scholarly journals Glacio-lacustrine sedimentation in newly discovered paleo-lakes, Westland, New Zealand

2021 ◽  
Author(s):  
◽  
Adam Michael Thomas
Keyword(s):  
New Zealand ◽  
Glacial Lake ◽  
Glacial Retreat ◽  
Sedimentary Sequences ◽  
Quaternary Glaciation ◽  
Lake Formation ◽  
Landscape Response ◽  
Facies Succession ◽  
Lacustrine Facies ◽  
Depositional Models

<p>The remnant effects of Quaternary glaciation dominate the geomorphology of South Westland, New Zealand. Well-constrained glaciogenic records for the Last Glacial Maximum (LGM) (~MIS 2) show ice to have extended significant distances across the Westland piedmont, becoming tidewater calving in places. Despite clear evidence for glacial advance, landscape response to glacial retreat remains relatively poorly understood, with few described sedimentary sequences clearly recording deglaciation processes. A 240-metre thick glacio-lacustrine sedimentary sequence intercepted by drilling in the Whataroa Valley (DFDP-2) provides the first compelling evidence of pro-glacial lake formation in response to glacial retreat in Westland. To understand the vertical facies succession observed in this sequence, two glacio-lacustrine facies schemes and depositional models were developed. To do this, previously unmapped glacio-lacustrine sedimentary sequences in the Westland region underwent detailed sedimentological analysis to identify key glacio-lacustrine facies. In the Waitangitaona and Arahura river valleys, the presence of glacio-lacustrine sequences is also used to mark paleo-lake formation in the respective catchments.   Using the facies scheme and depositional models, together with 14C chronology and sedimentological analysis, a series of conclusions are developed from the DFDP-2 sequence: 1) Deposition occurred in an over-deepened glacial trough, with the sequence consisting of a basal diamictite, overlain by a ~ 140-metre interval of lacustrine  siltstones and sandstones. 2) The lower ~ 180-metres of sediment accumulated in 659 ± 151 yrs between 16609 ± 151 and 15994 ± 94 cal. yr BP, as the depositional environment at the drill-site evolved from an ice contact to an ice distal lacustrine setting. 3) Extremely rapid sedimentation rates, as well as high lake levels allowed the preservation of glacially over-steepened bedrock slopes beneath the Whataroa Valley.   The formation of a previously unknown, ~190 km2 pro-glacial lake on the Whataroa piedmont is inferred from the DFDP-2 sequence, with lake formation causing accelerated glacial retreat from the late LGM maxima. The presence of several catchments with comparable piedmont geometry suggests pro-glacial lake formation may have been a common response to glacial retreat in Westland. For a period, pro-glacial lakes may have been a significant transitory feature on the Westland landscape.</p>

scholarly journals Glacio-lacustrine sedimentation in newly discovered paleo-lakes, Westland, New Zealand

2021 ◽  
Author(s):  
◽  
Adam Michael Thomas
Keyword(s):  
New Zealand ◽  
Glacial Lake ◽  
Glacial Retreat ◽  
Sedimentary Sequences ◽  
Quaternary Glaciation ◽  
Lake Formation ◽  
Landscape Response ◽  
Facies Succession ◽  
Lacustrine Facies ◽  
Depositional Models

