The stratigraphic succession in the Ellsworth Mountains includes strata from Cambrian to Permian in age. No definite evidence of major unconformities in the Ellsworth succession is known, and it is possible that continuous deposition took place from Cambrian to Permian time. The oldest stratigraphic unit, the Heritage Group, was deposited in Middle to Late Cambrian time. More than half of the 13,000+-m-thick stratigraphic succession of the Ellsworth Mountains was deposited during this time interval. Basic igneous volcanism and tectonic activity occurred in both the source and accumulation areas throughout the deposition of this group. Shallow-marine conditions prevailed during the deposition of the overlying 3,000-m-thick Upper Cambrian to Devonian Crashsite Group. This group indicates a period of tectonic stability that continued through the remainder of Ellsworth Mountains sedimentation. Deposition of the glaciomarine Permo-Carboniferous Whiteout Conglomerate and the Permian Polarstar Formation completed the sedimentary sequence. Major deformation of the Ellsworth Mountains sedimentary succession, the Ellsworth (Gondwanide) Orogeny, took place in Late Permian or early Mesozoic time. The original location of these rocks is unclear, but they probably accumulated near the margin of East Antarctica. With the breakup of Gondwanaland, the Ellsworth Mountains, and their southern neighbors likely comprised a microplate that translated and rotated to its present position sometime in late Mesozoic or early Cenozoic time. The uplift of the mountains may have accompanied these postulated movements. The geomorphic evolution of the Ellsworth Mountains in Cretaceous and Cenozoic time includes the development of an integrated stream valley pattern and, later, valley and continental glaciation, followed by moderate deglaciation.

The Heritage Group is composed of about 7,500 m of sedimentary strata exposed in the Heritage Range of the Ellsworth Mountains, West Antarctica. The Heritage Group is here redefined to include the Minaret Formation as the uppermost unit. New formations within the Heritage Group are formally described; they are, from the bottom upward, the Union Glacier, Hyde Glacier, Drake Icefall, Conglomerate Ridge, Springer Peak, Liberty Hills, and Frazier Ridge Formations. The Kosco Peak Member of the Union Glacier Formation is also formally described. Deposition of the Heritage Group took place in Middle and early Late Cambrian time in a rapidly subsiding basin bordered by carbonate rock and quartzite source areas of moderate relief. Sediment transport directions were dominantly from the present south and west. Thick, volcaniclastic terrestrial strata lie at the exposed base of the group, and these rocks grade upward into deltaic black shale and normal marine sediments. A number of active volcanic centers were present in the Heritage Range during the deposition of upper Heritage Group strata.

The Crashsite Group of the Ellsworth Mountains, a 3,000-m-thick sequence of shallow-water, mostly marine, tan, green, and red quartzose sandstones (quartzites) and argillites, is here subdivided, in ascending order, into the Howard Nunataks Formation (1,630 m), the Mount Liptak Formation 1,070 m), and the Mount Wyatt Earp Formation (300 m). The Mount Wyatt Earp Formation has yielded Devonian fossils. Late Cambrian trilobites occur in the transition beds at the base of the Crashsite Group, and it is probable that the lower parts of the Group include Ordovician and Silurian strata.

