Journal of Geological Research / 2011 / Article / Tab 1

Review Article

High-Resolution Monsoon Records Since Last Glacial Maximum: A Comparison of Marine and Terrestrial Paleoarchives from South Asia

Table 1

Periodwise monsoon changes from different monsoon regions inferred from different proxies.

Time periods (yr BP) calibrated datesWestern Arabian Sea records (SWM wind records) ([10, 1620] & references therein)Southeastern Arabian Sea records (SWM precipitation records) [2128]Speleothems records from India [1, 2931]Speleothem recordsfrom Oman [3234]Bay of Bengal records [3539]Northern Arabian Sea [4046]World climatic records [17, 47, 48]

21000 to 15000Weakest SWM at Last Glacial Maximum (~21 kyr BP); weak SWM during later stages of last glacial periodHigh δ 18O value of Gs. ruber, low productivity, that is, low Corg  and high Pteropods abundance suggests low runoff into eastern Arabian Sea indicating reduced monsoon.No record availableWeak SW monsoon, suggested by high δ 18O of Gs. sacculifer and Gs. ruber and minimum fluvial discharge observed by the high Chlorite/Illite ratio, low Kaolinite abundance.Weak SWM based on low TOC values with minimum at ~16 kyr BP matching with Heinrich event 1.Part of last glacial period, Synchronous with Greenland aridity
15000 to 11700SWM strengthening commences; weaker monsoon during colder episodes such as Younger DryasSWM precipitation starts increasing with weaker/stronger monsoon during cooler/warmer episodesδ 18O in speleothem from Timta cave, western Himalaya show fluctuating monsoon with lesser precipitation during cooler periodsNo Speleothem record availableIncreasingly stronger SWM suggested by low δ 18O of foraminifer; weaker/stronger monsoon during cooler/warmer episodesFluctuating monsoon inferred; weaker monsoon during cooler periods such as Younger DryasDeglaciation period, Synchronous with European Bolling-Allerod warm event, also coeval with melt water Pulse IA.
11700 to 10200SW monsoon still weak as deciphered from multiple proxiesHigh δ 18O value of Gs. ruber, low Corg  and high Pteropods abundance suggest low runoffNo Speleothem record availableδ 18O of Gs. sacculifer and Gs. ruber reduced fluvial fluxsuggested by the high C/I ratio, low Kaolinite abundance suggested the Weak SWMIncreasing monsoon observed during this period; early Holocene Monsoon maxima observed; δ 18O record don’t show a clear-cut early Holocene monsoon maximaEnd of Younger Dryas & beginning of Holocene
10200 to 9800Multiple proxiessuggest strong SWM early Holocene monsoon maximaδ 18O value foraminifera do not show a clear-cut early Holocene monsoon maxima but suggest a slightly increasing trend during that periodLow δ 18O value of the speleothem suggests high rainfallδ 18O value of warm mixed dweller planktic foraminifera do not show a clear-cut early Holocene monsoon maxima but suggest a slightly increasing trend during that period similar to Eastern AS recordsEarly Holocene monsoon maxima matches with warm north Atlantic climate (low haematite in sediment cores)

9800–8800SWM weakened after early Holocene monsoon maximaδ 18O value of Gs. ruber suggest low runoffNo Speleothem record availablePositive excursion in the value of δ 18O of stalagmite suggests arid climateDecreasing trend in the value of δ 18O of Gs. sacculifer and Gs. ruber suggest higher runoffFrom early to mid-Holocene, the Total Organic Carbon values in the core 111KL stays more or less uniform indicating unvarying monsoon, while the δ 18O from nearby cores either stay unvarying or display a negative excursion indicating strengthening monsoonVery high percentage of hematite from N. Atlantic suggests cool period
8800–5400Up to mid-Holocene, SWM was strong based on multiple proxies although % Gs. bulloides exhibit a declining trendlow δ 18O value of Gr. menardii reported and suggesting high rainfallNo Speleothem record availableIncreasing value of δ 18O of stalagmite suggest increasingly arid climate at the Oman SiteMaximum fluvial discharge suggested by low δ 18O and strong SW monsoon.Low percentage of hematite from N. Atlantic suggests warm period; temperature reconstruction from Greenland Ice cores (GISP2) suggest warm climate; 8.2 kyr cool event from GISP2 is not reflected in monsoon reduction

5400–2900During Mid-Holocene to early part of late Holocene, multiple studies show slightly increasing monsoon but a few also observed a decline (e.g., % Gs. bulloides)High rain fall suggested by the lower value of δ 18O Gs. sacculifer and Gs. ruber No Speleothem record availablefrom IndiaIncreasing trend in δ 18O value was observed in the Oman stalagmite suggesting decreasing SWMHigh water discharged by G-B river suggested by lower values of δ 18O Gs. ruber. More negative values of δ 18O of Gs. sacculifer and Gs. ruber suggest the higher runoffAfter mid-Holocene, the TOC values decreases of Gs. ruber indicating declining monsoon while proxies like δ 18O, Ba/Al suggest an unvarying or strengthening monsoonLow percentage of hematite at N. Atlantic suggests the humid, warm climate; GISP2 suggests continuous, unvarying warmth

