**3.1 Physiography**

*Glaciers and the Polar Environment*

West longitudes, running nearly parallel to the coast line. There are some low lying, ice free areas in the coastal Antarctica such as the Schirmacher Oasis, Larsemann Hills, Vestfold Hills, Bunger Hills etc., that have been studied in detail for Late Pleistocene (~ 0.12 My) and Holocene glacial History [1–12]. These oases are distinguished from nunataks by the process of ablation. While most nunataks are located in the accumulation zone of glaciers and are kept free of ice by the strong winds, the oases are separated from the ice sheet by a distinct ablation zone. Schirmacher Oasis and Larsemann Hills, the two areas being discussed here, are such ice free regions that were covered by the ice sheet during the Last Glacial Maxima (LGM) or earlier,

*Map of Antarctica the Southern Ocean (Landsat image mosaic of Antarctica (http://lima.nasa.gov/pdf/*

*A3\_overview.pdf), with inset showing locations of Schirmacher and Larsemann Hills.*

55′E and latitudes 700

inland of the Princess Astrid coast at the northern fringe of central Dronning Maud land. Larsemann Hills on the other hand, is spread over ~50 Km <sup>2</sup>

comprise a group of ice free peninsulas (Broknes, Stornes and Brattnavet) Grovnes promontory and islands (McLeod, Fischer, Sandercock Island etc.) - located south of Prydz Bay at 69"24'S, 76′20'E on the Ingrid Christensen Coast of Princess Elizabeth Land that lie in between the Vestfold Hills and Amery Ice shelf. The two areas (Schirmacher Oasis and Larsemann Hills) are nearly 3000 km apart and experience different scale of environment, severity of climatic conditions and

The retreating ice sheet left bare rocks to be exposed to the strong Antarctic winds and other erosional processes. The areas demonstrate subdued topography with strong control of lithology and structure over the landscape. The low lying hills are devoid of horns, arêtes or conical peaks. The flat hills, dominate the

landscape. The softer rock material has weathered out giving way to the glacial melt to form scores of lakes in the depressions thus created. The freeze–thaw cycles, frost action and the salt weathering are conspicuous and have resulted in formation of conspicuous landscape typical of periglacial and glacial environment [13].

in area) is situated between

46'S, about 85 km

[12] and

44'S and 700

but are now exposed due to retreat of ice sheet. Schirmacher Oasis (approximately 35 km<sup>2</sup>

25′ E and 110

**22**

longitudes 110

**Figure 1.**

paleoclimate history.

Schirmacher Oasis and adjoining areas depict contrasting morphological units, viz. (a) the ice shelf to the north, (b) the structural hills, and (c) the continental or polar ice sheet to the south (**Figures 2**, **3** and **5**). The morphological features as seen in the ice and ice dominated regions around Schirmacher constitute an integral part of geomorphology of the region.

The ice shelf extends for about 80 km north of Schirmacher Oasis towards the Southern Ocean and displays a highly rugged and broken undulating upper surface dissected by a number of pressure ridges, crevasses and pods of melt water concentration in the western parts, as compared to a low gradient surface in the eastern sector. The Pressure ridges, formed due to the tidal activity in the sea below, and the obstacle offered by the landmass, are often seen at the contact of ice shelf and continent (**Figures 3** and **5**). A number of melt water channels concentrated close to the hills, in this part, can be noted. The continental ice sheet that encircles the Schirmacher Oasis overrides the bare rocks on its southern side. It has a regional

**Figure 2.** *Map of Schirmacher oasis showing location of Maitri (Indian Research Station) with ice shelf and continental ice.*

#### **Figure 3.**

*Geomorphological map of Schirmacher oasis.*

#### **Figure 4.**

*Distribution of fresh water lakes in Schirmacher oasis and paths of glacier movement.*

northerly gradient but locally the flow has swerved because of the nunataks and the land mass of Schirmacher which offered a resistance to its normal flow. The western component of gradient is conspicuous. A broken trail of end moraines is seen at the contact of continental ice-sheet and rocks of Schirmacher at some places in eastern margin.

