Northern Antarctic Peninsula Research Articles

Transpressional deformation along the margin of Larsen Basin: new data from Pedersen Nunatak, Antarctic Peninsula

New structural data from the northern Antarctic Peninsula suggest that reverse faults and folds affecting the Pedersen Nunatak beds of the upper Mesozoic–Lower Cenozoic Larsen Basin succession were produced by transpressional forces acting parallel to the Weddell Sea coast of the Antarctic Peninsula during mid-Cretaceous compression of the Larsen Basin. At Pedersen Nunatak, Larsen Basin rocks are deformed into a series of synclines and anticlines that are cut by reverse faults.

Stratigraphy and age of the Lower Cretaceous Pedersen Formation, northern Antarctic Peninsula

The Pedersen Formation includes conglomerate-dominated successions exposed on Pedersen Nunatak (142 m thick) and southern Sobral Peninsula (750–1000 m thick). As re-defined here, it also includes mudstone and sandstone in tectonic contact with Nordenskjöld Formation strata on a nunatak north of the Sobral Peninsula conglomerate outcrops. 40Ar/39Ar ages and palynological data indicate an early Aptian age for the lower part of the formation on Sobral Peninsula. The Pedersen Nunatak strata have yielded conflicting age determinations, although an Early Cretaceous age seems likely. The Sobral Peninsula conglomerates are lithologically similar to, and possibly coeval with, basal Gustav Group strata (Lagrelius Point Formation) on James Ross Island. Although further field sampling is required to resolve the age of the Pedersen Nunatak strata, on present evidence the Pedersen Formation appears to form part of the same tectono-stratigraphic unit as the lower part of the Gustav Group, and we therefore propose that it be included in that group.

First Carboniferous and ?Permian marine macrofaunas from Antarctica and their tectonic implications

The first Carboniferous and ?Permian marine macrofaunas from the Antarctic continent are described from three sites near Mount King, Alexander Island, Antarctic Peninsula. They include bivalves, brachiopods, bryozoans, crinoids, gastropods, a possible monoplacophoran, nautiloids and a possible serpulid or microconchid. Overall the faunas of two localities are Carboniferous in age and compare well with the Levipustula levis Zone of Argentina and eastern Australia, and are of Namurian (Serpukhovian–Bashkirian) age, based mainly on the brachiopod and bryozoan faunas. Less positive brachiopod evidence from a third locality indicates the presence of a linoproductid fauna of possible Carboniferous or Permian (Gzhelian–Artinskian) age, having affinities with the Argentinian Cancrinella fauna. The lithological and structural characteristics of the Mount King beds are comparable to the accretionary complex of the LeMay Group (hitherto of only proven Jurassic–Cretaceous age) of Alexander Island, in which they are provisionally placed. However, the beds may also correlate with the Trinity Peninsula Group (Carboniferous–Triassic) of the northern Antarctic Peninsula. The features of the Mount King beds are consistent with the presence of an accretionery complex related to an island arc in the Late Palaeozoic, but are not necessarily conclusive proof of the presence of such a terrane at that time in what is now Alexander Island.

Breaking Up Is Easy

CLIMATOLOGY Several peripheral ice shelves have disappeared from the northern Antarctic Peninsula during the past few decades, most likely as a result of strong regional warming. The breakup of these shelves has occurred much more quickly, however, than would be expected if it were due simply to a

Bransfield Basin fine-grained sediments: late-Holocene sedimentary processes and Antarctic oceanographic conditions

The Antarctic Peninsula is sensitive to climatic change due to its northerly position and to the relatively reduced volume and character of its ice cover. High-resolution palaeoclimatic records from the Ant arctic Peninsula ice cores extend back only 500 years. A climatic record of 2850 years in the Bransfield Basin is investigated through the analysis of sediment gravity cores from the floor of the central subbasin (core GEBRA-1) and the slope of the eastern subbasin (core GEBRA-2). Sedimentological, mineralogical and geo chemical properties have been systematically measured, together with Accelerator Mass Spectrometry (AMS) radiocarbon dating. The fine-grained sediments result from two main processes: hemipelagic settling from resuspensions and primary productivity, and turbidity currents. Hemipelagic sediments were selected to investi gate the oceanographic and climatic conditions of the northern Antarctic Peninsula region during the last three millennia. Cold climatic periods are characterized by millimetric laminations and/or black layers with higher organic carbon, nitrogen and opal contents. Warm periods are recorded as massive to diffuse laminated facies with lower biogenic contents. The results include the ‘Little Ice Age’ (LIA) cold pulse as well as several 200– 300 year long fluctuations within the LIA and before this major climatic event of the Holocene.