2900–2100Declining SWM deciphered from several studiesPositive δ 18O values of Gs. ruber suggest low runoff.High-resolution speleothem records available from India; declining SWM suggested by increasingly positive δ 18O of Gupteswar and Sota speleothem recordsNo growth of Oman StalagmiteHigh Chlorite content and δ 18O higher value suggest the arid climateHigh runoff from Indus river suggested by thicker varve sediment layerGISP2 temperature records suggest unvarying northern hemisphere, high-latitude warmth

2100–1900A period of widespread aridity is reported from varied regions & proxies such as δ 18O of foraminifera, abundance (~5%) of Globigerina bulloides and reduction in dinoflagellate population in the west Arabian sea suggesting weak upwelling, weak SWMPositive δ 18O values of foraminifera suggest low freshwater run-off indicating severely weakened SWM precipitation.Extremely low rain fall recorded from Gupteswar stalactite, suggested by the prominent positive excursion in δ 18O valuesNo growth of Oman StalagmiteLow Chlorite ratio, high Kaolinite ratio and depletion in δ 18O of Gs. ruber suggests the arid climate andreduced water discharge in to BOBPositive values of δ 18O & reduced varve thickness indicate reduced Indus river dischargeLow percentage of hematite at N. Atlantic suggests humid, warm climate

1900–1600Slightly strengthening monsoon but overall the monsoon is on weaker sideδ 18O records of Gs. ruber and Gs. sacculifer suggest increasing SWMLower δ 18O record from both Gupteswar & Sota caves suggest increasing trend of rainfall.No growth of Oman StalagmiteSlight positive excursion observed in the foraminiferal δ 18O values indicating declining monsoonAn increase in the thickness of varve sediment suggests the higher water discharge from IndusHigher hematite content suggest cold climate in N. Atlantic

1500–1400Very low abundance of Globigerina bulloides (5%) suggests extreme reduction in upwelling and wind strengthHigher value of δ 18O records of Gs. ruber and Gs. sacculifer suggest weakening of SWMHigh δ 18O of Gupteswar stalactite, Orissa suggests the weak monsoonal run-offNo growth of Oman StalagmiteSlightly declining trend in δ 18O values of foraminifera indicate strengthening monsoonAn increase in the thickness of varved sediments suggests higher water discharge from IndusLow value of Hematite percentage at North Atlantic (Medieval warm period)
1400–1200Multiple proxies suggest increasing monsoon during this periodA clear-cut decreasing trend in foraminiferal δ 18O values indicate strengthening monsoonDepletion in δ 18O shows increasing trend of rainfall recorded at Gupteswar and Dandak caves.High precipitation indicated by Oman stalagmite depleted δ 18O record

1200–1000Low Gg. bulloides abundance & other proxies suggest significantly weak upwelling due to weakened SWMAn arid event centered at ~1100 yr BP reflected by the sudden decline in δ 18O of Gs. ruber and Gs. sacculifer Low rain fall recorded at Gupteswar and Dandak cavesHigher δ 18O values suggest arid conditions









After a slight peak, the δ 18O exhibit positive excursion indicating reduced SWM strength
Lower varve thickness and high δ 18O of Gs. ruber suggests weak SWM (63 KA)Low value of Hematite percentage at North Atlantic (Medieval warm period)
1000–800Very low abundance of Globigerina bulloides suggests the weak SWMIncrease in δ 18O records Gs. ruber and Gs. sacculifer of due to increase in salinity of east Arabian Sea suggests major event of aridity centered at ~850 yr BPAridity observed at Dandak caves indication reduced precipitationOman stalagmite records the increase in δ 18O which suggest an arid conditionLower Varve thickness and sharp increase in δ 18O of Gs. ruber suggests the weak SWM
800–500Decreasing trend of Gg. bulloides abundance suggests weak SWMLow runoff, reduced precipitation event centered at ~500 yr BP suggested by increase in δ 18O of Gs. ruber and Gs. sacculifer Depletion in δ 18O shows increasing trend of rainfall recorded in Gupteswar & Dandak speleothemNegative excursion in speleothem δ 18O values indicate strengthened precipitationLower varve thickness suggests weak monsoon strengthIncreasing trend in the % of hematite at N.Atlantic suggests the cool climate
500–400High abundance of Gg. bulloides suggests strong SWMIncrease in the δ 18O records of Gs. ruber and Gs. sacculifer suggest weak SWMReduced precipitation suggested by increase in δ 18O speleothems recordReduced precipitation suggested by increase in δ 18O record in Oman stalagmiteLower Varve thickness and high δ 18O of Gs. ruber suggests weak SWMSynchronous with little Ice Age, cooling at Bermuda rise and brief increase in hematite percentage
400–300Very low abundance of Globigerina bulloides suggests weak SWM




SWM shows an increasing trend
High rain fall inferred from Dandak, and Gupteswar caves




No growth of Oman Stalagmite
Ganges-Brahmaputra river discharge shows a declining trend



High varve thickness off Karachi and low δ 18O of Gs. ruber suggest strong SWM
300–100High abundance of Gg. bulloides suggests the strong SWMRain fall increased as seen in from Dandak Gupteswar Sota and Akalagavi caves, the lower δ 18O record suggests higher runoffLow value of Hematite percentage at North Atlantic indicating warm, humid climate
50–PresentHigh abundance of Gg. bulloides suggest strong SWMVery low rain fall was recorded from Dandak and Akalagavi caves

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