The upper Paleozoic Whiteout Conglomerate, situated conformably upon the Crashsite Group and overlain conformably by the Polarstar Formation, may represent the entire period of Gondwanaland glaciation in West Antarctica. The formation, mainly massive diamictites, makes up about 1,000 m of a 13,000-m-thick total stratigraphic column in the Ellsworth Mountains. In the northern Sentinel Range, the Whiteout Conglomerate contains as many as six dark gray to black, thick, massive-bedded diamictites that are separated by recessive layers of laminated to thin-bedded shale, mudstone, and sandstone as thick as 15 m. Clasts greater than 5 mm in diameter compose 3 to 10 percent of most diamictites. Quartzite (66 percent) is the dominant clast type, with granite (17 percent), shale-argillite (8 percent), and carbonate (5 percent) composing most of the remainder. Some clasts are faceted and striated. A truncated Whiteout section of about 250 m in the Meyer Hills to the south contains thinner diamictites with more variable rock types and a stratigraphic sequence punctuated by striated boulder pavements and thin laminated beds of shale, sandstone, and pebble lags. Of the pebbles in the diamictites, 47 to 86 percent are quartzites. Limestone and granite each compose about 20 percent. Conspicuous changes in pebble compositions occur across contacts marked by boulder pavements. Petrographically, the diamictites are 62 percent silt and clay matrix with 38 percent sand grains and granules. The sand-sized grains have an average quartz/feldspar/lithic (Q:F:L:) ratio of 75:9:16; the studied specimens displayed no significant petrographic variations between the northern Sentinel Range and the Meyer Hills. However, there is a difference in megaclast compositions; in the northern Sentinel Range, shale-argillite and vein quartz are abundant, but they are absent in the Meyer Hills where carbonate is abundant. Till pellets, products of ablation on glaciers and icebergs, are common in bedded units and rare in the diamictites. The Crashsite Group quartzite and Whiteout Conglomerate are dominated by quartz and quartz-rich lithic fragments, whereas the overlying Polarstar Formation contains abundant volcanogenic detritus, reflecting a dramatic change in source area. Contact zones with both enclosing formations contain scattered oversized clasts. Striated boulder pavements in the Meyer Hills generally indicate paleo-ice flow to the present northwest. With the Ellsworth block restored to its probable late Paleozoic position via a 90° clockwise rotation, the glacier source area was the East Antarctica landmass now situated south of the Ellsworth Mountains. Sedimentologic similarities with formations in the Pensacola Mountains to the south indicate that the Ellsworth Mountains have moved northward at least 500 km from a hypothetical former position just east of the Pensacolas. Our glacial model suggests that ice sheets generated the glacial sediments of the Whiteout Conglomerate under a polar climatic regime. The Meyer Hills sequence represents deposition directly by glaciers and also by floating ice and currents in a zone of fluctuating grounding line. Deeper water and sub-ice shelf conditions, i.e., glacial-marine, are postulated for the thick sequence of the northern Sentinel Range. There, periodic retreat of the ice shelf margin was accompanied by iceberg rafting and bottom current activity, probably in response to climatic warming.

The Polarstar Formation, a 1-km-thick argillite and sandstone unit, is the uppermost part of a thick Cambrian to Permian sedimentary sequence in the Ellsworth Mountains. The formation gradationally overlies the Whiteout Conglomerate, an Upper Carboniferous-Lower Permian glacial diamictite. The lower part of the Polarstar is mostly argillite, and the middle part consists of coarsening-upward cycles of argillite to sandstone. These cycles begin with lenticular bedding overlain by wavy and flaser bedding and end with ripple-laminated, fine-grained sandstone to cross-bedded, medium-grained sandstone. The upper part of the formation consists of fining-upward cycles of channel-form, cross-bedded, medium-grained sandstone overlain by fine-grained sandstone and of Glossopteris -besaing siltstone, argillite, and coal. The sequence of facies suggests that the depositional environment changed temporally in this area from prodelta to delta and coastal plain. The occurrence of a marginal-marine trace fossil fauna in the middle of the formation and the complete absence of a marine shelly fauna suggest depositional conditions ranging from anaerobic to dysaerobic in a stratified inland sea. Detrital grains in Polarstar sandstone indicate a source terrane dominated by silicic to andesitic volcanic rocks, including tuffs, with minor mafic volcanic and low-grade metamorphic and granitic rocks. The Polarstar Formation was probably deposited in a back-arc basin between the Pacific margin of Gondwanaland and the East Antarctic craton.