The fossil record of Cunoniaceae: new evidence from Late Cretaceous wood of Antarctica?

Fossil angiosperm wood from Upper Cretaceous sediments of Livingston Island and James Ross Island in the northern Antarctic Peninsula region is identified as having the combination of anatomical characters most similar to modern Cunoniaceae. The material is characterised by predominantly solitary vessels, opposite to scalariform intervessel pitting, scalariform perforation plates, heterocellular multiseriate and homocellular uniseriate rays, diffuse axial parenchyma. Anatomically, the specimens conform most closely to the fossil organ genus Weinmannioxylon Petriella which has been placed within the Cunoniaceae. The presence of Weinmannioxylon in Late Cretaceous sediments suggests that taxa within or stem taxa to the Cunoniaceae might have been a notable component of the forest vegetation that covered the Antarctic Peninsula during the Late Mesozoic and may therefore represent the earliest record of this family.

Antarctic Peninsula Late Cretaceous-Early Cenozoic pal˦oenvironments and Gondwana pal˦ogeographies

A review is made of stratigraphical, geochemical and pal˦ogeographical data from the northern Antarctic Peninsula and the Southern Ocean for Late Mesozoic-Early Cenozoic times. Clay mineral and S/total organic C ratios are used to re-assess earlier scenarios, and it is suggested that eight climatic episodes affected the northern Antarctic Peninsula between Late Aptian and Pal˦ogene times. Evolving pal˦ogeographies in southern Gondwana allowed the connection of the inter-continental western Weddell Basin to the proto-Indian Ocean during Albian to Cenomanian times, and it is suggested that this caused an initial cooling of ambient temperatures in the northern Antarctic Peninsula area. This situation altered when the South Atlantic seaway was opened to equatorial regions, producing a Campanian warm episode. Throughout this period, the climate was humid and non-seasonal (ever-wet) and the adjacent seas were dominated by mineralwalled phytoplankton. A Maastrichtian to Mid-Pal˦ocene cool period is postulated following the establishment of more-polar ocean circulation routes along the southern edge of the Pacific Basin, and the climate became seasonally humid with phytoplankton production switching to organicwalled dominant. The global Pal˦ogene climatic optimum was a warm, ever-wet episode but as it waned from Mid-Eocene times, a further, relatively short, period of marked seasonality is recognised. Later, Eocene climates were again ever-wet and became progressively cooler. The Late Eocene-Early Oligocene opening of the Tasman Sea and Drake Passage seaways caused cold conditions on Seymour Island, followed rapidly by the earliest glacial sediments on King George Island and the establishment of mineral-walled phytoplankton dominance in the seas.

Seismicity and tectonics around the northern Antarctic Peninsula from King Sejong station data

Local earthquakes recorded at the King Sejong station (62° 13′31″S, 58° 47′07″W) from 1995–96 have been analysed to study the seismicity and tectonics around the northern Antarctic Peninsula. The nature of shallow-focused normal fault earthquakes along the South Shetland Platform is still unclear. Dominant normal fault earthquakes and minor strike-slip earthquakes in the Eastern Bransfield Basin suggest 1) ongoing extension, and 2) transtensional stress transmitted from the Antarctic–Scotia transform boundaries, the South Scotia Ridge and the Shackleton Fracture Zone. A lack of seismicity in the Central Bransfield Basin supports that active seismicity in the Eastern Bransfield Basin is not a result of subduction along the South Shetland Trench. Shallow focused earthquakes have been observed along the NW–SE trending gravity low line between the Central and the Eastern Bransfield Basins that approximately coincides with the landward projection of a fracture zone in the former Phoenix Plate.

