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The Cretaceous period is particularly well represented by a thick sequence of clastic sedimentary rocks exposed in the Antarctic Peninsula region of western Antarctica. This was an active margin throughout the Late Mesozoic and in total some 7km+ of Cretaceous sedimentary rocks accumulated in a series of fore-, intra-, and back-arc basins. The Fossil Bluff Group of eastern Alexander Island can be traced from the Jurassic - Cretaceous boundary into the Upper Albian and represents a broad-scale shallowing-upwards sequence from deep marine to a prominent Upper Albian fluvial interval in which high density forests developed at a palaeolatitude of 75°S. The Cretaceous sequence exposed in the James Ross Island group continues right through the Upper Cretaceous to the K–Pg boundary. The Campanian - Maastrichtian succession in particular is over 2km in total thickness and richly fossiliferous. The improved Cretaceous stratigraphy of Antarctica is an invaluable terrestrial record of climatic change at a high palaeolatitude. This includes a gradual increase in temperature to the Cretaceous Thermal Maximum, and then a decline to the K–Pg boundary. There may be no simple link between these palaeotemperature changes and Cretaceous patterns of biotic radiation and extinction.

The Fossil Bluff Group of eastern Alexander Island records the exceptional preservation of more than 8 km of Mesozoic sedimentary rocks deposited into an accretionary forearc basin that developed unconformably above a late Paleozoic accretionary complex, and in proximity to a continental margin arc during a prolonged phase of enhanced magmatism. Through the Mesozoic, the Fossil Bluff Group evolved from a trench-slope environment to a forearc basin sourced from the continental margin arc. During this period, the Antarctic Peninsula’s convergent margin was characterized by episodes of magmatic flare-ups that developed during tectonic compression, crustal thickening, extension, and uplift. U-Pb and Lu-Hf detrital zircon data are used to determine the provenance of the forearc succession and as a monitor of arc magmatic tempos during the late Mesozoic. The magmatic record in the adjacent arc is poorly preserved or partially absent, but the sedimentary record of the forearc basin preserves a largely uninterrupted record of arc magmatism that can be studied with detrital zircon geochronology and geochemistry. The basal succession of the Fossil Bluff Group is sourced from the adjacent accretionary complex, but thereafter it is strongly controlled by the proximal arc in western Palmer Land and is characterized by a mixed arc/recycled signature during episodes of renewed sedimentation. However, the main phases of deposition during the Early Jurassic (ca. 180 Ma), Early Cretaceous (141−131 Ma), and mid-Cretaceous (125−102 Ma) are dominated by arc-only sources. The Lu-Hf isotopic record supports a transition from convergence to extension and a return to convergence during the Mesozoic, which is consistent with accretionary orogens from elsewhere along the West Gondwanan margin. The provenance record during the depositional history of the basin points overwhelmingly to an autochthonous origin; as such, models for parts of the western province of the Antarctic Peninsula being al

Lower Paleocene marine siliciclastics of the Sobral Formation (Seymour Island, Antarctica) form an important component of a key southern high latitude reference section for the Maastrichtian–Eocene. The formation comprises a coarsening-upward, regressive succession (270 m thick), shallowing from prodeltaic, mud-rich to sandy nearshore sediments. Sedimentary facies analysis, integrated with macrofaunal and microfloral palaeoecological studies, indicate a wave-dominated, tidally influenced deltaic environment. Four depositional sequences (1–4) record the role of relative sea-level changes in controlling the stepwise progradation of the system. Prodeltaic and distal delta-front deposits (Sequences 1, 2), comprise coarsening-upward parasequences of mud-rich heteroliths and bioturbated fine-grained muddy sands displaying draped slump scars. The overlying erosional sequence boundary is marked by incised valleys filled with fluvio-estuarine sediments; succeeding sand-rich facies (Sequences 3, 4) represent the proximal delta front and delta platform. The macro-invertebrate and palynological datasets display contrasting responses to the regressive history of the formation. The macrofaunal record in the distal deltaic sediments reflects the marine influence, though a stratigraphic increase in diversity was controlled both by ecological factors and biotic recovery following the K–Pg event. The associated palynological assemblage also displays a strong marine signal and includes typical outer neritic – oceanic dinoflagellate cyst taxa. A sharp decline in macrofossil diversity and abundance in Sequences 3, 4 is compatible with ecological stress in shallow-water, restricted inshore settings. Though the palynological record at this level is terrestrially dominated, the marine component reflects the cosmopolitan nature of dinoflagellates, displaying the highest diversities in the formation. The regressive Sobral Formation ended a protracted c. 60 Myr history of regional subsidence

The Late Cenozoic flourishing of polar marine ecosystems, just when temperatures were reaching their lowest levels, has always seemed anomalous. Such an observation is coupled with an increasing volume of molecular phylogenetic evidence to indicate that some polar taxa radiated at exceptionally high evolutionary rates. The canonical latitudinal diversity gradient (LDG) may not be underpinned by a parallel gradient in evolutionary rates. This study provides a review of this critical question.