The rocks of Schirmacher Oasis are aligned in ENE-WSW direction and represent middle Proterozoic sequence of quartzo-feldspathic gneiss, augen gneiss, quartzite and sillimanite garnet gneiss etc. bearing close similarity to the khondalite rocks of eastern and southern India. The rocks exposed in the form of low lying hills extend roughly for about 17 km in length and 3 km in width (at its widest in the central parts), covering an area of ~35 sq. km. The ice-free area exhibits rolling subdued topography with concordant hill tops. At both its eastern and western extremities, the hills are comparatively low lying, smoothened and capped by a thin veneer of glacier boulders. The ice-free area exhibits rolling subdued topography with concordant hill top. At both its eastern and western extremities, the hills are comparatively low lying, smoothened and capped by a thin veneer of glacier boulders The elevation varies from sea level (at the margin of westernmost lake, which has broken the apparent continuity of rocks). The central part, on the other hand, exposes hills that are comparatively higher in elevation with isolated peaks of the order of 212 m and 228 m. On an average, the height varies between 120 and 130 m above m.s.l. The southern end of the Schirmacher range is slightly elevated in comparison to the steep northerly margin. The northern margin is conspicuous by its vertical escarpment almost all along its length (**Figure 3**). The escarpment at places is more

**25**

**Figure 5.**

*and disposition of lakes defining lineaments.*

*Geomorphological Insight of Some Ice Free Areas of Eastern Antarctica*

43′ 30″S,11°

The landscape of Schirmacher Oasis is dotted by more than a hundred lakes of varying dimensions (**Figure 4**). The retreating ice cap vacated the land mass and exposed the rocks of Schirmacher Oasis, scooping out the material from weaker zones in the terrain. There were also blockages created at the mouth of glaciers due to dumping of debris carried by some glaciers. Due to these phenomenon, a number of inland lakes came into existence. Aerial survey over Schirmacher Oasis reveals a definite pattern of concentration of these lakes. Considering the morphological disposition of such lakes and their genesis, these lakes have been grouped in three different classes viz., Proglacial Lakes, Periglacial Lakes (also land locked/inland lakes) and Epishelf Lakes [14]. Proglacial and periglacial lakes dominate in number over the Epishelf lakes and together account for about 87% of the total lakes. The Proglacial Lakes, formed as a result of scouring of the rocks lying at the foot of snout tongues of glaciers, are located at the margin of continental ice sheet and run all along the southern end of Schirmacher Oasis. A NNE–SSW trending lineament cutting across all the three physiographic units viz. continental ice sheet, shelf ice and hard rock, located in the eastern part, defines a prominent fault running for nearly 8.5 km. It is seen as a well-defined crevasse zone in the former two units while in the later unit, it manifests itself in the form of shearing, tight folding, and

Schirmacher Oasis forms a part of the Wohlthat Mountains which rise to elevation 3500 m above m.s.l. leading to Polar Plateau, further south wards (**Figure 2**).

escarpment demonstrating the structural control over geomorphology.

by the concavity of the hills and vertical escarpment at these locations.

*Aerial photographic mosaic of Schirmacher displaying three physiographic units (A, B and C), Pressure Ridges* 

In the central region, the orientation and location of some inland lakes define a palaeo-channel. The path of the extinct glacier is evident from the U-shaped valley containing sporadic shallow lakes. These lakes have been carved out from structural and lithological weak zones like shears, lineaments, faults etc. (**Figure 3**). The palaeo-paths of the glaciers reconstructed using the evidences of glacial striations, moraine deposits etc., indicate a bimodal direction of the glaciers i.e., NE to ENE in the western and central parts while NNW in the eastern parts (**Figure 4**). This observation is supported by the results obtained by GPS campaign [15] that shows varying magnitude of the horizontal velocities in the range of 1.89–10.88 ma−1. There are a number of epishelf lakes that are located at the northern margin of Schirmacher Oasis which have been described as 'sea bays' (**Figure 6**) as these are connected to sea from beneath and thus respond to tidal waves as is evidenced by pressure ridges. The loci of these epishelf lakes also coincide with the sites where glacial flows must be debauching the ablation material including moraines and melt water as is evidenced

