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.

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.

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.

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.