Cockburn Island Research Articles

Mosses of Cockburn Island plateau, Antarctica

Abstract Located east of the Antarctic Peninsula, Cockburn Island is a small island in the James Ross Archipelago. Studies of mosses on the island are scarce. The oldest studies date from the first half of the nineteenth century to the most recent in 1993. The number of records of mosses is very small due to the difficulty of accessing the area. Here, we report an updated composition of the moss flora of the plateau, in which four new records have been found: Bryoerythrophyllum antarcticum, Ceratodon purpureus, Pohlia wilsonii and Schistidium lewis-smithii. The occurrence of these species on the plateau shows that the ranges of these species have expanded from the Antarctic Peninsula to the east. This collection highlights the need for further research into the dynamics of moss flora in the context of climate change.

Revision of Southern Hemisphere taxa referred to Fosterella (Crustacea: Cirripedia), and their extinction in response to Pleistocene cooling.

Extensive barnacle coquinas (barnamols) formed around New Zealand's North and Chatham Islands during the late Pliocene to early Pleistocene. The inner-shelf megabalanine Fosterella is the primary constituent of these lithofacies, which also include epifaunal bivalves, bryozoans and less modified balanids like Notobalanus and Notomegabalanus. The status of genus Fosterella is reviewed, 3 species are retained and a new genus, Porobalanus, is proposed for Fosterella hennigi, a species restricted to the Early Pliocene of Cockburn Island, Antarctica. Significantly, Fosterella did not survive the New Zealand Pleistocene, although Notobalanus and Notomegabalanus, which have fossil records extending back to the Early Miocene, remain important components of present day cool-temperate Southern Hemisphere faunas. Extinction of Fosterella, in shelf waters off Argentina, is explained through a combination of changing circulatory and sedimentary regimes, competition for food and space, predation and physiological constraints. The driver of these factors was rapid regional cooling. Zoobank registration: urn:lsid:zoobank.org:pub:DBB1CB34-83E4-48BA-AA10-81823017F37A.

Reworked late Neogene Austrochlamys anderssoni (Mollusca: Bivalvia) from northern James Ross Island, Antarctica

AbstractWe report on the discovery of a new outcrop of fossiliferous Neogene sediments on northern James Ross Island, northern Antarctic Peninsula. Approximately 100 specimens of the pectinid bivalve Austrochlamys anderssoni (Hennig, 1911) were collected from the permafrost active layer. This bivalve species has a late Miocene to late Pliocene range and has previously been reported from both the glaciomarine Hobbs Glacier Formation and the interglacial Cockburn Island Formation in the James Ross Island area. The localized presence of abundant A. anderssoni within the permafrost suggests that the fossils have been frost heaved from an outcrop of either the Cockburn Island or the Hobbs Glacier formations, originally deposited on northern James Ross Island. The overall shell form, general absence of associated Antarctic Peninsula-derived clasts in the host sediment, and the measured 87Sr/86Sr isotope ratio of the shells (0.709050) which is indistinguishable from that for pectinid bivalves from the Cockburn Island Formation on Cockburn Island (0.709047) suggest that the shells were derived from a unit similar in age to the Cockburn Island Formation. This suggests that the Cockburn Island Formation was originally more laterally extensive than was previously known.

Sea ice extent and seasonality for the Early Pliocene northern Weddell Sea

Growth increment analysis coupled with stable isotopic data ( δ 18O/ δ 13C) from Early Pliocene (ca 4.7 Ma) Austrochlamys anderssoni from shallow marine sediments of the Cockburn Island Formation, northern Antarctic Peninsula, suggest these bivalves grew through much of the year, even during the coldest parts of winter recorded in the shells. The high frequency fluctuation in growth increment width of A. anderssoni appears to reflect periodic, but year-round, agitation of the water column enhancing benthic food supply from organic detritus. This suggests that Austrochlamys favoured waters that were largely sea ice free. Our data support interpretation of the Cockburn Island Formation as an interglacial marine deposit and the previous hypothesis that Austrochlamys retreated from the Antarctic as sea ice extent expanded, this transition occurring during climate cooling in the Late Pliocene.

