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Supporting Data for: A high-Arctic inner shelf–fjord system from the Last Glacial Maximum to the Present: Bessel Fjord and SW Dove Bugt, NE Greenland
No full textData sets which support the manuscript "A high-Arctic inner shelf–fjord system from the Last Glacial Maximum to the Present: Bessel Fjord and SW Dove Bugt, NE Greenland". This includes bathymetry data as well as Multi Sensor Core Logger data obtained from three gravity cores. This data was originally collected in Dove Bugt and Bessel Fjord in Northeast Greenland during a 2017 TUNU cruise aboard the RV Helmer Hanssen. Abstract: The Greenland Ice Sheet (GrIS) responds rapidly to the present climate, therefore, its response to the predicted future warming is of concern. To learn more about the impact of future climatic warming on the ice sheet, decoding its behavior during past periods of warmer than present climate is important. However, due to the scarcity of marine studies reconstructing ice sheet conditions on the Northeast Greenland shelf and adjacent fjords, the timing of the deglaciation over marine regions and its connection to forcing factors remain poorly constrained. This includes data collected in fjords that encompass the Holocene Thermal Maximum (HTM), a period in which the climate was warmer than it is at present. This paper aims to use new bathymetric data and the analysis of sediment gravity cores to enhance our understanding of ice dynamics of the GrIS in a fjord and inner shelf environment as well as give insight into the timing of deglaciation and provide a palaeoenvironmental reconstruction of southwestern Dove Bugt and Bessel Fjord since the Last Glacial Maximum (LGM). North-south oriented glacial lineations, and the absence of pronounced moraines in southwest Dove Bugt, an inner continental shelf embayment (trough), suggests the southwards and offshore flow of Storstrømmen, the southern branch of the Northeast Greenland Ice Stream (NEGIS). Sedimentological data suggests that an ice body, theorized to be the NEGIS, may have retreated from the region slightly before ~11.4 cal. ka BP. The seabed morphology of Bessel Fjord, a fjord terminating in southern Dove Bugt, includes numerous basins, separated by thresholds. The position of basin thresholds, which include some recessional moraines, suggest that the GrIS had undergone multiple halts or readvances during deglaciation, likely during one of the cold events identified in the Greenland Summit temperature records. A minimum age of 7.1 cal. ka BP is proposed for the retreat of ice through the fjord to or west of its present-day position in the Bessel Fjord catchment area. This suggests that the GrIS retreated from the marine realm in early Holocene, around the onset of the HTM in this region, a period when the mean July temperature was at least 2-3 oC higher than at present and remained at or west of this onshore position for the remainder of the Holocene. The transition from predominantly mud to muddy sand layers in a mid-fjord core at ~4 cal. ka BP may be the result of increased sediment input from nearby and growing ice caps. This shift may suggest that in the Late Holocene (Meghalayan), a period characterized by a temperature drop to modern values, ice caps in Bessel Fjord probably fluctuated with greater sensitivity to climatic conditions than the NE sector of the GrIS.<p
Dannelse og utvikling av submarine kanjoner på kontinentalskråningen utenfor Lofoten
Full text linkTre kanjoner på kontinentalskråningen utenfor Lofoten er studert ut fra multistråle
batymetridata, høyoppløselig seismiske data og foto av havbunnssedimenter. Formålet med
denne studien er å diskutere dannelse, utviklingen av og den yngste aktiviteten i de tre
kanjonene.
To hovedhypoteser vedrørende kanjoners dannelse råder i dag; dannelse fra bunn av
kontinentalskråningen og oppover eller fra toppen av skråningen og nedover. Dannelsen og
utviklingen av de tre kanjonene er diskutert med utgangspunkt i disse to hypotesene. To av
kanjonene starter på øvre del av kontinentalskråningen, har en bred pæreformet øvre del og en
smalere, rett nedre del. Basert på dataene tilgjengelig i dette studiet har det ikke vært mulig å
favorisere en av de to hypotesene for dannelsen av disse to kanjonene. Den tredje kanjonen
strekker seg fra eggakanten og ned til dyphavssletten og er U-formet i tverrsnitt. Denne
kanjonen ligger i forlengelsen av et glasialt erodert trau på kontinentalhylla. Kanjonen antas å
ha utviklet seg ved en kombinasjon av «bunn opp»- og «topp ned» teoriene.
