon industry today. It is the aim of this paper to ascertain which models have the capacity to predict permeability reliably in tight carbonates, and to develop a new one, if required. This paper presents (i) the results of laboratory Klinkenberg-corrected pulse decay measurements of carbonates with permeabilities in the range 65 nD to 0.7 mD, (ii) use of the data to assess the performance of 16 permeability prediction models, (iii) the development of an improved prediction model for tight carbonate rocks, and (iv) its validation using an independent data set. Initial measurements including porosity, permeability and mercury injection capillary pressure measurements (MICP) were carried out on a suite of samples of Kometan limestone from the Kurdistan region of Iraq. The prediction performance of sixteen different percolation-type and Poiseuille-type permeability prediction models were analysed with the measured data. Analysis of the eight best models is included in this paper and the analysis of the remainder is provided in supplementary material. Some of the models were developed especially for tight gas sands, while many were not. Critically, none were developed for tight gas carbonates. Predictably then, the best prediction was obtained from the generic model and the RGPZ models (R2 = 0.923, 0.920 and 0.915, respectively), with other models performing extremely badly. In an attempt to provide a better model for use with tight carbonates, we have developed a new model based on the RGPZ theoretical model by adding an empirical scaling parameter to account for the relationship between grain size and pore throat size in carbonates. The generic model, the 28 new RGPZ Carbonate model and the two original RGPZ models have been tested against independent data from a suite of 42 samples of tight Solnhofen carbonates. All four models performed very creditably with the generic and the new RGPZ Carbonate models performing well (R2 = 0.840 and 0.799, respectively). It is clear from this study that the blind application of conventional permeability prediction techniques to carbonates, and particularly to tight carbonates, will lead to gross errors and that the development of new methods that are specific to tight carbonates is unavoidable

Living in the hinterland: Survey and excavations at Lohari Ragho 2015–2017

Living in the hinterland: Survey and excavations at Lohari Ragho 2015–201

Permeability in Rotliegend gas sandstones to gas and brine as predicted from NMR, mercury injection and image analysis

Permeability characterisation of low permeability, clay-rich gas sandstones is part of production forecasting and reservoir management. The physically based Kozeny (1927) equation linking permeability with porosity and pore size is derived for a porous medium with a homogeneous pore size, whereas the pore sizes in tight sandstones can range from nm to μm. Nuclear magnetic resonance (NMR) transverse relaxation was used to estimate a pore size distribution for 63 samples of Rotliegend sandstone. The surface relaxation parameter required to relate NMR to pore size is estimated by combination of NMR and mercury injection data. To estimate which pores control permeability to gas, gas permeability was calculated for each pore size increment by using the Kozeny equation. Permeability to brine is modelled by assuming a bound water layer on the mineral pore interface. The measured brine permeabilities are lower than predicted based on bound water alone for these illite rich samples. Based on the fibrous textures of illite as visible in electron microscopy we speculate that these may contribute to a lower brine permeability