Aim: The aim was to investigate the evolutionary origins of the striking biodiversity contrast between high- and low-latitude regions in the present day. Is this a relatively recent phenomenon, causally linked in some way to the greenhouse–icehouse transition and onset of global cooling c. 34 Myr ago, or does it have deeper temporal roots and thus other potential causes? Location: Early Cenozoic fossil assemblages from two tropical and one polar region, and modern counterparts from various tropical localities and Antarctica. Time period: The Cretaceous–Palaeogene (K/Pg) mass extinction event, Early Cenozoic (Palaeocene–Eocene) and the present day. Major taxa studied: Shelf-depth marine Mollusca; the four richest modern benthic clades: Imparidentia, Pteriomorphia, Neogastropoda and Littorinimorpha. Methods: The K/Pg mass extinction and subsequent recovery was compared between two tropical and one polar region at four distinct stratigraphic intervals. Taxa were identified to species level and assigned to principal families within the four largest benthic molluscan clades. Taxon counts were compared between the three regions at each level and also compared with standardized tropical and polar modern faunas. Results: The mass extinction was followed by a distinct 25 Myr phase of evolutionary radiation, during which the tropical–polar contrast in the taxonomic composition of all four clades was strongly enhanced; as the global molluscan fauna expanded, it differentiated into distinct low- and high-latitude components. Main conclusions: A marked differentiation of tropical and polar molluscan faunas occurred in the immediate aftermath of the K/Pg mass extinction; it is likely that, at least for the two bivalve clades investigated, this differentiation was initiated well within the Mesozoic era. The greater antiquity of the tropical–polar split suggests that it was not the product of any single controlling factor during the Cenozoic.

We are beginning to appreciate that the huge radiations of both marine and terrestrial taxa in the aftermath of the K/Pg mass extinction event were concentrated largely, but not exclusively, in the low-latitude and tropical regions. This in turn means that significant latitudinal diversity gradients were developed well before the onset of global cooling at the Eocene/Oligocene boundary. Net rates of evolutionary radiations were significantly higher through the Early Paleocene – Middle Eocene interval (i.e. ~62–42 Ma) in the tropics than at the poles but this may be due as much to their retardation in the latter regions as to their acceleration in the former. At least in the marine realm, polar assemblages are characterised by the phenomenon of high dominance/low evenness, and it is thought likely that this is due to the extreme seasonality of primary production at the base of the food chain. Many modern polar marine organisms are de facto trophic generalists and occupy significantly broader ecological niches than their tropical counterparts. Although we cannot dismiss the roles of both temperature and area in promoting tropical diversity, it could well be that LDGs are just as much the product of a latitudinal gradient in the seasonality of primary productivity. Such a gradient would have operated in both greenhouse and icehouse worlds.

We review the evidence for predation of shelly benthic prey over 125 million years of earth history in the James Ross Basin, Antarctica (~65°S). Although poor in the Early Cretaceous lower parts of the sequence, which represent essentially deeper water facies, evidence for both potential crushers and drillers becomes more apparent in the Santonian – Campanian Santa Marta Formation, and by the Maastrichtian López de Bertodano Formation there is an extensive fossil record of drill holes attributable to naticid gastropods, and some evidence of crushing by decapods crustaceans and possibly other taxa too. This continues at a similar level of intensity across the K/Pg boundary into the Danian Sobral Formation, but is less well constrained in the latest Paleocene – Early Eocene. The most extensive record of predation occurs in the Middle Eocene section of the La Meseta Formation on Seymour Island which also records the highest levels of benthic diversity within the entire basin. This key section is providing some important new evidence to suggest that the rate of acceleration of benthic predation intensity through the Late Mesozoic – Early Cenozoic in the polar regions may be similar to that seen in lower latitude regions. Predator – prey interaction was a key factor in the evolution of polar marine faunas too.