Sedimentary record of explosive silicic volcanism in a Cretaceous deep‐marine conglomerate succession, northern Antarctic Peninsula

Lower Cretaceous conglomeratic strata exposed on southern Sobral Peninsula were deposited on a deep‐marine apron in the back‐arc Larsen Basin close to its faulted boundary with the Antarctic Peninsula magmatic arc. The succession is dominated by amalgamated beds of clast‐supported conglomerate, which, together with minor intercalated sandstones, consist of varied, but largely basaltic to andesitic, volcanic material and clasts derived from the Palaeozoic–Triassic (meta)sedimentary basement of the arc. Most of the volcanic clasts are thought to have been derived from lithified volcanic successions or older synvolcanic deposits, rather than from sites of coeval eruption. These mixed‐provenance strata enclose a number of intervals, consisting mainly of inverse–normally graded conglomerate and graded–stratified pebbly sandstone, in which the sand fraction is dominated by crystals and vitric grains considered to have been redeposited in the immediate aftermath of explosive silicic arc volcanism. Like syneruption deposits on non‐marine volcaniclastic aprons, these intervals are more sand‐prone than the enclosing strata and appear to show evidence of unusually rapid aggradation. Plagioclase from one such interval has yielded 40Ar/39Ar ages concordant at ≈121 Ma, similar to those obtained from the non‐marine Cerro Negro Formation, deposited within the magmatic arc. It is suggested that the two successions can be viewed as counterparts, both recording a history of mainly basaltic to andesitic volcanism, punctuated by relatively infrequent, explosive silicic eruptions. Whereas the Cerro Negro Formation consists mainly of syneruption deposits, most of the volcaniclastic material delivered to the eruption‐distal, deep‐marine apron appears to have been derived by normal degradation processes. Only rare silicic eruptions were capable of supplying pyroclastic material rapidly enough and in sufficient quantities to produce compositionally distinct syneruption intervals.

Deep sea-floor evidence of past ice streams off the Antarctic Peninsula

Research Article| January 01, 2000 Deep sea-floor evidence of past ice streams off the Antarctic Peninsula Miquel Canals; Miquel Canals 1Consolidated Research Group on Marine Geosciences, Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Campus de Pedralbes, E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar Roger Urgeles; Roger Urgeles 1Consolidated Research Group on Marine Geosciences, Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Campus de Pedralbes, E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar Antoni M. Calafat Antoni M. Calafat 1Consolidated Research Group on Marine Geosciences, Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Campus de Pedralbes, E-08028 Barcelona, Spain Search for other works by this author on: GSW Google Scholar Author and Article Information Miquel Canals 1Consolidated Research Group on Marine Geosciences, Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Campus de Pedralbes, E-08028 Barcelona, Spain Roger Urgeles 1Consolidated Research Group on Marine Geosciences, Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Campus de Pedralbes, E-08028 Barcelona, Spain Antoni M. Calafat 1Consolidated Research Group on Marine Geosciences, Department of Stratigraphy and Paleontology, Faculty of Geology, University of Barcelona, Campus de Pedralbes, E-08028 Barcelona, Spain Publisher: Geological Society of America Received: 11 May 1999 Revision Received: 02 Sep 1999 Accepted: 15 Sep 1999 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2000) 28 (1): 31–34. https://doi.org/10.1130/0091-7613(2000)028<0031:DSEOPI>2.0.CO;2 Article history Received: 11 May 1999 Revision Received: 02 Sep 1999 Accepted: 15 Sep 1999 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Miquel Canals, Roger Urgeles, Antoni M. Calafat; Deep sea-floor evidence of past ice streams off the Antarctic Peninsula. Geology 2000;; 28 (1): 31–34. doi: https://doi.org/10.1130/0091-7613(2000)028<0031:DSEOPI>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The past existence of a giant ice stream off the northern end of the Antarctic Peninsula is suggested by a convex-upward, elongated sediment body now at a mean water depth of 1000 m. Because of its morphological characteristics, i.e., a set of parallel to subparallel ridges and grooves to 100 km long, with an overall width of 25 km, we call this depositional body a bundle structure. We hypothesize that bundle structures form by accumulation of basal deformation till under their parent ice streams. From its location, size, and overall characteristics the bundle structure described here constitutes the best preserved, largest, deepest, and relatively low latitude evidence of giant ice streams that flowed offshore Antarctica during glacial maxima. Bundle structures reveal the very dynamic behavior of ice caps in the northern Antarctic Peninsula during the last glacial maximum, with catchment areas draining rapidly under marine-based critical subglacial conditions. Bundle structures represent a new megascale streamlined glacial landform. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Volume of Antarctic Ice at the Last Glacial Maximum, and its impact on global sea level change