42′E). The jagged hills south of

*DOI: http://dx.doi.org/10.5772/intechopen.94445*

than 140 m as in the central part (70°

#### *Geomorphological Insight of Some Ice Free Areas of Eastern Antarctica DOI: http://dx.doi.org/10.5772/intechopen.94445*

*Glaciers and the Polar Environment*

*Geomorphological map of Schirmacher oasis.*

northerly gradient but locally the flow has swerved because of the nunataks and the land mass of Schirmacher which offered a resistance to its normal flow. The western component of gradient is conspicuous. A broken trail of end moraines is seen at the contact of continental ice-sheet and rocks of Schirmacher at some places in

The rocks of Schirmacher Oasis are aligned in ENE-WSW direction and represent middle Proterozoic sequence of quartzo-feldspathic gneiss, augen gneiss, quartzite and sillimanite garnet gneiss etc. bearing close similarity to the khondalite rocks of eastern and southern India. The rocks exposed in the form of low lying hills extend roughly for about 17 km in length and 3 km in width (at its widest in the central parts), covering an area of ~35 sq. km. The ice-free area exhibits rolling subdued topography with concordant hill tops. At both its eastern and western extremities, the hills are comparatively low lying, smoothened and capped by a thin veneer of glacier boulders. The ice-free area exhibits rolling subdued topography with concordant hill top. At both its eastern and western extremities, the hills are comparatively low lying, smoothened and capped by a thin veneer of glacier boulders The elevation varies from sea level (at the margin of westernmost lake, which has broken the apparent continuity of rocks). The central part, on the other hand, exposes hills that are comparatively higher in elevation with isolated peaks of the order of 212 m and 228 m. On an average, the height varies between 120 and 130 m above m.s.l. The southern end of the Schirmacher range is slightly elevated in comparison to the steep northerly margin. The northern margin is conspicuous by its vertical escarpment almost all along its length (**Figure 3**). The escarpment at places is more

*Distribution of fresh water lakes in Schirmacher oasis and paths of glacier movement.*

**24**

eastern margin.

**Figure 4.**

**Figure 3.**

than 140 m as in the central part (70° 43′ 30″S,11° 42′E). The jagged hills south of Schirmacher Oasis forms a part of the Wohlthat Mountains which rise to elevation 3500 m above m.s.l. leading to Polar Plateau, further south wards (**Figure 2**).

The landscape of Schirmacher Oasis is dotted by more than a hundred lakes of varying dimensions (**Figure 4**). The retreating ice cap vacated the land mass and exposed the rocks of Schirmacher Oasis, scooping out the material from weaker zones in the terrain. There were also blockages created at the mouth of glaciers due to dumping of debris carried by some glaciers. Due to these phenomenon, a number of inland lakes came into existence. Aerial survey over Schirmacher Oasis reveals a definite pattern of concentration of these lakes. Considering the morphological disposition of such lakes and their genesis, these lakes have been grouped in three different classes viz., Proglacial Lakes, Periglacial Lakes (also land locked/inland lakes) and Epishelf Lakes [14]. Proglacial and periglacial lakes dominate in number over the Epishelf lakes and together account for about 87% of the total lakes. The Proglacial Lakes, formed as a result of scouring of the rocks lying at the foot of snout tongues of glaciers, are located at the margin of continental ice sheet and run all along the southern end of Schirmacher Oasis. A NNE–SSW trending lineament cutting across all the three physiographic units viz. continental ice sheet, shelf ice and hard rock, located in the eastern part, defines a prominent fault running for nearly 8.5 km. It is seen as a well-defined crevasse zone in the former two units while in the later unit, it manifests itself in the form of shearing, tight folding, and escarpment demonstrating the structural control over geomorphology.