FORAMINIFERA FROM LATE PLIOCENE SEDIMENTS OF HEIDEMANN VALLEY, VESTFOLD HILLS, EAST ANTARCTICA

The foraminiferal fauna in Pliocene (3.5–2.6 Ma) sediments excavated in a trench 4 m deep, in Heidemann Valley, Vestfold Hills, East Antarctica is examined and described. Sediments accumulated in shallow, fully marine conditions in a glacial valley during the last major glacial event in the Vestfold Hills. The section correlates well with the Cockburn Island Formation ( Pecten Conglomerate), sediments of Wright Valley, Dry Valleys, and marine event M10 recognized as far south as Amery Oasis, 500 km to the southwest of Heidemann Valley. The foraminiferal fauna generally is dominated by infaunal cassidulinid and elphidiid species. Assemblages vary dramatically, even between samples collected very close to each other, and no simple relationship with the position in sections or the valley can be determined. It is a shallow-water, fully marine fauna virtually free of agglutinated forms and with a low planktonic component Planoglabratella webbi is described as new.

Relict shoreline features at Cockburn Island, Ontario

Cockburn Island, Ontario (45°55′ N, 83°20′ W), holds at least six sets of elevated lake bluffs, scarps and bar deposits that mark distinctive water planes above the Nipissing Great Lakes water plane (∼198 m). These relict shoreline features occur at elevations that correspond closely with the elevations of others at nearby St. Joseph Island and in eastern upper Michigan. Together, the elevations and relative locations of steep relict bluffs suggest a proto-Cockburn Island once interrupted the surface of proglacial Lake Algonquin. The islet appears to have emerged and grown through a period of uplift and a sequence of lowering water levels. The highest relict shoreline (280.2 m) is correlated with the Main phase of Lake Algonquin. Lower shorelines at Cockburn Island cannot be correlated consistently, so additional work is required.

A revised Pliocene record for marine- 87Sr/ 86Sr used to date an interglacial event recorded in the Cockburn Island Formation, Antarctic Peninsula

We present a revised 87Sr/ 86Sr-curve for marine-Sr in the interval 2.5–4.5 Ma using analysis of Orbulina universa from the Middle Pliocene type section in Sicily (Punta Piccola section) and a mixed assemblage of planktonic foraminifera from ODP Site 758A and B. The new calibration is used, together with new 87Sr/ 86Sr analysis of pectenid calcite from Cockburn Island, Antarctica, to confirm an age of 4.7 Ma for the pectenids of the Cockburn Island Formation (formerly the Pecten Conglomerate), a unit important in marking a period of warmth and possible glacial retreat in Antarctica. Finally, to aid interlaboratory comparison of 87Sr/ 86Sr data, we calibrate a value of 0.709174 for EN-1 against a value of NIST 987 of 0.709248.

Austrochlamys heardensis (Fleming, 1957) (Bivalvia: Pectinidae) from Central Kerguelen Plateau, Indian Ocean: palaeontology and possible tectonic significance

Austrochlamys heardensis (Fleming) is recorded from a boulder of Late Pliocene (3.62–2.5 Ma) volcaniclastic sandstone dredged 70 km east-north-east of Heard Island, the third record of the species. The collection is much larger than the original described by Fleming and includes left valves which are described for the first time. The species is compared with A. anderssoni (Hennig) from Cockburn Island and ‘Chlamys’ mawsoni Fletcher from Îles Kerguelen. The source rock accumulated in fully marine, highly current-affected conditions. The collection is dominated by right valves, possibly because left valves are more susceptible to breakage and the effects of current winnowing. The locality may have subsided some 500 m since deposition. It lies immediately north of a straight, north-east–south-west trending lineament which may mark a major tectonic feature with left-lateral displacement of approximately 50 km, and provides a natural boundary within the Central Province of Kerguelen Plateau.