The volume of Antarctic ice at the Last Glacial Maximum is a key factor for calculating the past contribution of melting ice sheets to Late Pleistocene global sea level change. At present, there are large uncertainties in our knowledge of the extent and thickness of the formerly expanded Antarctic ice sheets, and in the timing of their release as meltwater into the world’s oceans. This paper reviews the four main approaches to determining former Antarctic ice volume, namely glacial geology, glacio-isostatic studies, glaciological modelling, and ice core analysis and attempts to reconcile these to give a ‘best estimate’ for ice volume. In the Ross Sea there was a major expansion of grounded ice at the Last Glacial Maximum, accounting for 2.3–3.2 m of global sea level. At some time in the Weddell Sea a large grounded ice sheet corresponding to c. 2.7 m of global sea level extended to the shelf break. However, this ice expansion has not yet been confidently dated and may not relate to the Last Glacial Maximum. Around East Antarctica there was thickening and advance offshore of ice in coastal regions. Ice core evidence suggests that the interior of East Antarctica was either close to its present elevation or thinner during the last glacial so the effect of East Antarctica on sea level depends on the net balance between marginal thickening and interior thinning. Suggested East Antarctic contributions vary from a 3–5.5 m lowering to a 0.64 m rise in global sea level. The Antarctic Peninsula ice sheet thickened and extended offshore at the Last Glacial Maximum, with a sea level equivalent contribution of c. 1.7 m. Thus, the Antarctic ice sheets accounted for between 6.1 and 13.1 m of global sea level fall at the Last Glacial Maximum. This is substantially less than has been suggested by most previous studies but the maximum figure matches well with one modelling estimate. The timing of Antarctic deglaciation is not well known. In the Ross Sea, terrestrial evidence suggests deglaciation may have begun at c. 13,000 yr BP 1 1 All dates reported as radiocarbon years before present, unless otherwise stated. but that grounded ice persisted until c. 6,500 yr BP. Marine evidence suggests the western Ross Sea was deglaciated by c. 11,500 yr BP. Deglaciation of the Weddell Sea is poorly constrained. Grounded ice in the northern Antarctic Peninsula had retreated by c. 13,000 yr BP, and further south deglaciation occurred sometime prior to c. 6,000 yr BP. Many parts of coastal East Antarctica apparently escaped glaciation at the LGM, but in those areas that were ice-covered deglaciation was underway by 10,000 yr BP. With existing data, the timing of deglaciation shows no firm relation to northern hemisphere-driven sea level rise. This is probably due partly to lack of Antarctic dating evidence but also to the combined influence of several forcing mechanisms acting during deglaciation.

Lithostratigraphy of Miocene–Recent, alkaline volcanic fields in the Antarctic Peninsula and eastern Ellsworth Land

Miocene–Recent alkaline volcanic rocks form numerous outcrops scattered widely throughout the Antarctic Peninsula and eastern Ellsworth Land. They occur mainly as short-lived (typically 1–2 million years) monogenetic volcanic fields but include a large outcrop area in northern Antarctic Peninsula which includes several substantial polygenetic shield volcanoes that were erupted over a 10 million year period (the James Ross Island Volcanic Group (JRIVG)). As a whole, the outcrops are of considerable importance for our understanding of the kinematic, petrological and palaeoenvironmental evolution of the region during the late Cenozoic. Until now, there has been no formal stratigraphical framework for the volcanism. Knowledge of the polygenetic JRIVG is still relatively poor, whereas a unifying lithostratigraphy is now possible for the monogenetic volcanic fields. For the latter, two new volcanic groups and twelve formations are defined, together with descriptions of the type sections. The volcanic fields (both polygenetic and monogenetic) vary in area from c. 1 to 4500 km2, and aeromagnetic data suggest that one may exceed 7 000 km2. The rocks are divisible into two contrasting petrological ‘series’, comprising basanites–phonotephrites and alkali basalts–tholeiites. The JRIVG is dominated by alkali basalts–tholeiites but also contains rare basanites, and phonotephrite–tephriphonolite compositions occur in minor pegmatitic segregations in sills. By contrast, in the monogenetic volcanic fields, basanites–phonotephrites generally form the older outcrops (mainly 15–5.4 Ma) and alkali basalts–tholeiites the younger outcrops (4(?)–&lt;1 Ma). Throughout the region, erupted volumes of alkali basalts–tholeiites were an order of magnitude greater, at least, than those of basanite–phonotephrite compositions. Interpretation of the lithofacies indicates varied Miocene–Recent palaeoenvironments, including eruption and deposition in a marine setting, and beneath Alpine valley glaciers and ice sheets. Former ice sheets several hundred metres thick, and fluctuating ice surface elevations, which were generally higher during the eruptive periods than at present, can also be demonstrated.