In the central region, the orientation and location of some inland lakes define a palaeo-channel. The path of the extinct glacier is evident from the U-shaped valley containing sporadic shallow lakes. These lakes have been carved out from structural and lithological weak zones like shears, lineaments, faults etc. (**Figure 3**). The palaeo-paths of the glaciers reconstructed using the evidences of glacial striations, moraine deposits etc., indicate a bimodal direction of the glaciers i.e., NE to ENE in the western and central parts while NNW in the eastern parts (**Figure 4**). This observation is supported by the results obtained by GPS campaign [15] that shows varying magnitude of the horizontal velocities in the range of 1.89–10.88 ma−1. There are a number of epishelf lakes that are located at the northern margin of Schirmacher Oasis which have been described as 'sea bays' (**Figure 6**) as these are connected to sea from beneath and thus respond to tidal waves as is evidenced by pressure ridges. The loci of these epishelf lakes also coincide with the sites where glacial flows must be debauching the ablation material including moraines and melt water as is evidenced by the concavity of the hills and vertical escarpment at these locations.

#### **Figure 5.**

*Aerial photographic mosaic of Schirmacher displaying three physiographic units (A, B and C), Pressure Ridges and disposition of lakes defining lineaments.*

#### **Figure 6.**

*An Epishelf lake (E13) at northern margin of Schirmacher oasis. Note the vertical escarpment at the margin of lake. Continental ice sheet is located overriding part of hill (photo courtesy: Prof. Yusuke Suganuma, NIPR, Japan, SONIC: India-Japan coring expedition).*

## **3.2 Deglaciation history**

The Antarctic ice sheet extended across the continental shelf edge, before and during the LGM. The interior surface-elevation of ice sheet did not change significantly, but there was thickening of the ice around the edge of Antarctica. The LGM ice volume accounted for ~120 m of sea level lowering. Abrupt sea level rise occurred at 19,000 calendar years ago [16] following the beginning of Termination/ deglaciation and at 14,200 (Melt water Pulse 1A, MWP1A). Detailed records of δ18O reveal that the last isotopic maximum (LIM, near 18,000 cal years BP) is younger than the LGM as defined by sea level low stand (~ 21 cal ka BP). This suggests early warming of the deep sea, and implies that the deep ocean circulation must have played a key role in the termination of the LGM. During the last glacial cycle (between 19 and 71 cal ka BP), a sizeable portion of high latitude continental shelf was occupied by ice sheets. Ice sheets on the shelf were inherently unstable, being controlled by sea level. Therefore shelf glaciations played a critical role in the dynamics of deglaciation.

The isostatic rebound, a consequential to retreat of ice sheet, has resulted in uplifting of the landmass. Though the exact component of uplift cannot be quantified due to lack of beach features, the morphological evidences such as: a) existence of comparatively higher relief of the structural hills on the northern periphery of the landmass than the central corridor, b) the steep escarpment at the northern margin, and c) the indication of a fault running all along the northern margin give credence to the statement.

The different processes of deposition and erosion under the prevailing periglacial environment have left their imprints on the morphology of Schirmacher Oasis. There was an extensive phase of erosion in operation, during and after the retreat of glacier as evidenced from the erosional features such as a) rolling topography, b) absence of sharp peaks, c) glacial striations and polishing of the rock surfaces and d) the existence of en-echelon pattern of the Roche Moutonees over a large area in the oasis. Features such as block fields, cavernous pits, etc. were formed due to extreme variation in the diurnal temperatures and strong wind erosion. The superimposition of the wind features on the glacial imprints, as seen under electron microscope imply the long period of exposure of the terrain to the weathering processes after the retreat of the ice mass. The depositional features are marked by

**27**

*Geomorphological Insight of Some Ice Free Areas of Eastern Antarctica*

The detailed description of landforms is given by [13].

Hills, believed to be vacated by ice much before LGM.

extensive moraines, terraces, erratic boulders on hill tops and lacustrine deposits.