Taxonomic and ecological recovery from the Cretaceous–Palaeogene (K–Pg) mass extinction 66 million years ago shaped the composition and structure of modern ecosystems. The timing and nature of recovery has been linked to many factors including palaeolatitude, geographical range, the ecology of survivors, incumbency and palaeoenvironmental setting. Using a temporally constrained fossil dataset from one of the most expanded K–Pg successions in the world, integrated with palaeoenvironmental information, we provide the most detailed examination of the patterns and timing of recovery from the K–Pg mass extinction event in the high southern latitudes of Antarctica. The timing of biotic recovery was influenced by global stabilization of the wider Earth system following severe environmental perturbations, apparently regardless of latitude or local environment. Extinction intensity and ecological change were decoupled, with community scale ecological change less distinct compared to other locations, even if the taxonomic severity of the extinction was the same as at lower latitudes. This is consistent with a degree of geographical heterogeneity in the recovery from the K–Pg mass extinction. Recovery in Antarctica was influenced by local factors (such as water depth changes, local volcanism, and possibly incumbency and pre‐adaptation to seasonality of the local benthic molluscan population), and also showed global signals, for example the radiation of the Neogastropoda within the first million years of the Danian, and a shift in dominance between bivalves and gastropods.

The shell material of marine benthic bivalves provides a sensitive archive of water chemistry immediately above the sediment–water interface, which in turn is affected by sedimentary geochemistry and redox reactions. Sulfate has a major controlling effect on sedimentary carbon cycling, particularly the processes of methane production and oxidation, with lower concentrations of sulfate likely resulting in an increase in sedimentary methane production. Whilst it is accepted that ocean sulfate varied markedly across the Phanerozoic, evidence of changes in methane production in sediments has so far been lacking. There is potential for the oxidation products of sedimentary methane to be preserved and detected in marine fossils. Here we present the results of high resolution carbonate isotope records from two taxa of well-preserved shallow-infaunal bivalve (Lahillia and Cucullaea) collected from the marine shelf succession across the Cretaceous–Paleogene (K–Pg) boundary in Seymour Island, Antarctica. The succession has pre-existing subtle indications of more abundant methane, and the time period is characterized by much lower marine sulfate concentrations than modern. These shell carbonate–carbon isotope records vary widely: at one extreme, shells have typical average values and small ranges compatible with a contemporaneous marine dissolved inorganic carbon (DIC) source and modern-style sedimentary carbon cycling. At the other, the shells have large-amplitude annual cycles of carbon isotopic variability of up to 23.8‰ within a single year of growth and shell carbonate δ13δ13C compositions as negative as −34‰. Shells with these increased ranges and unusually negative values are found at discrete intervals and across both bivalve taxa. The contribution of methane required to explain the most negative carbonate–carbon isotopic values in the bivalve shells is extremely high (between 30 to 85% of bottom-water DIC based on mass balance calculations). Records of organic-carbon

The Cretaceous–Paleogene (K–Pg) mass extinction event 66 million years ago led to large changes to the global carbon cycle, primarily via a decrease in primary or export productivity of the oceans. However, the effects of this event and longer-term environmental changes during the Late Cretaceous on the global sulfur cycle are not well understood. We report new carbonate associated sulfate (CAS) sulfur isotope data derived from marine macrofossil shell material from a highly expanded high latitude Maastrichtian to Danian (69–65.5 Ma) succession located on Seymour Island, Antarctica. These data represent the highest resolution seawater sulfate record ever generated for this time interval, and are broadly in agreement with previous low-resolution estimates for the latest Cretaceous and Paleocene. A vigorous assessment of CAS preservation using sulfate oxygen, carbonate carbon and oxygen isotopes and trace element data, suggests factors affecting preservation of primary seawater CAS isotopes in ancient biogenic samples are complex, and not necessarily linked to the preservation of original carbonate mineralogy or chemistry. Primary data indicate a generally stable sulfur cycle in the early-mid Maastrichtian (69 Ma), with some fluctuations that could be related to increased pyrite burial during the ‘mid-Maastrichtian Event’. This is followed by an enigmatic +4‰ increase in δ34SCAS during the late Maastrichtian (68 to 66 Ma), culminating in a peak in values in the immediate aftermath of the K–Pg extinction which may be related to temporary development of oceanic anoxia in the aftermath of the Chicxulub bolide impact. There is no evidence of the direct influence of Deccan volcanism on the seawater sulfate isotopic record during the late Maastrichtian, nor of a direct influence by the Chicxulub impact itself. During the early Paleocene (magnetochron C29R) a prominent negative excursion in seawater δ34S of 3–4‰ suggests that a global decline in organic carbon burial related