The upper Cenozoic tephra record in the south polar region: a review

Tephrochronology studies in the south polar region are reviewed and evaluated. There have been numerous investigations of tephra layers in ice cores, reflecting the continuing importance of ice cores as a principal source of palaeoenvironmental information. By contrast, tephra in marine sediment cores have been largely neglected. Chemical analyses of glass shards are not uniformly available across the region. In particular, they are currently unavailable for the northern Antarctic Peninsula. Few tephras have been dated directly, although potassic glass and minerals are commonly present and should be readily amenable to isotopic dating. Chemical ‘fingerprinting’ seems to have a high potential for successfully correlating layers and identifying source areas, but only a few studies have considered trace elements as well as major oxides. The effects of within-ash compositional variations and analytical imprecision limit the general utility of ‘fingerprinting’. The tephra record is locally much more complete than is preserved in the source volcanoes themselves. However, the effects of frequent eruptions on local depocentres may swamp other environmentally significant indicators and make the environmental record harder to interpret than in tephra-free successions. Linked studies of tephra and volcanically-derived aerosols in ice in the south polar region could be of critical importance for quantitative calculations of the volcanic contribution to atmospheric fluxes and attempts to assess the possible effects of volcanism on global climate.

High latitude Eocene climate deterioration: evidence from the northern Antarctic Peninsula

Clay mineral, sedimentological and geochemical data show that the northern Antarctic Peninsula (Seymour Island, La Meseta Formation) experienced a climatic deterioration from very warm, non-seasonally wet conditions at the end of the Palaeogene global optimum (early Middle Eocene ∼47 Ma) to a latest Eocene (post ∼34 Ma) regime that was cold, frost-prone and relatively dry. During the middle Middle Eocene there was an episode of strongly seasonal wet conditions, after which the climate was generally cool and humid. Overall, Eocene climatic trends in the Antarctic Peninsula mirror those recorded at ODP sites in the Southern Ocean. There is no evidence for glacial deposition on Seymour Island during either the latest Eocene (Submeseta) or the short Early Palaeocene (Sobral) cold episodes. Local Eocene climatic changes were registered by alterations in depositional and sedimentary characters of the La Meseta Formation, and reflect regional southern high latitude Palaeogene climatic mileu modulated by local tectonic events.

A reassessment of the age of the Cockburn Island Formation, northern Antarctic Peninsula, and its palaeoclimatic implications

New constraints on the age of the Cockburn Island Formation, northern Antarctic Peninsula, resulting from whole rock laser-stepped heated 40 Ar– 39 Ar dating of associated basalt and palaeomagnetic re-calibration of the ranges of the formation’s fossil diatom taxa, suggest that interglacial conditions existed around 3 million years ago. The refined age of the deposit supports continent-wide Late Pliocene warming in Antarctica, and makes more likely the occurrence of extensive marine incursions in East Antarctica at that time.

Late Cretaceous–Cenozoic climatic variations of the northern Antarctic Peninsula: new geochemical evidence and review

Aptian to Pliocene time-series of X-ray fluorescence data from the Antarctic Peninsula are used to assess the degree of chemical weathering and maturity of sediments deposited prior, and subsequent to the establishment of glaciation in West Antarctica. A continuous palaeoclimatic signal is inferred from comparing the results with previously published palaeotemperature and palaeobotanical data. Aptian–Cenomanian (warm/cool), and Santonian–Early Paleocene (warm/cold) cycles were followed by the global Late Paleocene–Early Eocene climatic optimum. Subsequent steady decline in temperatures resulted in glacial conditions in the northern Antarctic Peninsula by Early Oligocene time. Under alternating Cenozoic frigid/cold climates and in sedimentary regimes dominated by physical weathering, geochemical signatures were primarily indicative of provenance. The development of Cretaceous arboreal vegetation in the northern Antarctic Peninsula can be correlated with the major climatic cycles.

