The tectonic origin of Planum Boreum spiral troughs, Mars

2020 ◽  
Author(s):  
Costanza Rossi ◽  
Paola Cianfarra ◽  
Francesco Salvini
Keyword(s):  
Tectonic Setting ◽  
Ice Sheet ◽  
Normal Faults ◽  
Origin And Evolution ◽  
Tectonic Model ◽  
Ice Cap ◽  
The North ◽  
Ice Sheet Dynamics ◽  
The Antarctic ◽  
Tectonic Origin

<p>The spiral troughs of the North Polar Layered deposits on Mars are deep depressions that dissect the Planum Boreum ice cap. These are enigmatic structures whose puzzling origin is still under debate. Advanced hypotheses on their genesis and evolution range between erosional to structural scenario. In this work, a double approach was followed to explore the structural/tectonic origin of the spiral troughs by means of Hybrid Cellular Automata (HCA) numerical modelling and lineament domain analysis. The SHARAD profile data were used to replicate the ice internal layering architecture associated to buried troughs in Gemina Lingula. Analysis of the lineament domains automatically detected at the ice surface from satellite images of the Mars Orbiter Camera strengthened the structural/tectonic interpretation of their origin and evolution. Similar, twofold approach was used for the investigation of a terrestrial analog identified in the Antarctic ice sheet. It presents at depth blind structures recognized as fractures/faults produced by ice sheet dynamics. Radargrams of Operation IceBridge mission and images from Sentinel-2 were used to produce a tectonic model that was in turn compared with the Planum Boreum one. Obtained results, and their comparison, show that the troughs of Gemina Lingula result from the activity of low-angle normal faults with listric geometry. The activity of listric faults is modelled and compared with the antarctic analog. At the surface the detected lineament domains confirm the tectonic setting by tracing the buried trough/fault orientations. The proposed tectonic model refers to extensional regime characterized by the presence of a deep detachment connecting the troughs at depth. This represents an internal ductile layer placed at depth greater than 1000 m whose kinematics induces the troughs/faults deformation. The extensional tectonics developed in Planum Boreum is possibly related to the ice cap collapse that induces internal dynamics. In this way, katabatic winds play a secondary role by maintaining at the surface the troughs nearly orthogonal to their directions.</p>

scholarly journals Antarctic Palaeotopography

2021 ◽  
pp. M56-2020-7
Author(s):  
Guy J. G. Paxman
Keyword(s):  
Ice Sheet ◽  
Future Research ◽  
Dynamic Topography ◽  
Antarctic Ice Sheet ◽  
Isostatic Adjustment ◽  
Subglacial Topography ◽  
Mantle Processes ◽  
Ice Sheet Dynamics ◽  
The Antarctic

AbstractThe development of a robust understanding of the response of the Antarctic Ice Sheet to present and projected future climatic change is a matter of key global societal importance. Numerical ice sheet models that simulate future ice sheet behaviour are typically evaluated with recourse to how well they reproduce past ice sheet behaviour, which is constrained by the geological record. However, subglacial topography, a key boundary condition in ice sheet models, has evolved significantly throughout Antarctica's glacial history. Since mantle processes play a fundamental role in the generation and modification of topography over geological timescales, an understanding of the interactions between the Antarctic mantle and palaeotopography is crucial for developing more accurate simulations of past ice sheet dynamics. This chapter provides a review of the influence of the Antarctic mantle on the long-term evolution of the subglacial landscape, through processes including structural inheritance, flexural isostatic adjustment, lithospheric cooling and thermal subsidence, volcanism and dynamic topography. The uncertainties associated with reconstructing these processes through time are discussed, as are important directions for future research and the implications of the evolving subglacial topography for the response of the Antarctic Ice Sheet to climatic and oceanographic change.

scholarly journals A high-resolution synthetic bed elevation grid of the Antarctic continent

2016 ◽  
Author(s):  
Felicity S. Graham ◽  
Jason L. Roberts ◽  
Ben K. Galton-Fenzi ◽  
Duncan Young ◽  
Donald Blankenship ◽  
...  
Keyword(s):  
High Resolution ◽  
Ice Sheet ◽  
Radar Data ◽  
Detailed Knowledge ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Bed Elevation ◽  
Antarctic Continent ◽  
Ice Sheet Dynamics ◽  
The Antarctic