<p>The remnant effects of Quaternary glaciation dominate the geomorphology of South Westland, New Zealand. Well-constrained glaciogenic records for the Last Glacial Maximum (LGM) (~MIS 2) show ice to have extended significant distances across the Westland piedmont, becoming tidewater calving in places. Despite clear evidence for glacial advance, landscape response to glacial retreat remains relatively poorly understood, with few described sedimentary sequences clearly recording deglaciation processes. A 240-metre thick glacio-lacustrine sedimentary sequence intercepted by drilling in the Whataroa Valley (DFDP-2) provides the first compelling evidence of pro-glacial lake formation in response to glacial retreat in Westland. To understand the vertical facies succession observed in this sequence, two glacio-lacustrine facies schemes and depositional models were developed. To do this, previously unmapped glacio-lacustrine sedimentary sequences in the Westland region underwent detailed sedimentological analysis to identify key glacio-lacustrine facies. In the Waitangitaona and Arahura river valleys, the presence of glacio-lacustrine sequences is also used to mark paleo-lake formation in the respective catchments.   Using the facies scheme and depositional models, together with 14C chronology and sedimentological analysis, a series of conclusions are developed from the DFDP-2 sequence: 1) Deposition occurred in an over-deepened glacial trough, with the sequence consisting of a basal diamictite, overlain by a ~ 140-metre interval of lacustrine  siltstones and sandstones. 2) The lower ~ 180-metres of sediment accumulated in 659 ± 151 yrs between 16609 ± 151 and 15994 ± 94 cal. yr BP, as the depositional environment at the drill-site evolved from an ice contact to an ice distal lacustrine setting. 3) Extremely rapid sedimentation rates, as well as high lake levels allowed the preservation of glacially over-steepened bedrock slopes beneath the Whataroa Valley.   The formation of a previously unknown, ~190 km2 pro-glacial lake on the Whataroa piedmont is inferred from the DFDP-2 sequence, with lake formation causing accelerated glacial retreat from the late LGM maxima. The presence of several catchments with comparable piedmont geometry suggests pro-glacial lake formation may have been a common response to glacial retreat in Westland. For a period, pro-glacial lakes may have been a significant transitory feature on the Westland landscape.</p>

Detection of large, Holocene earthquakes using diatom analysis of coastal sedimentary sequences, Wellington, New Zealand

2007 ◽  
Vol 26 (7-8) ◽  
pp. 1129-1147 ◽  
Author(s):  
Ursula Cochran ◽  
Michael Hannah ◽  
Margaret Harper ◽  
Russ Van Dissen ◽  
Kelvin Berryman ◽  
...  
Keyword(s):  
New Zealand ◽  
Diatom Analysis ◽  
Sedimentary Sequences

scholarly journals Identification of Locations for Potential Glacial Lakes Formation using Remote Sensing Technology

2013 ◽  
Vol 12 ◽  
pp. 10-16
Author(s):  
P Yagol ◽  
A Manandhar ◽  
P Ghimire ◽  
RB Kayastha ◽  
JR Joshi
Keyword(s):  
Remote Sensing ◽  
Glacial Lake ◽  
Glacial Lakes ◽  
Outburst Flood ◽  
Remote Sensing Technology ◽  
Sensing Technology ◽  
Lake Formation ◽  
Significant Area ◽  
Glacial Lake Outburst Flood

In past Nepal has encountered a number of glacial lake outburst flood (GLOF) events causing loss of billions of rupees. Still there are a number of glacial lakes forming and there are chances of new glacial lake formation. Hence there is intense need to monitor glaciers and glacial lakes. The development on remote sensing technology has eased the researches on glacier and glacial lakes. Identification of locations of potential glacial lakes through the use of remote sensing technology has been proven and hence is opted for identification of locations of potential glacial lake in Khumbu Valley of Sagarmatha Zone, Nepal. The probable sites for glacial lake formation are at Ngojumpa, Lobuche, Khumbu, Bhotekoshi, Inkhu, Kyasar, Lumsumna, etc. As per study, the biggest glacial lake could form at Ngozumpa glacier. Even in other glaciers potential supra-glacial lakes could merge together to form lakes that occupy significant area. Nepalese Journal on Geoinformatics -12, 2070 (2013AD): 10-16

scholarly journals Detection of Large Holocene Earthquakes in the Sedimentary Record of Wellington, New Zealand, Using Diatom Analysis

2021 ◽  
Author(s):  
◽  
Ursula Alyson Cochran
Keyword(s):  
New Zealand ◽  
Late Holocene ◽  
Weighted Averaging ◽  
Diatom Analysis ◽  
Sedimentary Record ◽  
Sedimentary Sequences ◽  
Quantitative Estimates ◽  
Modern Analogue ◽  
Environmental Transitions ◽  
Large Earthquakes