The existing planar surfaces of the Schirmacher Oasis offer a unique landscape that indicates a pre-Holocene weathering profile. In the absence of the reliable dating, it is not possible to comment with firm conviction if the surface has been a result of Mesozoic weathering profile subsequent to fragmentation and breaking of Gondwanaland supercontinent or a Pleistocene event. However, reported ages of 53.7 ± 8.2 and 51.2 ± 9.4 ka from two sediment cores [17] obtained from the lakes of Schirmacher Oasis could be correlated with the beginning of the oxygen isotopic stage 3 (MIS 3). The surficial glacial till deposit have been dated by him at 30 to 40 cal ka BP [17]. Such an old age does give credence to the hypothesis that Schirmacher was ice free during LGM and before. This is also supported by the studies [18] from other Eastern Antarctic Oases, such as Bunger and Larsemann

Two long sediment cores collected from the L-49 have been dated at different depths. The oldest dates obtained from the basal and near basal sections at 168 to 174 cm from the top have been dated at 30,640 years and 32,655 years BP. Cold conditions prevailed in the Schirmacher Oasis from 30,640–21,685 years B.P. having a low sedimentation rate of 0.005 mm/year. Warmer conditions existed between 32,655–30,640 years B.P. with a higher sedimentation rate of 0.015 mm/year. The 14C dates of another core suggested a wet climate between 29,920–28,890 years B.P. with a sedimentation rate of 0.09 mm/year [19]. Study of clay minerals from core samples has led [20] propose that there was a gradual shift in the weathering regime

Reconstruction of the paleoclimate history from the pollen spores present in the sediment samples of Lake (L-49) by [21] shows that the region witnessed cold and dry climate during 10–9 ka B.P. followed by a long phase of warm and moist climate from 9 to 2.4 ka B.P. Subsequently from 2.4–1 ka B.P. onwards, dry and cold conditions set in the Schirmacher Oasis. However, the climate ultimately turned warm and moist beginning at 1 ka B.P. The sedimentation rate of the fluvio-glacial deposits, especially in the lakes give an indication of the varying paleoclimate. It is evident from the studies that between 8000 and 3500 years BP the climate was warm as compared to the period before and after it so as to yield fast inflow of the sediments in the lakes during this period. The interpretation is in conformity with the palyonological data [22] that infers a warm, humid and warm & humid climate between this time span, on the basis of pollen studies. These alternating phases of climate were made on the basis of dominance of grasses, cosmarium (fresh water algae) etc.

The lake history from 13 ka B.P. to the present has also been attempted by using the magnetic and geochemical properties of seven vertical sediment profiles along an east–west transect in Schirmacher Oasis [23]. Further, based on the results of AMS 14C dates [24], reports that greater parts of Schirmacher was dominated by glaciers from 13 to 12.5 ka B.P and colder conditions prevailed in the Schirmacher Oasis between 13 and 12.5 ka B.P.; ~12–11.5 ka B.P. and 9.5–5 ka B.P. However, due to the onset of warming conditions (~11.5 ka B.P.), the glaciers retreated leading to the formation of five large pro-glacial lakes which are now located on the low lying valleys of the Schirmacher Oasis. Based on the environmental magnetic properties of sediments deposited in Sandy Lake, glacial–interglacial climatic variation was reconstructed for the past 42.5 cal. ka B.P. [23]. Extremely cold periods in the Schirmacher Oasis were recorded during 40.8, 36, 34.51, 29 and, 28.02–21.45 cal. Ka B.P. Relatively warm periods were documented during 38.4–39.2 cal. ka B.P., 33.7– 29.8 cal. ka B.P. and 28.5 cal.ka B.P. The Holocene period was characterized by alternating phases of relatively warm (12.55–9.9 cal. ka B.P.and 4.21–~2 cal. ka B.P) and cold (9.21–4.21 cal. Ka B.P. and from ~2 cal. ka B.P. onwards) events. These results

and climate from strongly glacial to fluvio- glacial specially around 42 ka..