A survey of 759 predatory drill holes in Late Cretaceous and Paleogene molluscan and serpulid worm prey from Seymour Island (Antarctica) has allowed exploration of the effects of the K-Pg mass extinction on predator-prey dynamics at this high latitude site. Circular holes (0.62–6.41 mm in diameter), suggesting a large gastropod predator, most probably “Vanikoropsis” arktowskiana, occur throughout the study interval. Analysis suggests that the driller was a catholic predator capable of attacking a range of prey types, showing some degree of size and stereotypic handling behaviour. Although there were changes in prey choice across the extinction event, these reflect changes in available prey, and in particular limited options immediately post extinction. There were no significant changes in failure rate (Prey Effectiveness) over the mass extinction. Our findings suggest that at this site, for this particular predator, aside from menu choice, predation dynamics post-extinction was “business as usual”.

We are beginning to appreciate that the origin of the modern Antarctic marine fauna is related to a series of key events throughout the Cenozoic era. In the first of these, the mass extinction at the Cretaceous–Palaeogene boundary (66 Ma) reset the evolutionary stage and led to a major radiation of modern taxa in the benthic realm. Although this took place in a greenhouse world, there is evidence to suggest that the radiation was tempered by the seasonality of primary productivity, and this may be a time‐invariant feature of the polar regions. Although there could well have been a single, abrupt extinction event at c. 34 Ma, there is also evidence to suggest a phased extinction of various taxa over a period of millions of years. Important new molecular phylogenetic data are indicating that a wide variety of both benthic and pelagic taxa radiated shortly after a second major phase of cooling at c. 14 Ma. Such a phenomenon is linked to a series of major palaeoceanographic changes, which in turn led to a proliferation of diatom‐based ecosystems. Although the modern benthic marine fauna can be traced back some 45–50 Myr, a substantial component of the modern pelagic one may be less than 14 Myr old. The latter is also characterized by assemblages of high abundance but comparatively low species richness and evenness. A distinctive signature of low diversity but high dominance within Antarctic marine assemblages was maintained by the interplay between temperature and primary productivity throughout the Cenozoic.

The large, burrowing bivalve Laternula elliptica is an abundant component of shallow-water soft-substrate communities around Antarctica but its congeners are temperate and tropical in distribution and their phylogenetic relationships are obscure. A new molecular analysis of Laternulidae species shows that there are two distinct clades, one of Exolaternula species, E. spengleri and E. liautaudi, possessing a ligamental lithodesma and a larger clade of species lacking the lithodesma. Of the latter, Laternula elliptica is a sister taxon to temperate and tropical species, including those that live around the coasts of Australia from Tasmania to Darwin. It is suggested that L. elliptica was left isolated around Antarctica following the opening of the Tasman Gateway and initiation of the Circum-Antarctic Current as Australia drifted northwards following the final breakup of Gondwana. A further scenario is that as Australia moved closer to Asia, species spread into tropical habitats and more widely to the Red Sea and Japan. Exolaternula species have a likely Tethyan origin and the present-day range is from the Arabian Gulf, around southern Asia and as far north as southern Russia.

Debate continues about the nature of the Cretaceous–Paleogene (K–Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K–Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous–Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian.

The prohibition of commercial mineral resource extraction through the Antarctic Treaty System has removed one significant source of potential damage to Antarctica's geological and geomorphological values. However, given the on-going increase in Antarctic tourism and scientific footprint, some high-quality geological features may be vulnerable to human impact, such as damage due to the construction of logistical facilities, unregulated collection of geological specimens or oversampling for scientific purposes. The Protocol on Environmental Protection to the Antarctic Treaty puts in place a framework for the protection of Antarctica's environmental, scientific, historic, wilderness and aesthetic values. However, the Antarctic Protected Area system is still immature and further implementation of existing management tools may be required to protect the diverse range of vulnerabilities, qualities and spatial scales represented in the geology and geomorphology of the continent. At sites where high-quality mineralogical or palaeontological specimens exist in limited quantities, considerations of how best to prevent oversampling and manage access to remaining material may be supported by assessment of cumulative impacts. Examination of the level of Antarctic specimen loans from a selection of national geological collections suggested that existing publically accessible geological collections could be better utilized, which could reduce environmental impact and oversampling at vulnerable Antarctic sites.