<p>New Zealand is situated on the boundary between the Pacific and Australian tectonic plates. The Wellington region lies near the southern end of the Hikurangi subduction zone and within a zone of major, active strike-slip faults. Wellington's paleoseismic and historic records indicate that large surface rupture earthquakes have occurred on these faults in the past. Development of a complete record of past large earthquakes is a high priority for the region because of the risk posed by occurrence of large earthquakes in the future. The existing paleoseismic record has been derived predominantly from studies of fault trench stratigraphy, raised beach ridges and offset river terraces. The sedimentary record of lakes and coastal waterbodies is a source of information that has not been used specifically for paleoseismic purposes in the region. Therefore investigation of Wellington's sedimentary record is used in this thesis to make a contribution to the paleoseismic record. Holocene sedimentary sequences are studied from three small, low elevation, coastal waterbodies: Taupo Swamp, Okupe Lagoon and Lake Kohangapiripiri. Sequences of between 200 and 650 cm depth were collected using a hand-operated coring device. Sedimentology and diatom microfossil content were analysed and interpreted to enable reconstruction of paleoenvironment at each site. Radiocarbon dating was used to provide chronologies for the sequences that are aged between 5000 and 7500 calibrated years before present (cal. years BP). Diatom analysis is the main tool used to reconstruct paleoenvironment and detect evidence for occurrence of past large earthquakes. To aid reconstruction of sedimentary sequences used in this project, as well as coastal sequences in New Zealand in general, a coastal diatom calibration set was constructed using 50 sites around New Zealand. Modern diatom distribution and abundance, and associated environmental variables are analysed using ordination and weighted averaging techniques. Detrended correspondence analysis arranges species according to salinity preferences and divides sites clearly into waterbody types along a coastal gradient. This analysis enables reconstruction of waterbody type from fossil samples by passive placement onto ordination diagrams. Weighted averaging regression of calibration set samples results in a high correlation (r2jack=0.84) between observed and diatom inferred salinity, and enables salinity preferences and tolerances to be derived for 100 species. This confirms for the first time that species' preferences derived in the Northern Hemisphere are generally applicable to diatoms living in the coastal zone of New Zealand. Weighted averaging calibration and the modern analogue technique are used to generate quantitative estimates of paleosalinity for fossil samples. Paleoenvironmental reconstructions of Taupo Swamp, Okupe Lagoon and Lake Kohangapiripiri indicate that each waterbody has been isolated from the sea during the late Holocene. Isolation has been achieved through interplay of sediment accumulation causing growth of barrier beaches, and coseismic uplift. Ten distinct transitions between different paleoenvironments are recognised from the three sequences. These transitions involve changes in relative sea level or water table level often in association with catchment disturbance or marine influx events. All transitions occur suddenly and are laterally extensive and synchronous within each waterbody. Quantitative estimates of paleosalinity and waterbody type are used to differentiate between large and small magnitude changes in paleoenvironment. Five transitions involve large amounts of paleoenvironmental change and provide evidence for earthquakes occurring at approximately 5200, approximately 3200, and approximately 2300 cal. years BP. Five other transitions are consistent with the effects of large earthquakes occurring at approximately 6800, 2200, approximately 1000, approximately 500 cal. years BP and 1855 AD but do not provide independent evidence of the events. Environmental transitions at Lake Kohangapiripiri clarify the timing of rupture of the Wairarapa Fault by bracketing incompatible age estimates derived from two different sites on the fault. The oldest environmental transitions recognised at Taupo Swamp and Okupe Lagoon both occur at approximately 3200 cal. years BP indicating that western Wellington was uplifted at this time. Environmental transitions are recorded at all three study sites at approximately 2300 cal. years BP indicating that the entire western and central Wellington region experienced coseismic uplift at this time. Because of the distance between sites this apparent synchroneity implies that several faults in the region ruptured at a similar time. Investigation of sedimentary sequences contributes to the existing paleoseismic record by providing additional estimates of timing for past large earthquakes, enabling estimation of the areal extent of the effects of past earthquakes, and by highlighting periods of fault rupture activity in the late Holocene.</p>

Stratification models for vegetated coastal dunes in Atlantic Canada

1989 ◽  
Vol 96 ◽  
pp. 203-215
Author(s):  
S. B. McCann ◽  
M.-L. Byrne
Keyword(s):  
Internal Structure ◽  
Coastal Dunes ◽  
Atlantic Canada ◽  
Sedimentary Sequences ◽  
Plant Associations ◽  
Depositional Settings ◽  
Aeolian Activity ◽  
Depositional Models

SynopsisThe principal types of stratification and some characteristic sedimentary sequences found in vegetated coastal dunes in Atlantic Canada are described. Four examples are selected to show a range of dune types and depositional settings. In each case the documentation and interpretation of the internal structure and stratification has made an important contribution to understanding the evolution of the dunes. Stratification and depositional models are presented for:(1) a single, continuous, transgressive foredune ridge which maintains its form during transgression;(2) a discontinuous transgressive foredune ridge, interrupted by washover passages;(3) a “precipitation” dune, which buries an existing stable dune; and(4) complex dunes produced by two or more phases of aeolian activity characterised by different plant associations.