Abstract. Digital elevation models of Antarctic bed topography are heavily smoothed and interpolated onto low-resolution (> 1 km) grids as our current observed topography data are generally sparsely and unevenly sampled. This issue has potential implications for numerical simulations of ice-sheet dynamics, especially in regions prone to instability where detailed knowledge of the topography, including fine-scale roughness, is required. Here, we present a high-resolution (100 m) synthetic bed elevation terrain for the whole Antarctic continent. The synthetic bed surface preserves topographic roughness characteristics of airborne and ground-based ice-penetrating radar data from the Bedmap1 compilation and the ICECAP consortium. Broad-scale features of the Antarctic landscape are incorporated using a low-pass filter of the Bedmap2 bed-elevation data. Although not intended as a substitute for Bedmap2, the simulated bed elevation terrain has applicability in high-resolution ice-sheet modelling studies, including investigations of the interaction between topography, ice-sheet dynamics, and hydrology, where processes are highly sensitive to bed elevations. The data are available for download at the Australian Antarctic Data Centre (doi:10.4225/15/57464ADE22F50).

Late-glacial flow patterns, deglaciation, and postglacial emergence of south-central Baffin Island and the north-central coast of Hudson Strait, eastern Canadian Arctic

1996 ◽  
Vol 33 (11) ◽  
pp. 1499-1510 ◽  
Author(s):  
William F. Manley
Keyword(s):  
High Tide ◽  
Ice Sheet ◽  
Late Glacial ◽  
Flow Patterns ◽  
Sediment Provenance ◽  
Radiocarbon Dates ◽  
Ice Cap ◽  
The North ◽  
South Central ◽  
Ice Stream

New georaorphic, sedimentologic, and chronologic data are used to reconstruct late Quaternary ice-sheet flow patterns, deglaciation, and isostatic uplift along the largest marine trough connecting the Laurentide Ice Sheet with the North Atlantic Ocean. The Lake Harbour region was targeted for study given its potential to record flow from several ice-dispersal centers. Striations and sediment provenance indicators define flow patterns. Thirty-four radiocarbon dates constrain a chronology of events. Centuries or millennia(?) before deglaciation, a southeast-flowing ice stream impinged on southernmost Big Island, as recorded by a single striation site and delimited in extent by geomorphic evidence of cold-based ice. During the Cockburn Substagc (9000–8000 BP), the region was scoured by southward to southwestward flow from an ice cap on Meta Incognita Peninsula, as recorded by 60 striation sites along 200 km of coastline. Carbonate erratics are uncommon in till above the marine limit. Where present, they suggest that southward flow reworked older drift. At about 8200 BP, the area was dcglaciated, and the marine limit was established at elevations of 67–141 m above high tide. Iceberg calving and sediment discharge from an ice margin in Ungava Bay, Hudson Bay, or Foxe Basin then blanketed the area with limestone-rich glaciomarinc sediment. Afterward, the region experienced slow but sustained emergence. The data revise the maximum lateral extent of a Late Wisconsinan ice stream in Hudson Strait and emphasize the extent of a late-glacial ice cap on western Meta Incognita Peninsula.

Antarctic Sedimentary Basins: defining crucial constraints on ice-sheet and solid-earth dynamic interactions

2021 ◽  
Author(s):  
Alan Aitken ◽  
Lu Li ◽  
Bernd Kulessa ◽  
Thomas Jordan ◽  
Joanne Whittaker ◽  
...  
Keyword(s):  
Sedimentary Rocks ◽  
Ice Sheet ◽  
Sedimentary Basins ◽  
Weddell Sea ◽  
Magnetic Data ◽  
West Antarctica ◽  
Antarctic Ice Sheet ◽  
Crystalline Bedrock ◽  
Ice Sheet Dynamics ◽  
The Antarctic