Fossil hydrocarbon seeps are present in latest Cretaceous (Maastrichtian) volcaniclastic shallow shelf sediments exposed on Snow Hill and Seymour Islands, James Ross Basin, Antarctica. The seeps occur in the Snow Hill Island Formation on Snow Hill Island and are manifest as large-sized, cement-rich carbonate bodies, containing abundant thyasirid bivalves and rarer ammonites and solemyid bivalves. These bodies have typical seep cement phases, with δ13C values between − 20.4 and − 10.7‰ and contain molecular fossils indicative of terrigenous organic material and the micro-organisms involved in the anaerobic oxidation of methane, including methanotrophic archaea and sulphate-reducing bacteria. On Seymour Island the seeps occur as micrite-cemented burrow systems in the López de Bertodano Formation and are associated with thyasirid, solemyid and lucinid bivalves, and background molluscan taxa. The cemented burrows also have typical seep cement phases, with δ13C values between − 58.0 and − 24.6‰. There is evidence from other data that hydrocarbon seepage was a common feature in the James Ross Basin throughout the Maastrichtian and into the Eocene. The Snow Hill and Seymour Island examples comprise the third known area of Maastrichtian hydrocarbon seepage. But compared to most other ancient and modern seep communities, the James Ross Basin seep fauna is of very low diversity, being dominated by infaunal bivalves, all of which probably had thiotrophic chemosymbionts, but which were unlikely to have been seep obligates. Absent from the James Ross Basin seep fauna are ‘typical’ obligate seep taxa from the Cretaceous and the Cenozoic. Reasons for this may have been temporal, palaeolatitudinal, palaeobathymetric, or palaeoecological.

In Mexico, the Upper Jurassic to lowermost Cretaceous La Casita and coeval La Caja and La Pimienta formations are well-known for their abundant and well-preserved marine vertebrates and invertebrates. The latter include conspicuous inoceramid bivalves of the genus Anopaea not formally described previously from Mexico. Anopaea bassei (Lecolle de Cantú, 1967), Anopaea cf. stoliczkai (Holdhaus, 1913), Anopaea cf. callistoensis Crame and Kelly, 1995 and Anopaea sp. are rare constituents in distinctive Tithonian–lower Berriasian levels of the La Caja Formation and one Tithonian horizon of the La Pimienta Formation. Anopaea bassei was previously documented from the Tithonian of central Mexico and Cuba, while most other members of Anopaea described here are only known from southern high latitudes. The Mexican assemblage also includes taxa which closely resemble Anopaea stoliczkai from the Tithonian of India, Indonesia and the Antarctic Peninsula, and Anopaea callistoensis from the late Tithonian to ?early Berriasian of the Antarctic Peninsula. Our new data expand the palaeogeographical distribution of the high latitude Anopaea to the Gulf of Mexico region and substantiate faunal exchange, in the Late Jurassic–earliest Cretaceous, between Mexico and the Antarctic Realm.

One of the most expanded records to contain the final fortunes of ammonoid cephalopods is within the López de Bertodano Formation of Seymour Island, James Ross Basin, Antarctica. Located at ~ 65° South now, and during the Cretaceous, this sequence is the highest southern latitude onshore outcrop containing the Cretaceous-Paleogene (K–Pg) transition. We present comprehensive new biostratigraphic range data for 14 ammonite and one nautiloid species based on the collection of > 700 macrofossils from high-resolution sampling of parallel sedimentary sections, dated Maastrichtian to earliest Danian in age, across southern Seymour Island. We find evidence for only a single, abrupt pulse of cephalopod extinction at the end of the Cretaceous when the final seven ammonite species disappeared, consistent with most evidence globally. In the lead up to the K–Pg extinction in the James Ross Basin, starting during the Campanian, ammonite diversity decreased overall, but the number of endemic taxa belonging to the family Kossmaticeratidae actually increased. This pattern continued into the Maastrichtian and may be facies controlled, linked to changes in sea level and seawater temperature. During the early Maastrichtian, ammonite diversity dropped significantly with only two species recorded from the basal López de Bertodano Formation on Seymour Island. The subsequent diversification of endemic taxa and reappearance of long-ranging, widespread species into the basin resulted in an increase in ammonite diversity and abundance during the mid-Maastrichtian. This was coincident with an apparent period of warming temperatures and sea level rise interpreted from palynology and sedimentology, perhaps reflecting a high latitude expression of the Mid-Maastrichtian Event. Late Maastrichtian diversity levels remained stable despite reported climatic and environmental variation. Ammonite diversity patterns during the Maastrichtian parallel those of microfossil species such as nannofossil and pl

