Popular reconstructions of late Paleozoic glaciation depict a single massive ice sheet centered over Victoria Land and extending outward over much of Gondwana. This view is untenable, as interpretations presented here indicate that glaciogenic strata in southern Victoria Land were deposited in a glaciomarine setting, and that ice entered the area from at least two different ice centers on opposite sides of the depositional basin. Reports from other areas also reveal that multiple ice sheets, ice caps, and alpine glaciers diachronously waxed and waned across Gondwana during the Carboniferous and Permian. Glaciogenic rocks of the Lower Permian Metschel Tillite contain glaciotectonic structures and glaciogenic deposits that include (1) sheared diamictites, (2) thrust sheets, (3) massive and stratified diamictites, and (4) sheet sandstones. These features formed as subglacial deforming beds, thrust moraines at glacial termini, and as glaciomarine deposits associated with temperate glaciers. A glaciomarine setting, rather than a glaciolacustrine setting, is suggested, owing to the abundance of meltwater plume deposits. A wedge-shaped sandstone body at the base of the overlying Weller Coal Measures was deposited as a grounding-line fan. Results of this study imply deposition in ice-marginal glaciomarine settings from ice radiating out of multiple glacial centers. These findings are significant because multiple glaciers, covering a given area, contain considerably less ice volume than a single massive ice sheet. Therefore, the waxing and waning of multiple ice masses during the late Paleozoic would have influenced global climate and eustatic sea level much differently than would have a single massive Gondwanan ice sheet.

The Lower Permian Mackellar Formation is well exposed in a 10,000 km 2 outcrop belt in the Nimrod, Beardmore, and Shackleton Glacier areas of the Transantarctic Mountains. This formation directly overlies glacial deposits and provides a unique glimpse of high paleolatitude conditions during the last icehouse to greenhouse transition. The unit records deposition in the Mackellar Lake or Inland Sea (MLIS), a fresh-water body at ~80° S paleolatitude that was broadly analogous to Glacial Lake Agassiz and was filled by fine-grained turbidites. Low total organic carbon (TOC) content and predominant vitrinite and inertinite are consistent with a low influx of organic matter from a sparsely vegetated, recently deglaciated terrain. A widespread but low-diversity ichnofauna and variable (although low overall) levels of bioturbation suggest oxic conditions and a bottom fauna restricted to areas of low sedimentation. Integration of sedimentologic, organic geochemical, and paleobiologic information with results of climate models and characteristics of modern lakes enhances reconstruction of parameters that controlled the functioning of the lake as an ecosystem. Regression equations relating mean annual temperature and mean depth of modern lakes to the number of ice-free days applied to the MLIS indicate ice cover from two to five months a year. Estimates of the depth of mixing and depth to the thermocline, based on maximum length, maximum width, and area, suggest a mixing depth of ~50 m and a thermocline of ~20 m. The MLIS probably was stratified during the summer and was dimictic, with overturns occurring after fall cooling and after ice melt; mixing was enhanced by turbidity currents. Productivity was low, as recorded by the low TOC, but organic matter fixed in the surface water of the lake may have been degraded and not recorded in the sediments. In spite of its high paleolatitude, the MLIS as reconstructed was dynamic and biologically active; the same probably was true of other Permian postglacial lakes.

No abstract available.

Gondwana, though extant for approximately one-half billion years, is now present as fragments across much of the globe. Following an assembly during the latest Protero zoic into the early Phanerozoic, the megacontinent has gradually fragmented to its current dispersed pattern. Paleozoic fragmentation, primarily on its north and west margins, formed a series of ribbon-shaped continents that collided with southern Laurasia and generated major orogenic events. Meanwhile, much of its southern and eastern margin was the site of subduction and associated Cordilleran-style tectonics. Mesozoic and Paleogene rifting completed the fragmentation, sending continents northward to generate the Alpine-Himalayan mountain chain from Spain to China. Much of Gondwana flirted with the South Pole throughout the Paleozoic, and several major glacial episodes resulted. The largest and most extensive of these was the late Paleozoic ice age; the consequences of this event dominated global geology for nearly 100 m.y. and orchestrated the greatest cyclic stratigraphic record in Phanerozoic history.