Carbonate rocks were studied from the Middle Cambrian Drake Icefall Formation and the Middle to Upper Cambrian Minaret Formation. Additionally, carbonate clasts from the Middle Cambrian Union Glacier Formation and the Permo-Carboniferous Whiteout Conglomerate were examined. No in situ Lower Cambrian carbonate rocks are known to crop out in the Ellsworth Mountains; only reworked clasts of such rocks are found in the Heritage Group and the Whiteout Conglomerate. These clasts suggest that during Early (and Middle?) Cambrian time, a wide carbonate platform developed in or close to the Ellsworth Mountains. This was the site of skeletal algae and archaeocyathid boundstones with sparry calcite or mud as matrix—typical sediments of an open marine environment with low to medium hydrodynamic energy. Oolites are common, and a high-energy environment was required to form these oosparites. These grains, with a diameter between 4 and 7 mm, are made up of concentric ooids with simple and complex structures. Nuclei consist of abraded ooids and oolitic intraclasts. Half-moon ooids with collapsed internal structure are attributed to partial solution, and they indicate a hypersaline depositional environment (aragonite or calcium sulfate?) for some parts of the oolitic bank facies. Laminites with fenestral structures are also present, and they represent low-energy lagoonal deposits. These occur along with dome-shaped and LLH stromatolites that indicate an intertidal environment. Some areas of the carbonate platform were elevated and partly dissolved by fresh water. During the following period of subsidence, voids were filled with fibrous carbonates by rhythmic cementation. Renewed uplift resulted in erosion and destruction of the carbonate platform. The lowest in situ marly and oolitic carbonates are found in the Middle Cambrian strata of the Heritage Group north of Drake Icefall, but these were not extensively studied. The Upper Cambrian Minaret Formation is also autochthonous, and its thickness increases southward from 8 m in the northern Webers Peaks to several hundred meters in the Marble Hills area. Medium to high hydrodynamic energy conditions prevailed during deposition of the Springer Peak section of the Minaret Formation (biosparite, oncosparite, pelsparite). The high diversity of the fauna indicates an open marine environment. The section at Yochelson Ridge starts with a few meters of still-water carbonate rocks that are overlain by high-energy oolitic carbonate rocks and calcarenites. Farther to the south (south of Mount Dolence), facies fluctuate from medium-energy (oncolite) to high-energy (oolite) environments. Fossils (brachiopods and trilobites) are rare. Near the top of the sequence a hypersaline milieu is indicated by layers of early diagenetic dolomicrite. Similar fades are exposed in the Liberty and Marble Hills areas. Fast subsidence in this area was compensated by rapid sedimentation of shallow-water carbonates.

Middle Cambrian or probably Middle Cambrian trilobites were collected at six localities in the Heritage Range of the Ellsworth Mountains, including Yochelson Ridge, Drake Icefall area, Edson Hills, Liberty Hills (two locations), and Marble Hills. The total fauna includes 14 genera (2 new) and 32 species (5 new). Due to original preservation and/or deformation, a number of the forms are not assignable to specific taxa. The new taxa described herein are Peronopsis deons sp. nov., Pagetia edsonensis sp. nov., Sohopleura drakensis gen. et sp. nov., Pseudobergeronites spinosa gen. et sp. nov., and Blountia perplexa sp. nov. The trilobites were found in formations of the upper Heritage Group (Springer Peak Formation, Drake Icefall Formation, and Liberty Hills Formation). The trilobite faunas described show affinities with faunas from northern Victoria Land (Antarctica), Tasmania, Queensland, China, Kazakhstan, and North America. All faunas are probably Middle Cambrian in age (Templetonian and Boomerangian on the Australian biochronological scale).

Late Cambrian (Late Dresbachian; Idamean) trilobite faunas have been recovered from four localities (Inferno Ridge, Yochelson Ridge, Springer Peak, and the Windy Peak-Pipe Peak area) in the Heritage Range of the Ellsworth Mountains, West Antarctica. Trilobites are most abundant, best preserved, and most diverse in the Minaret Formation at Springer Peak, where they are associated with monoplacophorans, gastropods, rostroconchs, archaeocyathids, articulate and inarticulate brachiopods, pelmatozoans, conodonts and algae. The Heritage Range material includes taxa with North American, Australian, Chinese, and southern Russian affinities and represents three distinct faunal assemblages. Trilobites from the base of the Minaret Formation at Yochelson Ridge represent the Aphelaspis Zone, and trilobites from the Minaret Formation at Springer Peak represent the Dunderbergia Zone. A single parabolinoidid trilobite species (gen. and sp. indet.) from the Windy Peak-Pipe Peak area may represent the Elvinia Zone. Deformed solenopleuracean trilobites stratigraphically below the other three faunas (gen. and sp. indet.) were recovered from Inferno Ridge. From the four localities 15 genera, 1 new subgenus, and 24 species (8 new) are described. New taxa include Idolagnostus (Obelagnostus) imitor n. subgen., n. sp., Eugonocare? nebulosum n. sp., Changshanocephalus? suspicor n. sp., Bathyholcus? conifrons n. sp., Protemnites magnificans n. sp., Onchopeltis variabilis n. sp., ? O . acis n. sp., and O.? neutra n. sp.