Constraining past fluctuations in global temperatures is central to our understanding of the Earth's climatic evolution. Marine proxies dominate records of past temperature reconstructions, whereas our understanding of continental climate is relatively poor, particularly in high-latitude areas such as Antarctica. The recently developed MBT/CBT (methylation index of branched tetraethers/cyclization ratio of branched tetraethers) paleothermometer offers an opportunity to quantify ancient continental climates at temporal resolutions typically not afforded by terrestrial macrofloral proxies. Here, we have extended the application of the MBT/CBT proxy into the Cretaceous by presenting paleotemperatures through an expanded sedimentary succession from Seymour Island, Antarctica, spanning the latest Maastrichtian and Paleocene. Our data indicate the existence of a relatively stable, persistently cool temperate climate on the Antarctic Peninsula across the Cretaceous-Paleogene boundary. These new data help elucidate the climatic evolution of Antarctica across one of the Earth's most pronounced biotic reorganizations at the Cretaceous-Paleogene boundary, prior to major ice-sheet development in the late Paleogene. Our work emphasizes the likely existence of temporal and/or spatial heterogeneities in climate of the southern high latitudes during the early Paleogene.

The extensive Late Cretaceous – Early Paleogene sedimentary succession of Seymour Island, N.E. Antarctic Peninsula offers an unparalleled opportunity to examine the evolutionary origins of a modern polar marine fauna. Some 38 modern Southern Ocean molluscan genera (26 gastropods and 12 bivalves), representing approximately 18% of the total modern benthic molluscan fauna, can now be traced back through at least part of this sequence. As noted elsewhere in the world, the balance of the molluscan fauna changes sharply across the Cretaceous – Paleogene (K/Pg) boundary, with gastropods subsequently becoming more diverse than bivalves. A major reason for this is a significant radiation of the Neogastropoda, which today forms one of the most diverse clades in the sea. Buccinoidea is the dominant neogastropod superfamily in both the Paleocene Sobral Formation (SF) (56% of neogastropod genera) and Early - Middle Eocene La Meseta Formation (LMF) (47%), with the Conoidea (25%) being prominent for the first time in the latter. This radiation of Neogastropoda is linked to a significant pulse of global warming that reached at least 65°S, and terminates abruptly in the upper LMF in an extinction event that most likely heralds the onset of global cooling. It is also possible that the marked Early Paleogene expansion of neogastropods in Antarctica is in part due to a global increase in rates of origination following the K/Pg mass extinction event. The radiation of this and other clades at ~65°S indicates that Antarctica was not necessarily an evolutionary refugium, or sink, in the Early – Middle Eocene. Evolutionary source – sink dynamics may have been significantly different between the Paleogene greenhouse and Neogene icehouse worlds.

The fossil community from the Early Miocene Cape Melville Formation (King George Island, Antarctica) does not show the archaic retrograde nature of modern Antarctic marine communities, despite evidence, such as the presence of dropstones, diamictites and striated rocks, that it was deposited in a glacial environment. Unlike modern Antarctic settings, and the upper units of the Eocene La Meseta Formation on Seymour Island, Antarctica, which are 10 million years older, the Cape Melville Formation community is not dominated by sessile suspension feeding ophiuroids, crinoids or brachiopods. Instead, it is dominated by infaunal bivalves, with a significant component of decapods, similar to present day South American settings. It is possible that the archaic retrograde structure of the modern community did not fully evolve until relatively recently, maybe due to factors such as further cooling and isolation of the continent leading to glaciations, which resulted in a loss of shallow shelf habitats.