*DOI: http://dx.doi.org/10.5772/intechopen.94445*

#### *Geomorphological Insight of Some Ice Free Areas of Eastern Antarctica DOI: http://dx.doi.org/10.5772/intechopen.94445*

*Glaciers and the Polar Environment*

**3.2 Deglaciation history**

*Japan, SONIC: India-Japan coring expedition).*

**Figure 6.**

dynamics of deglaciation.

credence to the statement.

The Antarctic ice sheet extended across the continental shelf edge, before and during the LGM. The interior surface-elevation of ice sheet did not change significantly, but there was thickening of the ice around the edge of Antarctica. The LGM ice volume accounted for ~120 m of sea level lowering. Abrupt sea level rise occurred at 19,000 calendar years ago [16] following the beginning of Termination/ deglaciation and at 14,200 (Melt water Pulse 1A, MWP1A). Detailed records of δ18O reveal that the last isotopic maximum (LIM, near 18,000 cal years BP) is younger than the LGM as defined by sea level low stand (~ 21 cal ka BP). This suggests early warming of the deep sea, and implies that the deep ocean circulation must have played a key role in the termination of the LGM. During the last glacial cycle (between 19 and 71 cal ka BP), a sizeable portion of high latitude continental shelf was occupied by ice sheets. Ice sheets on the shelf were inherently unstable, being controlled by sea level. Therefore shelf glaciations played a critical role in the

*An Epishelf lake (E13) at northern margin of Schirmacher oasis. Note the vertical escarpment at the margin of lake. Continental ice sheet is located overriding part of hill (photo courtesy: Prof. Yusuke Suganuma, NIPR,* 

The isostatic rebound, a consequential to retreat of ice sheet, has resulted in uplifting of the landmass. Though the exact component of uplift cannot be quantified due to lack of beach features, the morphological evidences such as: a) existence of comparatively higher relief of the structural hills on the northern periphery of the landmass than the central corridor, b) the steep escarpment at the northern margin, and c) the indication of a fault running all along the northern margin give

The different processes of deposition and erosion under the prevailing periglacial environment have left their imprints on the morphology of Schirmacher Oasis. There was an extensive phase of erosion in operation, during and after the retreat of glacier as evidenced from the erosional features such as a) rolling topography, b) absence of sharp peaks, c) glacial striations and polishing of the rock surfaces and d) the existence of en-echelon pattern of the Roche Moutonees over a large area in the oasis. Features such as block fields, cavernous pits, etc. were formed due to extreme variation in the diurnal temperatures and strong wind erosion. The superimposition of the wind features on the glacial imprints, as seen under electron microscope imply the long period of exposure of the terrain to the weathering processes after the retreat of the ice mass. The depositional features are marked by

**26**

extensive moraines, terraces, erratic boulders on hill tops and lacustrine deposits. The detailed description of landforms is given by [13].

The existing planar surfaces of the Schirmacher Oasis offer a unique landscape that indicates a pre-Holocene weathering profile. In the absence of the reliable dating, it is not possible to comment with firm conviction if the surface has been a result of Mesozoic weathering profile subsequent to fragmentation and breaking of Gondwanaland supercontinent or a Pleistocene event. However, reported ages of 53.7 ± 8.2 and 51.2 ± 9.4 ka from two sediment cores [17] obtained from the lakes of Schirmacher Oasis could be correlated with the beginning of the oxygen isotopic stage 3 (MIS 3). The surficial glacial till deposit have been dated by him at 30 to 40 cal ka BP [17]. Such an old age does give credence to the hypothesis that Schirmacher was ice free during LGM and before. This is also supported by the studies [18] from other Eastern Antarctic Oases, such as Bunger and Larsemann Hills, believed to be vacated by ice much before LGM.