Cambrian rocks of the Springer Peak and Minaret formations of the upper Heritage Group contain conodont faunas. The upper Middle Cambrian Springer Peak Formation has yielded a conodont cluster referable to Phakelodus , and the Upper Cambrian Minaret Formation has yielded conodonts of the genera Furnishina , Proacodus, Phakelodus , and Westergaardodina . Three species each of Furnishina and Westergaardodina are known worldwide; other specimens of Westergaardodina may represent new species, but low numbers and generally poor preservation preclude reliable diagnosis. All of the identified paraconodont and protoconodont taxa are long ranging, but they are consistent with the Cambrian age of the host rocks as determined by the other contained fossils.

Cambrian mollusks are known from four localities in the limestone of the Minaret Formation, Heritage Range, Ellsworth Mountains, West Antarctica. The most diverse and best-preserved specimens are from the coquina at the feather edge of the Minaret Formation, on the northeastern side of Springer Peak, Webers Peaks. This locality has provided one of the finest Upper Cambrian mollusk faunas in the world. The mollusks indicate a Dresbachian to Franconian age. The trilobites associated with the mollusks define the age of the rocks at Springer Peak as late Dresbachian (Idamean). These rocks were first thought to be Precambrian in age. From the four localities, 19 genera (4 new) and 20 species (12 new) are described; there are 7 species of monoplacophorans placed in 7 genera, 6 species of gastropods placed in 6 genera, 3 species of hyoliths placed in 3 genera, and 3 species of rostroconchs placed in 3 genera. One calcareous tubular organism is described under the hyoliths as Orthothecida? species indeterminate. The higher taxa are presented in the order of decreasing abundance of specimens in the coquina at Springer Peak. Mollusks make up about 5 percent of the coquina, which at this locality is as much as 8 m thick. The remainder of the coquina is almost entirely trilobite fragments; minor elements of the biota are archaeocyaths, inarticulate and articulate brachiopods, echinoderm fragments, conodonts, and algae. The fossiliferous beds at Springer Peak are interpreted as having been deposited in a medium- to high-energy, nearshore environment under normal marine conditions. The less fossiliferous limestone beds above and below the coquina are laminated, and some contain pisoliths; this evidence of algal activity suggests a low-energy environment. Some of the Upper Cambrian species of mollusks found at Springer Peak occur farther south in the Minaret Formation limestones at Bingham Peak and Yochelson Ridge. One species of helcionellacean mollusk, not found elsewhere, was recovered from the Minaret Formation at its type locality in the Marble Hills. This species is classified as Latouchella ? species indeterminate; it shows that the Minaret Formation is Cambrian in age throughout its thickness and outcrop area. Various of the genera of mollusks known from the Minaret Formation, as well as one species, are geographically widespread in rocks of Late Cambrian age in Australia, northeastern China, and the upper Mississippi River Valley and Ozark Dome regions of the United States. Geographic distributions are discussed under each taxon. The new taxa of mollusks are: (1) monoplacophorans— Cosminoconella runnegari n. gen., n. sp.; Ellsworthoconus andersoni n. gen., n. sp.; Kirengella pyramidalis n. sp.; Proconus incertis n. gen., n. sp.; and Proplina rutfordi n. sp.; (2) gastropods— Aremellia batteni n. gen., n. sp.; Euomphalopsis splettstoesseri n. sp.; Kobayashiella ? heritagensis n. sp.; “Maclurites” thomsoni n. sp.; and Matherella antarctica n. sp.; (3) hyoliths— Linevitus ? springerensis n. sp.; and (4) rostroconchs— Apoptopegma craddocki n. sp.