Age and environment of Miocene–Pliocene glaciomarine deposits, James Ross Island, Antarctica

Knowledge of the late Miocene–Pliocene climate of West Antarctica, recorded by sedimentary units within the James Ross Island Volcanic Group, is still fragmentary. Late Miocene glaciomarine deposits at the base of the group in eastern James Ross Island (Hobbs Glacier Formation) and Late Pliocene (3 Ma) interglacial strata at its local top on Cockburn Island (Cockburn Island Formation) have been studied extensively, but other Neogene sedimentary rocks on James Ross Island have thus far not been considered in great detail. Here, we document two further occurrences of glaciomarine strata, included in an expanded Hobbs Glacier Formation, which demonstrate the stratigraphic complexity of the James Ross Island Volcanic Group: reworked diamictites intercalated within the volcanic sequence at Fiordo Belen, northern James Ross Island, are dated by 40Ar/39Ar and 87Sr/86Sr at c. 7 Ma (Late Miocene), but massive diamictites which underlie volcanic rocks near Cape Gage, on eastern James Ross Island, yielded an Ar–Ar age of < 3.1 Ma (Late Pliocene). These age assignments are confirmed by benthic foraminiferal index species of the genus Ammoelphidiella. The geological setting and Cassidulina -dominated foraminiferal biofacies of the rocks at Fiordo Belen suggest deposition in water depths of 150–200 m. The periglacial deposits and waterlain tills at Cape Gage were deposited at shallower depths (< 100 m), as indicated by an abundance of the pectinid bivalve ‘Zygochlamys’ anderssoni and the epibiotic foram Cibicides lobatulus. Macrofaunal and foraminiferal biofacies of glaciomarine and interglacial deposits share many similarities, which suggests that temperature is not the dominant factor in the distribution of late Neogene Antarctic biota. Approximately 10 m.y. of Miocene–Pliocene climatic record is preserved within the rock sequence of the James Ross Island Volcanic Group. Prevailing glacial conditions were punctuated by interglacial conditions around 3 Ma.

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.

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.

Oligocene and Pliocene interglacial events in the Antarctic Peninsula dated using strontium isotope stratigraphy

Strontium isotope stratigraphy is used to date two interglacial-marine deposits in the Antarctic Peninsula region. On King George Island, interglacial pectinid-rich sediments in the Low Head Member of the Polonez Cove Formation give a strontium isotope stratigraphy age of 29.0 +0.7 −0.6 to 29.8 +0.8 −0.7 Ma (mid-Oligocene), which, in conjunction with previous K–Ar dating of volcanic rocks, indicates a glacial episode in the Antarctic Peninsula between middle Eocene (42.0 ±1.0 Ma) and mid-Oligocene time. In addition, an inter-glacial deposit (Pecten Conglomerate) from tectonically-elevated exposures on Cockburn Island is dated as Pliocene (3.5–5.3 Ma). Published data suggest these latter sediments were deposited under shallow marine conditions, which were warmer than those of present-day Antarctica.

Angular unconformity between the López de Bertodano and La Meseta formations (Campanian-Maastrichtian and Eocene), Cockburn Island, northern Antarctic Peninsula

A thick, largely shallow marine succession of Cretaceous and Lower Tertiary strata, deposited in the James Ross Basin, is well exposed on an archipelago of islands at the northern end of the Antarctic Peninsula. This succession was thought to be relatively continuous, particularly on Seymour Island where a thick Upper Cretaceous succession passes up into Paleocene and Eocene strata. Several unconformities present in the succession were thought to be relatively minor and have been ascribed to sea level changes. Equivalent sedimentary deposits of the López de Bertodano and La Meseta formations, Campanian/Maastrichtian and Lower Eocene respectively, are exposed on Cockburn Island, less than 10 km from Seymour Island. The contact between the two units is an unconformity with an angular discordance varying from 20° to 55°. Rotation of the López de Bertodano Formation corresponds with syn-sedimentary disruption elsewhere in the basin throughout the Late Cretaceous and points to persistent instability. The ages of the strata on either side of the uncorformity have been dated on the palynological content of five samples and correlation with the Seymour Island succession suggests that at least 900 m of Cretaceous (650 m) and Lower Tertiary (250 m) strata are missing from, or were not deposited at, Cockburn Island. Reworked Maastrichtian palynomorphs in a breccia bed within the La Meseta Formation confirm that Upper Cretaceous strata were eroded although there is no evidence for reworking of Paleocene sediments. We conclude that Cockburn Island includes a continuation of the Eocene unconformity of Seymour Island, extending the trend for the base of the La Meseta Formation to onlap onto progressively older strata. This unconformity may mark a major phase of basin inversion, with tilting and uplift possibly affecting much of the James Ross Basin at this time.