<p>Subglacial and ice-sheet marginal sedimentary basins have very different physical properties to crystalline bedrock and, therefore, form distinct conditions that influence the flow of ice above. Sedimentary rocks are particularly soft and erodible, and therefore capable of sustaining layers of subglacial till that may deform to facilitate fast ice flow downstream. Furthermore, sedimentary rocks are relatively permeable and thus allow for enhanced fluid flux, with associated impacts on ice-sheet dynamics, including feedbacks with subglacial hydrologic systems and transport of heat to the ice-sheet bed. Despite the importance for ice-sheet dynamics there is, at present, no comprehensive record of sedimentary basins in the Antarctic continent, limiting our capacity to investigate these influences. Here we develop the first version of an Antarctic-wide spatial database of sedimentary basins, their geometries and physical attributes. We emphasise the definition of in-situ and undeformed basins that retain their primary characteristics, including relative weakness and high permeability, and therefore are more likely to influence ice sheet dynamics. We define the likely extents and nature of sedimentary basins, considering a range of geological and geophysical data, including: outcrop observations, gravity and magnetic data, radio-echo sounding data and passive and active-source seismic data. Our interpretation also involves derivative products from these data, including analyses guided by machine learning. The database includes for each basin its defining characteristics in the source datasets, and interpreted information on likely basin age, sedimentary thickness, surface morphology and tectonic type. The database is constructed in ESRI geodatabase format and is suitable for incorporation in multifaceted data-interpretation and modelling procedures. It can be readily updated given new information. We define extensive basins in both East and West Antarctica, including major regions in the Ross and Weddell Sea embayments and the Amundsen Sea region of West Antarctica, and the Wilkes, Aurora and Recovery subglacial basins of East Antarctica. The compilation includes smaller basins within crystalline-bedrock dominated areas such as the Transantarctic Mountains, the Antarctic Peninsula and Dronning Maud Land. The distribution of sedimentary basins reveals the combined influence of the tectonic and glacial history of Antarctica on the current and future configuration of the Antarctic Ice Sheet and highlights areas in which the presence of dynamically-evolving subglacial till layers and the exchange of groundwater and heat with the ice sheet bed  are more likely, contributing to dynamic behaviour of the Antarctic Ice Sheet.  </p>

Subsidence discrepancy in the Valencia Trough revealed from reflection seismic observations and backstripping results

2020 ◽  
Author(s):  
Penggao Fang ◽  
Geoffroy Mohn ◽  
Julie Tugend ◽  
Nick Kusznir
Keyword(s):  
Tectonic Setting ◽  
Temporal Distribution ◽  
Drill Hole ◽  
Western Mediterranean ◽  
Normal Faults ◽  
Seismic Profiles ◽  
Gulf Of Lions ◽  
North West ◽  
The North ◽  
Valencia Trough

<p>    The Valencia Trough is commonly included as part of the set of western Mediterranean Cenozoic extensional basins that formed in relation with the Tethyan oceanic slab rollback during the latest Oligocene to early Miocene. It lies in a complex tectonic setting between the Gulf of Lions to the North-West, the Catalan Coastal Range and the Iberian chain to the West, the Balearic promontory to the East and the Betic orogenic system to the South. This rifting period is coeval with or directly followed by the development of the external Betics fold and thrust belts at the southern tip of the Valencia Trough. Recent investigations suggest that the Valencia Trough is segmented into two main domains exhibiting different geological and geophysical characteristics between its northeastern and southwestern parts. The presence of numerous Cenozoic normal faults and the well-studied subsidence pattern evolution of the NE part of the Valencia Trough suggest that it mainly formed coevally with the rifting of Gulf of Lion. However, if a significant post-Oligocene subsidence is also evidenced in its SW part; fewer Cenozoic rift structures are observed suggesting that the subsidence pattern likely results from the interference of different processes.</p><p>    In this presentation, we quantify the post-Oligocene subsidence history of the SW part of the Valencia Trough with the aim of evaluating the potential mechanisms explaining this apparent subsidence discrepancy. We analyzed the spatial and temporal distribution of the post-Oligocene subsidence using the interpretation of a dense grid of high-quality multi-channel seismic profiles, also integrating drill-hole results and velocity information from expanding spread profiles (ESP). We used the mapping of the main unconformities, especially the so-called Oligocene unconformity, to perform a 3D flexural backstripping, which permits the prediction of the post-Oligocene water-loaded subsidence. Our results confirm that the post-Oligocene subsidence of the SW part of the Valencia Trough cannot be explained by the rifting of the Gulf of Lions. Previous works already showed that the extreme crustal thinning observed to the SW is related to a previous Mesozoic rift event. Here, we further highlight that if few Cenozoic extensional structures are observed, they can be interpreted as gravitational features rooting at the regionally identified Upper Triassic evaporite level. Backstripping results combined with the mapping of the first sediments deposited on top of the Oligocene unconformity show that they are largely controlled by the shape of Betic front with a possible additional effect of preserved Mesozoic structures. At larger scale, we compare the mechanisms accounting for the origin and subsidence at the SW part of the Valencia Trough with those responsible for the subsidence of its NE part and the Gulf of Lions.</p>