Widely distributed glacially derived material indicates that an extensive ice sheet covered Western Australia from at least the Gzhelian to mid-Sakmarian times. The earliest glacial sequences may be Bashkirian in the subsurface of the Southern Carnarvon and Canning Basins, although definitive glacial characteristics are less well defined. The younger glacially influenced successions are present in nearly all Phanerozoic basins in Western Australia, and typically comprise a lowermost glacial facies, middle marine mudstone facies, and uppermost fluvial–deltaic strata. Current palynological correlation show that the tripartite successions may not be coeval among all basins, which appears to contradict models of Gondwana-wide glaciation in which the end of glacial conditions is an inter-regional coeval event. However, detailed analysis is hampered by the existing low-resolution biostratigraphic scheme. There is some evidence that subsidence or penecontemporaneous faulting may have locally dominated relative sea-level change and modified regional glacial influences. A dramatic improvement in biostratigraphic resolution is required to resolve the controls on facies distribution, especially to differentiate between deglaciation patterns and periodic ice-sheet advance and retreat, and regional climatic changes and latitudinal differences within Gondwana.

Stratigraphic and sedimentological data from New South Wales and Queensland, eastern Australia, indicate that the late Paleozoic ice age consisted of at least eight discrete glacial intervals (each 1–8 m.y. in duration) separated by nonglacial intervals of comparable duration. These events spanned an interval from the mid-Carboniferous (ca. 327 Ma) to the early Late Permian (ca. 260 Ma), and they illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the Early Permian, followed by an opposite trend toward the final demise of glaciation in the Late Permian. Glacial facies are composed of diamictites, interbedded diamictites, conglomerates and sandstones, rhythmites, laminated mudrocks with dispersed outsize gravel, glendonites, clastic intrusions, faceted, striated, and bullet-shaped clasts, and rare, well-sorted siltstones interpreted as windblown loessites. Carboniferous glacial intervals are predominantly of continental origin and were deposited in an array of mainly glaciofluvial and glaciolacustrine environments. Permian glacial facies, by contrast, were formed mainly in glaciomarine environments. Cyclical vertical stacking patterns occur on a variety of scales, suggesting glacial-interglacial and longer-term fluctuations in climatic conditions.

In Antarctica, late Paleozoic glacigenic strata occur throughout the Transantarctic, Ellsworth, and Pensacola Mountains and in the Shackleton and Heimefront Ranges. The most laterally and stratigraphic continuous exposures occur in the central Transantarctic and Darwin Mountains. These strata were deposited within two topographically expressed basins. The larger of the two basins was a trough-shaped basin that extended between the present locations of the Darwin and Amundsen Glaciers. Basement highs surrounded the basins and formed uplands onto which preglacial, glacial, and postglacial strata onlapped. An examination of late Paleozoic glacigenic units in the Darwin Mountains and the central Transantarctic Mountains reveals that Permian glacio marine sediments were deposited within the basins, and that subglacial diamictites and proximal glaciomarine sediments were deposited along basin margins. This is in marked contrast to earlier reports that identified glacigenic strata in the Transantarctic Mountains as the deposits of a terrestrial glacial system. On some highs, the occurrence of paleosols overlain by postglacial strata suggests that ice-free areas occurred locally along basin margins. A correlation of fossil spores and pollen with Australian palynomorph zones suggests that the Antarctic glacigenic strata are restricted to the Lower Permian. These findings suggest that glaciation was less widespread (temporally and spatially) than previously hypothesized. It is thus unlikely that a single, massive ice sheet covered Antarctica continuously at any time during the Carboniferous and Permian.