The vegetation of Cockburn Island, Antarctica

Cockburn Island, off the north-east Antarctic Peninsula, is important in the history of Antarctic terrestrial biology as it was here where the first botanical collections were made by JD Hooker in 1843. These, and a subsequent collection made by IM Lamb one hundred years later, are described here. A much more detailed survey of the vegetation of the island was made in 1989. At least nine moss, 34 lichen, three cyanobacteria and one alga taxa were recorded, and the floristic composition of several distinct communities assessed. The floristically most interesting and diverse sites are on the island's 250 m high plateau which possesses seepage areas and welldeveloped networks of polygons and stone circles. The vegetation is similar to that occurring on the mainly sedimentary deposits and rocks of nearby James Ross and Seymour Islands, but significantly different to that on the more acidic soils and rocks which predominate throughout much of the maritime Antarctic.

Stratigraphy and paleontology of Campanian and Eocene sediments, Cockburn Island, Antarctic Peninsula

Approximately 150 meters of fine-grained Campanian sediments and over 100 meters of fine- to medium-grained Eocene sands underlie Pliocene basalts and conglomerates on Cockburn Island, northeastern Antarctic Peninsula. The Campanian beds are part of the “Unnamed strata” of the Marambio Group and contain invertebrate and palynomorph fossils that predate the adjacent Seymour Island López de Bertodano succession. Rich palynomorph floras suggest a middle Campanian Age. Deposition was in low energy, shallow shelf environments. Invertebrate and palynomorph fossils, and lithology, all indicate correlation of the Eocene beds with the basal La Meseta Formation, members Telm 1 and lower Telm 2 of Seymour Island. The age of these beds is probably late early Eocene. The basal La meseta sands are marginal marine to shallow shelf sediments that fill a broad valley probably incised during latest Paleocene-earliest Eocene as a result of tectonism and sea-level lowstands.

First record of the family Ringiculidae (Gastropoda) from the Middle Tertiary of Antarctica

A new species of the late Mesozoic–Cenozoic family Ringiculidae (Ringicula(Ringicula)cockburnensisn. sp.) is described from basal glauconitic beds of late Eocene age of Cockburn Island, Antarctica, and is the first reported occurrence of the family Ringiculidae from the continent of Antarctica.Ringicula (R.) cockburnensisn. sp. most closely resemblesR. castigatafrom the middle Oligocene Duntroonian Stage of New Zealand and provides further support for the strong provinciality (Weddellian Province) that existed along the southern margin of the Pacific during the Late Cretaceous and early Tertiary.