A diverse Late Cambrian fossil fauna was recovered from the Minaret Formation, Springer Peak, Heritage Range, Ellsworth Mountains, West Antarctica. Fossils include trilobites, molluscs, conodonts, brachiopods, archaeocyathids, and Pelmatozoa. The articulate and inarticulate brachiopods, archaeocyathids, and Pelmatozoa are described here; the remainder of the fauna is described elsewhere in this volume. In articulate brachiopods make up a small percentage of the Springer Peak fauna but are abundant enough to be present in most hand specimens. Preservation is poor. Genera present include Dactylotreta , Lingulella , Micromitra , Quadrisonia , Schixambon , Treptotreta , Zhanatella , and Angulotreta , which is represented by a new species A. ellsworthensis . The assemblage has affinities with those of Australia, suggesting an early Late Cambrian (upper Idamean) age. Articulate brachiopods are rare in the Springer Peak fauna, and a single species resembling Billingsella borukaevi is present. Archaeocyathids make up a small percentage of the fauna but are abundant on some bedding surfaces. They are represented by a single species referred to Antarcticocyathus webersi . Pelmatozoa are rare, but abundant columnals, probably representing eocrinoids, are present on some bedding surfaces.

An Early Devonian orbiculoid brachiopod fauna was reported by Boucot and others (1967) from the Crashsite Quartzite of the northern Heritage Range of the Ellsworth Mountains. Re-collection on this site from strata now known as Mt. Wyatt Earp Formation of the Crashsite Group (Spörli, this volume) has yielded a diverse but sparse and poorly preserved fauna dominated by orbiculoid brachiopods ( Orbiculoidea cf. falklandensis Rowell). Also present in the fauna are cephalopods (identifiable only to the order Orthocerida), pelecypods ( Nuculites aff. N. cuneiformis Conrad; and Grammysiodea? sp. indt.), a rostroconch ( Hippocardia? sp. indt.), gastropods ( Holopea? sp. indt.), a fish spine ( Machaeracanthus cf. kayseri Kegel), and single unidentifiable specimens of a conularid, a trilobite, and an articulate brachiopod. The fauna correlates with those of the Lower Devonian Horlick Formation, Ohio Range, Horlick Mountains, Antarctica, and with those of the Lower Devonian of the Falkland Islands and represents the Malvinokaffric Faunal Province.

A small collection of limestone clasts from the Whiteout Conglomerate (Permo-Carboniferous), Ellsworth Mountains, was examined for archaeocyathids and other fossils. Thirty or more poorly preserved archaeocyathid specimens are here referred to Ajacicyathus sp., Gordonicyathus sp., Erismacoscinus cf. endutus , ? Graphoscyphia sp., and Paranacyathus cf. parvus , ? Dictyocyathus quadruplex , and Archaeocyathus sp. Other fossils observed but not described include fragmentary specimens of sponge spicules, Chancelloria rosettes, trilobites, and brachiopods. The limestone clasts were derived from a source area with exposed Lower Cambrian strata.

Plant megafossils are described and illustrated from several localities and stratigraphic levels within the Ellsworth Mountains. The flora is dominated by various species of Glossopteris foliage and also includes sphenophyte stems and leaf sheaths, glossopterid reproductive organs, Gangamopteris leaves, and Vertebraria -type axes. The plants are preserved as impressions in fine-grained shale within the Polarstar Formation. Based on comparisons with other Antarctic and Gondwana floras, a Middle to Late Permian age is suggested.