scholarly journals The implications of the Pineo Ridge readvance in Maine

2011 ◽  
Vol 31 (3-4) ◽  
pp. 203-206 ◽  
Author(s):  
Harold W. Borns ◽  
Terence J. Hughes
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Bay Of Fundy ◽  
Great Lakes Region ◽  
Ice Streams ◽  
Ice Caps ◽  
Major Consequence ◽  
Ice Cap ◽  
The North

Much of the Laurentide ice sheet in Maine, Atlantic Provinces, and southern Quebec was a "marine ice sheet," that is it was grounded below the prevailing sea level. When proper conditions prevailed, calving bays progressed into the ice sheet along ice streams partitioning it, leaving those portions grounded above sea level as residual ice caps. At least by 12,800 yrs. BP a calving bay had progressed up the St. Lawrence Lowland at least to Ottawa while a similar, but less extensive calving bay developed in Central Maine at approximately the same time. Concurrently, ice draining north into the St. Lawrence and south into the Central Maine calving bays rapidly lowered the surface of the intervening ice sheet until it eventually divided over the NE-SW trending Boundary and Longfellow Mountains and probably over other highland areas as well. A major consequence of these nearly simultaneous processes was the separation of an initial large ice cap over part of Maine, New Brunswick, and Québec which was bounded on the west by the calving bay in Central Maine, to the north by the calving bay in the St. Lawrence Lowland, to the south by the Bay of Fundy, and to the east by the Gulf of St. Lawrence. In coastal Maine, east of the calving bay, the margin of the ice cap receded above the marine limit at least 40 km and subsequently read-vanced terminating at Pineo Ridge moraine approximately 12,700 yrs. BP. These events are the stratigraphie and chronologic equivalent of the Cary-Pt. Huron recession/Pt. Huron readvance of the Great Lakes region.

Late Quaternary Iceberg Rafting along the Antarctic Peninsula Continental Rise and in the Weddell and Scotia Seas

2001 ◽  
Vol 56 (3) ◽  
pp. 308-321 ◽  
Author(s):  
Colm Ó Cofaigh ◽  
Julian A. Dowdeswell ◽  
Carol J. Pudsey
Keyword(s):  
Antarctic Peninsula ◽  
Late Quaternary ◽  
Sediment Cores ◽  
Regional Scale ◽  
Ice Sheet ◽  
Glacial Cycles ◽  
Continental Rise ◽  
The North ◽  
Glacial Periods ◽  
The Antarctic