Amfiteaterformede skrenter langs veggene og i bunn av alle kanjonene tyder på at
utglidninger har vært en viktig faktor for kanjonenes utvikling. En mulig utviklingsmodell og
alder for de tre kanjonene er forslått, og dannelsen og utviklingen er forsøkt satt i
sammenheng med hendelser på den norske kontinentalmarginen. De tre kanjonene er så
sammenliknet med Andøyakanjonen, som ligger noe lenger nord enn de tre kanjonene i
studieområdet
Sedimentary processes, late Cenozoic evolution and sediment yield on the continental margin offshore Troms, northern Norway
Full text linkPapers 2 and 3 of this thesis are not available in Munin: 2. Rydningen, T.A., Laberg, J.S., Kolstad, V.: 'Seabed morphology and sedimentary processes on high-gradient Trough Mouth Fans offshore Troms, northern Norway' (manuscript).3. Rydningen, T.A., Laberg, J.S., Kolstad, V.: 'Late Cenozoic evolution of high-gradient Trough Mouth Fans and canyons on the glaciated continental margin offshore Troms, northern Norway – palaeoclimatic implications and sediment yield' (manuscript)
Study of the Late Cenozoic depositional environment and seismic anomalies on the Trøndelag Platform using 3D seismic data
Full text linkThis thesis has focused on the depositional environment during the development of the Naust Formation in order to improve our understanding of the glacial history of the mid-Norwegian continental shelf, using 3D-seismic data from the Trænabanken and Sklinnadjupet area along with regional 2D-lines. Seismic anomalies have also been investigated to increase our understanding of fluid migration affecting the Naust Formation. A seismic stratigraphy of the area has been established and correlated to earlier works in adjacent areas, resulting in 5 seismostratigraphic units, N (oldest), A, U, S and T (youngest).
Eleven seismic horizons in different stratigraphic levels have been mapped for geomorphological features, identifying glacial features such as cross-shelf troughs, MSGL, flutes, hill-hole pairs and iceberg plough-marks. These features suggests a dynamic glacial history on the mid-Norwegian continental shelf over the past 2.8 Ma. Iceberg plough-marks have been identified early in Naust N time (1.5-2.8 Ma), which may indicate the presence of calving ice along the Norwegian coast. Morainal deposits along with an increase in deposition of debris flows suggest a change in depositional environment taking place during Naust N time, where glacial processes became more dominant. This may be the first indication of the ice sheet reaching the paleo-shelf edge within the study area. Cross-shelf troughs, MSGL and flutes have been located on the base of unit A, S and T as well as on the seafloor. This suggests the presence of several fast-flowing ice streams in the period from ~1.5 Ma to the last glacial maximum. The Vestfjorden paleo-ice stream appears to have reached all the way down to the Skjoldryggen area during the Elsterian glaciation. However, the buildup of Trænabanken probably resulted in a change in flow pattern during the two last glaciations, where the Vestfjorden paleo-ice stream drained throughout Trænadjupet while Sklinnadjupet was dominated by ice flowing from the east.
The massive loading by the thick glacial deposits of the Naust Formation resulted in polygonal faulting of the underlying Brygge Formation in the study area. This lead to dewatering, which may be the main source of fluids in the area along with fluids migrating through deep-seated faults from deeper sources. Vertical discontinuities in the seismic data suggests vertical fluid flow within pipes or through fractures created by overpressure within the Naust Formation, while some bright spots and paleo-pockmarks indicate that as the fluids encounter permeable layers the flow was freely following the stratigraphic boundaries of the prograding wedges
Sedimentary processes and paleoenvironments in Moskusoksefjord and Nordfjord, North-East Greenland.
Full text linkMulti-proxy analyses of five sediment cores (including lithostratigraphy, physical properties and XRF-scanning) and analyses of swath bathymetry and high resolution seismic data were integrated in order to reconstruct the Holocene glacial history and paleoenvironment of Moskusoksefjord and inner parts of Nordfjord, North-East Greenland.
In Moskusoksefjord, the large-scale bathymetry is divided into an inner-, middle- and outer basins, separated by relatively large deltas prograding into the fjord from both sides. Several slide scars and sediment lobes are also found, in addition to numerous channels. No glacial landforms have been observed in the study area apart from two transverse ridges in the outer basin of Moskusoksefjord which may represent buried glacial moraines. The seismostratigraphy revealed two main units with a stratified acoustic signature as well as MTDs of various dimensions. From their distribution, mass-transport activity in Moskusoksefjord and Nordfjord probably occurred episodically throughout the entire Holocene.
Suspension settling, as well as mass-transport deposits and ice-rafting from icebergs and sea-ice are the main sedimentary processes of both fjords. The two main sources of sediment were theWaltershausen Gletscher and the river coming from Badlandal at the fjord head of Moskusoksefjord. The estimated average sedimentation rates are 58 cm/ka for the last ~8 ka and 85-446 cm/ka for the last 1 ka. Ice-rafting was of higher relative importance with increasing influence away from the glacier margin. However, rafting of material from icebergs and sea ice has proven to be of less importance in the two studied fjords than in other East-Greenland fjords (cf. Smith and Andrews, 2000).