Pennsylvanian and Permian glacigenic deposits of the Dwyka Group occur within Karoo basins throughout southern Africa. The largest, the main Karoo Basin, evolved into a foreland basin during Dwyka accumulation. Tectonism along the convergent margin of Gondwana resulted in the formation of a foreland basin bounded by southern (Cape fold belt) and northern (Cargonian Highlands) uplands. Glaciers carved deep paleovalleys into the northern highlands that were later filled by glacigenic and post-glacial strata. Within this basin, a platform facies association composed of four deglaciation sequences occurs. These sequences, which are hundreds of meters thick, consist of thick, massive, basal diamictite lithofacies that grade upward into stratified lithofacies (stratified diamictites, dropstone-bearing mudrocks, and rhythmites). Interpretations depict grounded ice advancing into the basin followed by gradual retreat of the ice front resulting in ice-proximal followed by ice-distal glaciomarine sedimentation. Sensitive high-resolution ion microprobe (SHRIMP) dates of juvenile zircons obtained from tuff beds indicate that the deglaciation cycles were 3.6–8.2 m.y. in duration. Such cycles were likely the result of tectonic development of the foreland basin. Paleocurrent and provenance studies indicate that Dwyka glaciation asynchronously emanated from multiple glacial centers in upland areas, and in Antarctica. Therefore, southern Africa was not covered by a single ice sheet, but instead, smaller ice sheets, ice caps, and alpine glaciers waxed and waned along basin margins during the late Paleozoic. Despite a long history of study, many questions concerning Dwyka glaciation remain.

The Carboniferous-Permian Dwyka Group in southern Namibia is subdivided into four upward-fining deglaciation sequences, each of which is capped by fine-grained glaciolacustrine or glaciomarine deposits. Both the second and the third deglaciation sequences are associated with mudstone units that are particularly widespread—the Ganigobis Shale Member and the Hardap Shale Member. An abundance of marine macrofossils and ichnofossils and extrabasinally derived fallout tuff horizons characterize these mudstones and provide the basis for an integrated high-resolution biostratigraphic and tephrostratigraphic framework. Juvenile magmatic zircons separated from tuff horizons at the base of the Ganigobis Shale Member (top deglaciation sequence II) yield 206 Pb/ 238 U sensitive high-resolution ion microprobe (SHRIMP) ages of 302.3 ± 2.1, 302.0 ± 3.0 Ma, and 299.5 ± 3.1 Ma, whereas a tuff associated with the upper part of the Hardap Shale Member (top deglaciation sequence III) reveals a SHRIMP age of 297.1 ± 1.8 Ma. Since macrofaunal occurrences reveal the Hardap Shale Member to be a correlative of the Gondwana-wide Eurydesma transgression, this datum is an important age calibration for a well-established global event. Tuff beds sampled next to the boundary between the glacial Dwyka Group and the postglacial Ecca Group yield SHRIMP ages of 290.9 ± 1.7 Ma and 288.5 ± 1.6 Ma, providing an age proxy for the end of the late Paleozoic ice age in southern Africa.