Reconstruction of Early Holocene jokulhlaups along the Hvita River and Gullfoss waterfall, Iceland

2020 ◽  
Author(s):  
Greta Wells ◽  
Þorsteinn Sæmundsson ◽  
Sheryl Luzzadder-Beach ◽  
Timothy Beach ◽  
Andrew Dugmore
Keyword(s):  
Ice Sheet ◽  
Hydraulic Modeling ◽  
Early Holocene ◽  
Glacial Lake ◽  
Exposure Dating ◽  
Alpine Regions ◽  
Outburst Floods ◽  
Lake Formation ◽  
Geothermal Activity ◽  
Downstream Communities

&lt;p&gt;Glacial lake outburst floods (GLOFs) have occurred across the planet throughout the Quaternary and are a significant geohazard in Arctic and alpine regions today. Iceland experiences more frequent GLOFs&amp;#8212;known in Icelandic as j&amp;#246;kulhlaups&amp;#8212;than nearly anywhere on Earth, yet most research focuses on floods triggered by subglacial volcanic and geothermal activity. However, floods from proglacial lakes may be a better analogue to most global GLOFs.&lt;/p&gt;&lt;p&gt;As the Icelandic Ice Sheet retreated across Iceland in the Late Pleistocene-Early Holocene, meltwater pooled at ice margins and periodically drained in j&amp;#246;kulhlaups. Some of the most catastrophic floods drained from ice-dammed Glacial Lake Kj&amp;#246;lur, surging across southwestern Iceland from the interior highlands to the Atlantic Ocean. These floods left extensive geomorphologic evidence along the modern-day course of the Hv&amp;#237;t&amp;#225; River, including canyons, scoured bedrock, boulder deposits, and Gullfoss&amp;#8212;Iceland&amp;#8217;s most famous waterfall. The largest events reached an estimated maximum peak discharge of 300,000 m&lt;sup&gt;3&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;, ranking them among the largest known floods in Iceland and on Earth.&lt;/p&gt;&lt;p&gt;Yet, all our evidence for the Kj&amp;#246;lur j&amp;#246;kulhlaups comes from only one publication to date (T&amp;#243;masson, 1993). My research employs new methods to better constrain flood timing, routing, magnitude, and recurrence interval at this underexplored site. This talk presents new and synthesized j&amp;#246;kulhlaup geomorphologic evidence; HEC-RAS hydraulic modeling results of flow magnitude and routing; and ongoing geochronological analyses using cosmogenic nuclide exposure dating and tephrochronology. It also situates these events within Icelandic Ice Sheet deglaciation chronology and environmental change at the Pleistocene-Holocene transition. Finally, it examines the Kj&amp;#246;lur floods as an analogue to contemporary ice sheet response, proglacial lake formation, and j&amp;#246;kulhlaup processes and landscape evolution in Arctic and alpine regions worldwide, where GLOFs pose an increasing risk to downstream communities due to climate-driven meltwater lake expansion. &amp;#160;&lt;/p&gt;&lt;p&gt;Citation: T&amp;#243;masson, H., 1993. J&amp;#246;kulst&amp;#237;flu&amp;#240; v&amp;#246;tn &amp;#225; Kili og hamfarahlaup &amp;#237; Hv&amp;#237;t&amp;#225; &amp;#237; &amp;#193;rness&amp;#253;slu. N&amp;#225;tt&amp;#250;rufr&amp;#230;&amp;#240;ingurinn 62, 77-98.&lt;/p&gt;

scholarly journals A conceptual model of supra-glacial lake formation on debris-covered glaciers based on GPR facies analysis

2016 ◽  
Vol 42 (6) ◽  
pp. 903-914 ◽  
Author(s):  
Jordan R. Mertes ◽  
Sarah S. Thompson ◽  
Adam D. Booth ◽  
Jason D. Gulley ◽  
Douglas I. Benn
Keyword(s):  
Conceptual Model ◽  
Facies Analysis ◽  
Glacial Lake ◽  
Lake Formation
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