Late tertiary glaciation and sea-level changes in Antarctica

The age and history of the present Antarctic ice sheet have long been matters of speculation. Reports of Tertiary glaciation in Antarctica have been based on the presence of till-like deposits, only one of the several criteria proposed for the recognition of older glaciations. Nichols reviewed all reports suggesting a Tertiary beginning and concluded that the evidence was not compelling. Continued field and laboratory study of deposits, both marine and terrestrial, has provided an increasing amount of evidence to indicate a Tertiary beginning for Antarctic and possibly Arctic glaciations. In western Antarctica the Jones Mountains provide some detailed information that bears on the question. The Jones Mountains consist of a mainly granitic Mesozoic basement complex, truncated by a major erosional unconformity which is overlain by as much as 500 m of Late Tertiary volcanics. The erosion surface is essentially horizontal, and is marked by grooves, striations, chatter-marks, and other evidences of planation. Lenses of a till-like material occur at the base of the overlying volcanics. The areal extent, low relief, and freshness of the markings on the surface lead to the conclusion that Tertiary glaciation is involved. The physical and mineralogical characteristics of the till-like material indicate that glacier ice was probably present at the time of eruption of the volcanics. The evidence for sea-level changes in Antarctica since Tertiary time is difficult to interpret. Numerous strandlines have been called Recent. Most of the former shorelines are probably now buried under the ice cover although the Tertiary Pecten Conglomerate rests on a wave-cut platform 220–250 m high on Cockburn Island. The location, interpretation, and dating of former shorelines remain one of the little studied phases of Antarctic geomorphology.

Ferns of Manitoulin Island, Ontario (Continued)

7. PTERIDIUM AQUILINUM (L.) Kuhn var. IATIUSCULUM (Desv.) Underw. ex Heller-In open rocky woods, McKim's Beach, 14 Sept. 1961, S 9332. Sight records: Barrie Is., Bluejay Creek, Cape Robert, Christina Bay, Cook's Dock, Dean Bay, Evansville, Frechette Bay, Gore Bay, Green Bay, High Hill, Honora, Ice Lake, James Bay, Kaboni, Manitou Lake, 5 & 8 miles SW of Manitowaning, Marsh Lake, Mindemoya, Mississagi Strait, Mud Lake, Perch Lake, Poole Lake, Providence Bay, Roberts Bay to Thomas Bay, Silver Lake, Silverwater, Sounding Cove, South Baymouth, West Bay, Windfall Lake; Cockburn Is.; Great, Outer, and Western Duck Islands; Baie Fine; Killarney. Bracken occurs almost everywhere in the district and is abundant. Other collections: Providence Bay, Wekwemikongsing, and Cockburn Is., C. 0. Grassl 5859, 5877 4 5879 (MICH); 2 miles NW of Manitowaning, H. H. Brown 5579 (TRT); Fossil Hill, K. K. Irizawa 134 (TRT). 8. CRYPTOGRAMMA STrLLERI (S. G. Gmel.) Prantl-On rocks of escarpment overlooking West Bay, 26 July 1956, S 4. F 6607; rock face of wooded ridge, Mud Lake, 5 July 1957, S & G 7164; mossy crevices of limestone in shady woods 8 miles SW of Manitowaning, 7 June 1959, S 4 H 8444; mossy crevices of limestone cliffs at top of escarpment, 1 mile N of Green Bay, 15 July 1959, S 4 H 8779; crevices of limestone cliff, East Bluff, 1 mile NE of Gore Bay, 24 July 1959, S 4 H 8973. Sight records: Cook's Dock, Evansville, Ice Lake, Manitowaning, Michael Bay, Mindemoya. The Slender Cliff-brake is locally abundant on cliff faces and shaded limestone ridges. Other collections: Gore Bay, Battery Bluff and near Rattlesnake Harbour, C. O. Grassl 1517, 1636, 4 5889 (MICH); High Falls, Pease Ogden 25059 (GH, TRT); 2 miles N of Murphy Point, Senn 4. Lindsay 5437 (DAO, TRT). Reported from McLeod Harbour on Cockburn Island by Bell (1870), as Allosorus gracilis; the specimen which I have seen from Bell's collection at Carleton University (CCO), labelled Is. may have been taken on Cockburn Island. 9. ADIANTUM PEDATUM L.-I have seen the Maidenhair Fern on Manitoulin Island only once, in woods along the Manitou River near Michael Bay on 28 July 1952, in company with John Clayson. Since this species is common in most of Southern Ontario (Fig. 2) no voucher was taken at that time. Its rarity on the island was realized only later when the data were being examined for the preparation of this paper. I have also seen a specimen from a garden in Gore Bay to which the fern was said to have been trans71