The Cockburn Island Formation; Late Pliocene interglacial sedimentation in the James Ross Basin, northern Antarctic Peninsula

The longest-known pectinid-bearing deposit in the Antarctic, the Pecten-conglomerate of Cockburn Island in the James Ross Island group, northern Antarctic Peninsula, is herein formally named the Cockburn Island Formation. A detailed account of its lithology, palaeontology, age and depositional environment is given. Deposition is thought to have taken place during a late Pliocene interglacial episode. The Cockburn Island Formation is younger than 2.8 Ma and is a possible correlative of the Scallop Hill Formation in the McMurdo Sound region, East Antarctica.

Antarctic Peninsular cryosphere: Early Oligocene ( c. 30 Ma) initiation and a revised glacial chronology

Strontium isotope stratigraphy provides a chronology for Cenozoic cryogenic strata in the northern Antarctic Peninsula and allows an assessment of diachronism in onset of glacial conditions between East and West Antarctica. The earliest observed event on the Antarctic Peninsula was late Early Oligocene (29.8 ± 0.6 Ma) (at least c. 4 Ma later than in East Antarctica), with a second in the early Early Miocene (22.6 ± 0.4 Ma). Both glacials and intervening interglacial were continent-wide phenomena. Two late Neogene glaciations are distinguished: early Late Miocene (9.9 ± 0.97 Ma) (Hobbs Glacier/Jones Mountains) and latest Miocene (Alexander Island). A further late Neogene glacial deposit (Weddell Formation) can be constrained only as &lt; c. 10 Ma.

Holocene deglaciation and climate history of the northern Antarctic Peninsula region: a discussion of correlations between the Southern and Northern Hemispheres

The chronology of post-Last Glaciol Maximum deglaciation in the northern Antarctic Peninsula region is discussed. It is concluded that, contrary to what was earlier believed, the deglaciation process here was largely out-of-phase with that in the Northern Hemisphere. Although, for global eustatic reasons, the marine-based glaciers may have retreated simultaneously with ice-melting in the Northern Hemisphere, the land-based glaciers retreated only slowly during the first halfoftlie Holocene, about 9000-5000 BP. This may have been due either to increased precipitation counterweighing ablation or to delayed warming. A distinct but rather brief Glaciol readvancc took place around 5000 BP, probably caused by a period of renewed cooling. It was followed by the Holocene climatic optimum, about 4000-3000 BP. This warm “hypsithermal” period thus came much later than its equivalent in the Northern Hemisphere, but it roughly coincided with the Milankovitchcan Holocene insolation maximum for these southern latitudes.

Seismic facies changes along a nearly continuous 24° latitudinal transect: the fjords of Chile and the northern Antarctic Peninsula

High-resolution seismic reflection profiles and piston cores from bays, fjords, and straits of the inland passage of Chile and the northern Antarctic Peninsula region were used to examine changes in seismic facies along a nearly continuous 24 ° latitudinal transect that encompasses temperate, subpolar, and polar climatic regimes. These climatic regimes are characterized by differences in seismic facies. Eight seismic facies are recognized on the basis of reflection character, intensity of acoustic contrast at bounding surfaces, and external shape of the unit. The northern and central Chilean fjord region is a temperate maritime setting characterized by thick ice-proximal and ice-distal glacial-marine strata and a variety of morainal features. The southern inland passage and the South Shetland Islands of Antarctica represent transitional (sub-polar) glacial-marine settings. These areas are characterized by relict ice-proximal glacialmarine facies and relatively thin ice-distal glacial-marine facies. Morainal ridges occur in bays and fjords of Chile. The northern Antarctic Peninsula is a polar climatic setting. The straits, bays, and fjords of the region have been virtually scraped clean of sediments. A thin, draping glacial-marine unit occurs locally in these areas.