After retreating onto land during the warm Holocene Climate Optimum, Waltershausen Gletscher probably advanced into tidewater after a climate cooling ~6500 cal. yr. BP. An increase in the glacial activity continued through the Neoglaciation, with shorefast sea-ice suppressing iceberg rafting and an increase in the amount of laminations characterizing the time period. No clear glacial advance and little IRD are observed related to the Little Ice Age. In addition to the late cooling signal in the sediment cores, it is interpreted to indicate a late onset and a restricted advance of the Little Ice Age ice front in Moskusoksefjord and Nordfjord
Mass-movements on the continental slope offshore Lofoten, Northern Norway
No full textSwath bathymetry, side-scan sonar, sub-bottom profiler and seismic data from the continental slope offshore the Lofoten Islands, northern Norway reveal smaller-scale mass movements in water depths between 1100 and 2500 m. These mass movements have volumes of 0.061 to 8.7 km3 and are interpreted as translational slides involving spreading and multi-phase retrogression. The spatial variation in failure style is inferred to have been caused by the activation of different glideplanes (12.5-130 mbsf) within the thicker and more mounded contouritic deposits in the north-east of the study area.
Data from a sediment core show that the shallowest style of mass movement (12.5 mbsf), was initiated within contouritic sediments characterized by high sensitivities and water contents. This unit overlies a plumite interval characterized by dilative behavior with pore pressure decrease with increasing shear strain and high undrained shear strength. As such, it is the difference in geotechnical properties which indicates that the interface between these units acts as the basal glide plane, with deformation in the weaker overlying unit.
The mass movements in the study area are inferred to have been triggered by undercutting and removal of support at the foot of the slope due to large-scale mass movements that have occurred immediately south of the study area, such as the Trænadjupet or Nyk slides.
Furthermore, a network of 2D seismic data reveals the presence of several paleo-canyons. The data illustrate that canyon formation is more extensive then previously thought. These paleo-canyons are buried by an extensive contourite drift interpreted to be a continuation of the Lofoten Drift. The distribution of the drift indicates changes in the depth and strength of paleo-currents. Mass movements only occur in the upper part of the sequence, most likely after the onset of the Pleistocene
Cenozoic tectonosedimentary development and erosion estimates for the Barents Sea continental margin, Norwegian Arctic
No full textThe Barents Sea shelf has been experienced extensive uplift and erosion in the Cenozoic. However, the pre-glacial erosion has been so far less constrained in comparison to the glacial erosion. This paper aims to better understand the early–middle Cenozoic erosion in the western Barents Sea and the late Cenozoic erosion in the northern Barents Sea by using the mass-balance approach. The study utilizes seismic and well data to map the Cenozoic sediments and to estimate their volumes. The paleoenvironmental reconstruction is used to delineate the size of the likely source areas. From this, the average erosion and erosion rates are estimated. It is important to quantify the erosion as an effort to lower the risk in petroleum exploration in the Barents Sea. This study is also essential to understand the sedimentation pattern and their relation to the tectonic development. The paper suggests an N-S trending of uplift and erosion in the early–middle Cenozoic and E-W trending of uplift and erosion in the late Cenozoic. For the first time, the glacial erosion is estimated in the northeastern Svalbard/northern Barents Sea continental margin, which reflects the sediment input to the Arctic Ocean. The average erosion rates show one order of magnitude lower than the glacial erosion rates. The estimated numbers from this thesis are compared to the other high-latitude margins and in agreement with present-day systems
Reconstruction of late Holocene paleoenvironment in Kongsfjorden, West Spitsbergen. Based on analysis of benthic foraminifera
Full text linkThe benthic foraminiferal fauna of two marine sediment records from the Kongsfjorden Trough and the inner part of Kongsfjorden were analyzed to reconstruct the paleoenvironmental development throughout the last ~ 2000 years. A generally cold period is evident in both records, lasting from ~ 700 to 1400 CE at the Kongsfjorden Trough and from ~ 350 to 1200 CE in the inner part of Kongsfjorden, with low to moderate influence of Atlantic Water at both sites. However, the record from the inner part of Kongsfjorden show more fluctuating conditions, possibly due to high influence of local water masses. In both records, the cold period is followed by a period of ameliorated conditions, characterized by an abrupt increase of the benthic foraminiferal flux from ~ 1400 to 1650 CE at the Kongsfjorden Trough, and a gradual increase in the relative abundance of N. labradorica from ~ 1200 to 1550 CE in the inner part of Kongsfjorden. This indicates increased influence of Atlantic Water at both sites, and is correlated to correspond to the Medieval Warm Period. The record from the Kongsfjorden Trough stops at ~ 1650 CE as the core top is missing. In the inner part of Kongsfjorden a period of rapidly deteriorated conditions follows from ~ 1550 to 1650 CE, characterized by an abrupt increase of % E. excavatum f. clavata and a corresponding decrease of % N. labradorica. From ~ 1650 to 1900 CE the trend changes with gradually improved conditions. The period from ~ 1550 to 1900 CE is correlated to correspond to the Little Ice Age. The last ~ 100 years of the NP14-Kb3 record is characterized by an accelerated increase of % N. labradorica, reaching maxima in relative abundance. This possibly indicates the highest influence of Atlantic Water throughout the record, and is correlated to correspond to the Modern Warming
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