Two long sediment cores collected from the L-49 have been dated at different depths. The oldest dates obtained from the basal and near basal sections at 168 to 174 cm from the top have been dated at 30,640 years and 32,655 years BP. Cold conditions prevailed in the Schirmacher Oasis from 30,640–21,685 years B.P. having a low sedimentation rate of 0.005 mm/year. Warmer conditions existed between 32,655–30,640 years B.P. with a higher sedimentation rate of 0.015 mm/year. The 14C dates of another core suggested a wet climate between 29,920–28,890 years B.P. with a sedimentation rate of 0.09 mm/year [19]. Study of clay minerals from core samples has led [20] propose that there was a gradual shift in the weathering regime and climate from strongly glacial to fluvio- glacial specially around 42 ka..

Reconstruction of the paleoclimate history from the pollen spores present in the sediment samples of Lake (L-49) by [21] shows that the region witnessed cold and dry climate during 10–9 ka B.P. followed by a long phase of warm and moist climate from 9 to 2.4 ka B.P. Subsequently from 2.4–1 ka B.P. onwards, dry and cold conditions set in the Schirmacher Oasis. However, the climate ultimately turned warm and moist beginning at 1 ka B.P. The sedimentation rate of the fluvio-glacial deposits, especially in the lakes give an indication of the varying paleoclimate. It is evident from the studies that between 8000 and 3500 years BP the climate was warm as compared to the period before and after it so as to yield fast inflow of the sediments in the lakes during this period. The interpretation is in conformity with the palyonological data [22] that infers a warm, humid and warm & humid climate between this time span, on the basis of pollen studies. These alternating phases of climate were made on the basis of dominance of grasses, cosmarium (fresh water algae) etc.

The lake history from 13 ka B.P. to the present has also been attempted by using the magnetic and geochemical properties of seven vertical sediment profiles along an east–west transect in Schirmacher Oasis [23]. Further, based on the results of AMS 14C dates [24], reports that greater parts of Schirmacher was dominated by glaciers from 13 to 12.5 ka B.P and colder conditions prevailed in the Schirmacher Oasis between 13 and 12.5 ka B.P.; ~12–11.5 ka B.P. and 9.5–5 ka B.P. However, due to the onset of warming conditions (~11.5 ka B.P.), the glaciers retreated leading to the formation of five large pro-glacial lakes which are now located on the low lying valleys of the Schirmacher Oasis. Based on the environmental magnetic properties of sediments deposited in Sandy Lake, glacial–interglacial climatic variation was reconstructed for the past 42.5 cal. ka B.P. [23]. Extremely cold periods in the Schirmacher Oasis were recorded during 40.8, 36, 34.51, 29 and, 28.02–21.45 cal. Ka B.P. Relatively warm periods were documented during 38.4–39.2 cal. ka B.P., 33.7– 29.8 cal. ka B.P. and 28.5 cal.ka B.P. The Holocene period was characterized by alternating phases of relatively warm (12.55–9.9 cal. ka B.P.and 4.21–~2 cal. ka B.P) and cold (9.21–4.21 cal. Ka B.P. and from ~2 cal. ka B.P. onwards) events. These results

are in conformity with results of other studies, as documented above. Further, the geochemical proxies (TC%, TN%, C/N ratios, δ13C and δ 15N) along with the physical proxies (grain size: sand-silt-clay) for three different periglacial lakes viz., Long Lake, Zub Lake and Sandy Lake [1–3] spanning the glacial–interglacial variations (spanning up to 43 cal ka BP). These studies presents the evolution of lake through reconstruction of productivity patterns, source of organic matter and the hydrological processes through grain size variation complimenting the environmental magnetism records from the same lakes [5, 6]. The deglaciation history from the above observation suggest most likely that parts of Schirmacher Oasis were ice-free even during the LGM. This can be supported records of consistency in the continuity of the sedimentary sequences. However, parts of Schirmacher Oasis became ice free during the last deglaciation i.e., Termination 1. Hence, to better understand the deglaciation history of Schirmacher Oasis, the sedimentary records needs to be supplemented by further studies using novel techniques such as cosmogenic dating of rock outcrops and erratic all across Schirmacher Oasis.