In the early Pennsylvanian, glacial lobes draining from an ice sheet probably centered on the northern highlands of Namibia (Windhoek ice sheet) reached the eastern margin of the marine-flooded Paraná Basin in southeastern and southern Brazil. Here, the glacier lobes extended at least 50 km across the depositional surface and terminated in a grounded tidewater system. The late Paleozoic paleolatitude of 40°–50°S of the Paraná Basin is consistent with a temperate warm-based regime for the glaciers. Accumulation of glacially influenced sediments in the main northern depocenter of the rapidly subsiding cratonic depression may have been preceded by deposition of proglacial sandy deposits (Lagoa Azul Formation; terrestrial?). Glacier displacement seems to have been controlled mainly by glacial-estuarine or attenuated fjord-like coastal inlets. The glacial lobes initially moved over highly eroded Precambrian to early Paleozoic crystalline rocks, then middle Paleozoic sedimentary rocks, and eventually over their own deposits. Multiple advance-retreat phases left a carpet of subglacial and meltwater deposits both on land and along the basin margin, although the former deposits have been almost completely eroded away. Continued, albeit less intense, tectonic subsidence of the basin led to southward displacement of the depocenter and more widespread sediment deposition. An ice cap centered on the Rio Grande do Sul shield was drained by lobes that flowed along radially distributed preglacial valleys. On the western basin margin, reduced numbers of lobes not connected to a recognizable major ice mass (or masses) seem to have moved toward the southeast. Destabilized glacigenic debris (mainly sand, diamicton, and mud) accumulated proglacially on the basin ramp and moved downslope by mass-flow processes, resulting in thick and laterally extensive packages of sand and diamicton interbedded with laminites and shales (Lagoa Azul, Campo Mourão, and Taciba Formations). Ubiquitous dropstones in laminites and in massive silty-clayey diamictons point to deposition by rain-out from sediment plumes and icebergs. Repetitive sedimentary cycles consisting of alternations between limited terrestrial facies and intraformational evidence of subglacial processes indicate that glacial conditions in the Paraná Basin persisted for 17–27 m.y. Glacial deposits are overlain by shallow-marine deltaic, coal-bearing sandstone of the Rio Bonito Formation and equivalent beds.

The Bashkirian to Sakmarian-Artinskian Itararé subgroup provides a record of the evolution of the Permian-Carboniferous glaciation in the Paraná Basin (Brazil). The glaciogenic succession was deposited under the influence of glaciers incoming from southwestern Africa. This paper presents an overview of the third-order sequence stratigraphy of that succession and a biostratigraphic summary, showing that: (1) the most complete and thick outcrop portion of the glaciogenic succession occurs in the northeastern part of the Paraná Basin, where several (at least nine) major cycles of ice advance and retreat can be recognized during the development of the Itararé subgroup; (2) biostratigraphically, two well-defined stratigraphic gaps within the Permian-Carboniferous succession are recognized, one within the Itararé subgroup, related to the Lapa–Vila Velha incised valley fill, and another at the Itararé–Rio Bonito boundary, both of which represent regional sequence boundaries; and (3) the transition between palynozones Crucisaccites monoletus and Vittatina costabilis is associated with the maximum flooding surface represented by the marine Lontras Shale, a regional marker bed located in the upper third of the glaciogenic succession.

Glacigenic strata associated with the proto-Precordillera were deposited in the Calingasta-Uspallata and Río Blanco back-arc basins and the Paganzo foreland basin in west-central Argentina during the early Pennsylvanian (upper Namurian; Bashkirian). These basins were formed due to tectonic loading and later postcollisional extension in a convergent-margin setting along the western margin of Gondwana during the Chañic and Río Blanco tectonic events. Uplift of the proto-Precordillera fold-and-thrust belt during the latest Visean–earliest Namurian (Serpukhovian) resulted in the development of a widespread unconformity that formed the pre glacial basin floors. During the Namurian, alpine glaciers carved deep valleys into the upland, and ice drained radially away from the proto-Precordillera. Valley glaciers or an ice cap also occupied basement uplifts in the Sierras Pampeanas to the east. Ice was grounded below sea level in the Calingasta-Uspallata and Río Blanco Basins, where thick glaciomarine successions were deposited. In the Paganzo Basin, a thin glacial succession was deposited in both terrestrial and glaciomarine settings. Throughout the proto-Precordilleran region, deposition is interpreted to have occurred (1) subglacially, (2) in morainal banks, (3) as a result of settling from suspension out of meltwater plumes, (4) as rain-out from melting icebergs, and/or (5) from mass movement and sediment gravity flows. An abrupt upward transition from diamictites to marl-bearing, dropstone-free mudrocks marks glacial retreat and establishment of sediment-starved marine conditions. Above this, coarsening-upward successions and truncation surfaces signal either postglacial deltaic progradation during a forced regression or fluvial incision associated with a base-level fall. Although much is known about these strata, many questions remain, including the age of the deposits, environments of deposition, and the mechanisms responsible for the observed stratigraphic architecture.