AbstractSediment cores from the continental rise west of the Antarctic Peninsula and the northern Weddell and Scotia Seas were investigated for their ice-rafted debris (IRD) content by lithofacies logging and counting of particles >0.2 cm from core x-radiographs. The objective of the study was to determine if there are iceberg-rafted units similar to the Heinrich layers of the North Atlantic that might record periodic, widespread catastrophic collapse of basins within the Antarctic Ice Sheet during the Quaternary. Cores from the Antarctic Peninsula margin contain prominent IRD-rich units, with maximum IRD concentrations in oxygen isotope stages 1, 5, and 7. However, the greater concentration of IRD in interglacial stages is the result of low sedimentation rates and current winnowing, rather than regional-scale episodes of increased iceberg rafting. This is also supported by markedly lower mass accumulation rates (MAR) during interglacial periods versus glacial periods. Furthermore, thinner IRD layers within isotope stages 2–4 and 6 cannot be correlated between individual cores along the margin. This implies that the ice sheet over the Antarctic Peninsula did not undergo widespread catastrophic collapse along its western margin during the late Quaternary (isotope stages 1–7). Sediment cores from the Weddell and Scotia Seas are characterized by low IRD concentrations throughout, and the IRD signal generally appears to be of limited regional significance with few strong peaks that can be correlated between cores. Tentatively, this argues against pervasive, rapid ice-sheet collapse around the Weddell embayment over the last few glacial cycles.

scholarly journals I.—The Antarctic Ice-cap

1906 ◽  
Vol 3 (12) ◽  
pp. 529-534
Author(s):  
H. T. Ferrar
Keyword(s):  
Ice Sheet ◽  
Ice Caps ◽  
Ice Cap ◽  
Main Support ◽  
Glacial Periods ◽  
The Antarctic ◽  
Geological Magazine

In a recent number of the Geological Magazine, Dec. V, Vol. III, March, 1906, p. 120, there is an article by Prof. E. H. L. Schwarz which deals with the thickness of ice-caps during the various Glacial periods. At the outset Professor Schwarz takes the data furnished by Captain Scott's narrative of the voyage of the “Discovery” as the main support of the physicists' contention that an ice-sheet cannot exceed 1,600 feet in thickness.

scholarly journals The Dynamics of Marine Ice Sheets

1979 ◽  
Vol 24 (90) ◽  
pp. 167-177 ◽  
Author(s):  
Robert H. Thomas
Keyword(s):  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Shelves ◽  
The North ◽  
West Antarctic ◽  
Grounding Line ◽  
Ice Sheet Dynamics

AbstractMarine ice sheets rest on land that, for the most part, is below sea-level. Ice that flows across the grounding line, where the ice sheet becomes afloat, either calves into icebergs or forms a floating ice shelf joined to the ice sheet. At the grounding line there is a transition from ice-sheet dynamics to ice-shelf dynamics, and the creep-thinning rate in this region is very sensitive to sea depth; rising sea-level causes increased thinning-rates and grounding-line retreat, falling sea-level has the reverse effect. If the bedrock slopes down towards the centre of the ice sheet there may be only two stable modes: a freely-floating ice shelf or a marine ice sheet that extends to the edge of the continental shelf. Once started, collapse of such an ice sheet to form an ice shelf may take place extremely rapidly. Ice shelves which form in embayments of a marine ice sheet, or which are partially grounded, have a stabilizing influence since ice flowing across the grounding line has to push the ice shelf past its sides. Retreat of the grounding line tends to enlarge the ice shelf, which ultimately may become large enough to prevent excessive outflow from the ice sheet so that a new equilibrium grounding line is established; removal of the ice shelf would allow retreat to continue. During the late-Wisconsin glacial maximum there may have been marine ice sheets in the northern hemisphere but the only current example is the West Antarctic ice sheet. This is buttressed by the Ross and Ronne Ice Shelves, and if climatic warming were to prohibit the existence of these ice shelves then the ice sheet would collapse. Field observations suggest that, at present, the ice sheet may be advancing into parts of the Ross Ice Shelf. Such advance, however, would not ensure the security of the ice sheet since ice streams that drain to the north appear to flow directly into the sea with little or no ice shelf to buttress them. If these ice streams do not flow over a sufficiently high bedrock sill then they provide the most likely avenues for ice-sheet retreat.

scholarly journals Antarctica Gets a New Gravity Map

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Sarah Stanley
Keyword(s):  
Ice Sheet ◽  
Comprehensive Collection ◽  
Ice Sheet Dynamics ◽  
Gravity Map ◽  
The Antarctic

A comprehensive collection of variation in Earth's gravity could aid studies of the Antarctic geoid and of Antarctica's geology and ice sheet dynamics.

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