Igneous rocks exposed in the southern Heritage Range include two diabasic sills (100 m and 300 m thick), three gabbroic stocks (outcrop areas each <0.5 km 2 ), a spessartite lamprophyre plug (200 m diameter), a 10-km 2 sanidine quartz phytic dacite stock, and numerous aphanitic to porphyritic dikes and lava flows. Lava flows that are largely basaltic, but range in composition from basalt to alkali rhyolite, compose about 10 to 15 percent of the 1,000-m thickness of the Liberty Hills Formation of the Heritage Group. Eighty-four samples have been analyzed for major, minor, and trace elements by x-ray fluorescence. Field relations and comparison of chemical composition of intrusive and extrusive rocks suggest that all igneous rocks in the southern Heritage Range except the dacite stock were emplaced in Cambrian time; all have undergone pumpellyite-actinolite or greenschist facies metamorphism. A four-point Rb-Sr isochron yields a mid-Devonian (369 ± 18 Ma) emplacement age for the dacite stock. The extrusive igneous rock suite is dominated by basalts but also includes rhyolites, dacites, and sparse andesites and is thus bimodal. The relict primary mineralogy, distribution of alteration-resistant trace elements (Nb, Ti, Y, Zr), and incorporation within a thick sequence of carbonate and clastic sedimentary rocks all suggest that the mafic igneous rocks are continental basalts whose original chemical compositions were largely mildly tholeiitic or transitional between tholeiitic and alkali basalt; some calc-alkaline traits are also evident. Discrimination diagrams based on alteration-resistant trace elements and distribution of large ion lithophile elements (Ba, Rb, Sr) suggest that the felsic and intermediate rocks also possess tholeiitic, calc-alkaline, and alkaline traits. Age relations and comparison of chemical compositions indicate that the southern Heritage Range igneous rocks are not correlative with either the Jurassic Ferrar Super-group or the Jurassic Kirwan Volcanics of the Transantarctic Mountains. The most likely possible correlatives might be diabasic sills and dikes and subordinate plugs and sills of felsic porphyry intrusive into the upper Precambrian Patuxent Formation, which crops out in the Neptune Range of the Pensacola Mountains 500 km to the southeast. Tholeiitic suites with contemporaneous calc-alkaline and alkaline traits are unusual but have been reported from the Yellowknife volcanic belt in Canada’s Northwest Territories and from southeastern Maine. We conclude that the bimodal basaltic-rhyolitic suite of igneous rocks from the southern Heritage Range was emplaced in a continental area undergoing extensional tectonism and does not represent an island arc-continental margin subduction zone complex.

Airborne gamma-ray spectrometry can be used as a remote sensing technique to measure the radioelement distribution in the sedimentary sequence that crops out in the Ellsworth Mountains. By means of a highly sensitive detector system it is possible to obtain an almost instantaneous chemical analysis for equivalent uranium, thorium, and potassium that is updated in flight each second. Data provided by this technique, together with visual information recorded during flights, can serve as a reliable basis for stratigraphic correlation and can furnish additional information on diagenetic and sedimentological factors. The radiometric signature of each of the outcropping sedimentary units was determined, and this signature was found to vary within clearly defined limits. The study revealed no significant radiometric anomalies in the Ellsworth Mountains, and this implies that the low-grade metamorphism that is widespread in the area was not sufficient to cause substantial alteration of the original radioelement distribution in the sedimentary rocks.

The Middle to Upper Cambrian Heritage Group, exposed in the Heritage Range of the Ellsworth Mountains, contains interlayered basaltic lava flows and intrusive gabbroic stocks, dikes, and sills that preserve evidence of a pretectonic burial metamorphism. Three zones ranging from the upper prehnite-pumpellyite facies (zone I) through the pumpellyite-actinolite facies (zone II) to the greenschist facies (zone III) are correlated with stratigraphic depth of the mafic igneous rocks in the Heritage Group. A temperature of approximately 370°C is obtained for the boundary between the pumpellyite-actinolite facies and the greenschist facies on the basis of Fe/(Fe+Al) in epidote coexisting with pumpellyite + chlorite + actinolite + quartz. A geothermal gradient of approximately 23 to 24°C/km is estimated for the stratigraphic interval containing pumpellyite-actinolite facies assemblages. Syntectonic recrystallization associated with the development of penetrative foliation in the metasedimentary country rocks is only sparsely developed in the prehnite-and/or pumpellyite-bearing mafic igneous rocks, whereas the more penetratively deformed igneous rocks lack evidence of subgreenschist facies conditions. This differential recrystallization may account for the variation in K-Ar whole-rock ages reported previously for the mafic igneous and metasedimentary rocks of the Heritage Group.