Western Gondwana underwent a steady drift from mid-latitudes (~50°S, Early Carboniferous) to lower latitudes (<40°S) by Late Carboniferous time, and glacial deposition had ended in Bolivia by the early Pennsylvanian (Morrowan). At this time, carbonates and evaporites were being deposited across the Perú-Bolivia Basin. The Pennsylvanian and Permian Titicaca Group represents an Andean transgressive marine to restricted carbonate and regressive red bed megasequence (Cuevo Super-sequence or Subandean Cycle). The transgressive part of this Pangean first-order sequence records inherited basement controls and ephemeral pericratonic seaways into the interior of a western landmass. The well-dated Copacabana Formation records many high-frequency sequences and meter-scale cycles that form larger, third- and second-order composite sequences in the central Andes. Diverse carbonates, compositionally immature but texturally more mature arkosic and lithic sandstones, shales, tuffs, and evaporites characterize Copacabana Formation lithologies, which have been dated using foraminifera, fusulinids, conodonts, and palynomorphs. Estuarine barrier sands and cross-bedded, fossiliferous marine sandstones with limestone lithoclasts were derived by reworking of semilithified Copacabana rocks during lowstands and transgressive flooding events. Sedimentation rates in Bolivia were relatively low (7–25 m/m.y.) compared with the thicker and shale-rich Copacabana Formation in Perú. Stacked transgressive systems tracts and highstand systems tracts with significant hiatuses formed in open-marine and restricted to semiarid coastal depositional systems. Twelve second- and third-order, 30–100 m composite sequences have incisement or protosol development above marine limestone of the underlying sequence; extensive siliciclastic lowstand and/or transgressive shoreline facies occur above these sequence boundaries. Thick accumulations of progradational carbonate characterize the highstand systems tracts. More distal subtidal ramp sequences (well-developed in the Cochabamba and northern Subandes areas) are shale-cored with fossiliferous packstone-grainstone caps, but they lack evidence of subaerial exposure or disconformity. Small, meter-scale shallowing-upward parasequences and internal autocyclic, icehouse facies mosaics comprise the larger Copacabana composite sequences. Pennsylvanian sequence boundaries (occurring as a result of glacial drawdowns) occurred at ca. 318 Ma, 311 Ma, 309 Ma, 308 Ma, and 306.5 Ma. Permian drawdowns occurred at 299 Ma, 293 Ma, and 283 Ma.

Three glacial episodes are identified in Upper Devonian and Mississippian strata in South America using sedimentologic, stratigraphic, paleontological, borehole, and outcrop data. The first glacial episode is of late Famennian (“Strunian”) age and is interpreted from strata in basins of Brazil, Bolivia, and Peru, where ice sheets and alpine glaciers reached coastal and marine settings. Biostratigraphically, these strata correspond to the Retispora lepidophyta–Indotriradites explanata or LE Zone and the Retispora lepidophyta–Verrucosisporites nitidus (LN) spore zones of Western Europe. The second glacial episode occurred during the late middle to early late Tournaisian and is recorded in the subsurface of the Solimões Basin (Juruá and Jandiatuba subbasins) of northwestern Brazil and possibly in Bolivia and Argentina. The third glacial episode is of late Visean age and is currently identified in basins of Brazil and possibly in the area of the former Acre Basin shelf, but data are poor. In Bolivia and Peru, the Ambo Group also displays glacially influenced sediments as well as strata in central western Argentina. These glacial episodes may also have occurred in Africa, but data are still scarce, and the ages of potentially coeval strata are not well constrained. Indirect evidence of these Paleozoic glacial events in Gondwana is suggested by researchers in Western Europe, Asia, and in the United States on the basis of geochemical, stratigraphic, sedimentologic, paleontologic, and eustatic data.