Small chorate dinoflagellate cysts are common in Upper Cretaceous to Quaternary sedimentary successions around the Antarctic margin. Taxonomic confusion surrounding dinoflagellate cysts and acritarchs of similar morphology throughout the southern high palaeolatitudes has hitherto limited investigation of their palaeoecological significance. This study aims to solve the taxonomic problems, and to allow a new assessment of dinoflagellate cyst acmes. A detailed morphological study of new material from the López de Bertodano Formation of Seymour Island, Antarctic Peninsula, is presented. These dinoflagellate cysts are identified as Impletosphaeridium clavusWrenn & Hart 1988 emend. nov. Their gross morphology and their vast abundances in the James Ross Basin are strongly suggestive of dinoflagellate blooms. This scenario implies similarities to modern dinoflagellate cysts from the polar regions.

The widespread assumption that the origin of polar marine faunas is linked to the onset of major global cooling in the Late Eocene – Early Oligocene is being increasingly challenged. The Antarctic fossil record in particular is suggesting that some modern Southern Ocean taxa may have Early Eocene or even Paleocene origins, i.e. well within the Early Cenozoic greenhouse world. A global analysis of one of the largest marine clades at the present day, the Neogastropoda, indicates that not only is there a decrease in the number of species from the tropics to the poles but also a decrease in the evenness of their distribution. A small number of neogastropod families with predominantly generalist trophic strategies at both poles points to the key role of seasonality in structuring the highest latitude marine assemblages. A distinct latitudinal gradient in seasonality is temperature-invariant and would have operated through periods of global warmth such as the Early Cenozoic. To test this concept a second global analysis was undertaken of earliest Cenozoic (Paleocene) neogastropods and this does indeed show a certain degree of faunal differentiation at both poles. The Buccinidae, s.l. is especially well developed at this time, and this is a major generalist taxon at the present day. There is an element of asymmetry associated with this development of Paleocene polar faunas in that those in the south are more strongly differentiated than their northern counterparts; this can in turn be linked to the already substantial isolation of the southern high latitudes. The key role of seasonality in the formation of polar marine faunas has implications for contemporary ecosystem structure and stability.

Nuculid bivalves of the Cape Melville Formation (Early Miocene, King George Island) are reviewed. Ten bivalve taxa are listed from the formation in the families Nuculidae (two species), Sareptidae, Malletiidae, Limopsidae (two species), Limidae, Pectinidae, Hiatellidae, and Periplomatidae. The Nuculidae consist of two species of Leionucula Quenstedt, 1930. One of these, L. melvilleana n. sp., is described and the other consists of the two species named previously by Anelli et al. (2006), which are demonstrated to be synonymous and are assigned to the species Leionucula frigida (Anelli, Rocha-Campos, Santos, Perinotto & Quaglio 2006). This assemblage, dominated by protobranchs (89% of specimens), is a typical fauna of offshore soft substrates, with a few specimens transported from hard substrates nearby. The diversity of Nuculidae has decreased in the Antarctic region through the Cenozoic.

We 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 Sr-87/(86) Sr 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.

The GustavGroup of the James Ross Basin, Antarctic Peninsula, forms part of a major Southern Hemisphere Cretaceous reference section. Palynological data, chiefly from dinoflagellate cysts, integrated with macrofaunal evidence and strontium isotope stratigraphy, indicate that the Gustav Group, which is approximately 2.6 km thick, is Aptian–Coniacian in age. Aptian–Coniacian palynofloras in the James Ross Basin closely resemble coeval associations from Australia and New Zealand, and Australian palynological zonation schemes are applicable to the Gustav Group. The lowermost units, the coeval Pedersen and Lagrelius Point formations, have both yielded early Aptian dinoflagellate cysts. Because the overlying Kotick Point Formation is of early to mid Albian age, the Aptian/Albian boundary is placed, questionably, at the Lagrelius Point Formation–Kotick Point Formation boundary on James Ross Island, and this transition may be unconformable. Although the Kotick Point Formation is largely early Albian on dinoflagellate cyst evidence, the uppermost part of the formation appears to be of mid Albian age. This differentiation of the early and mid Albian has refined the age of the formation, previously considered to be Aptian–Albian, based on macrofaunal evidence. The Whisky Bay Formation is of late Albian to latest Turonian age on dinoflagellate cyst evidence and this supports the macrofaunal ages. Late Albian palynofloras have been recorded from the Gin Cove, lower Tumbledown Cliffs, Bibby Point and the lower–middle Lewis Hill members. However, the Cenomanian age of the upper Tumbledown Cliffs and Rum Cove members, based on molluscan evidence, is not supported by the dinoflagellate cyst floras and further work is required on this succession. The uppermost part of the Whisky Bay Formation in north-west JamesRoss Island is of mid to late Turonian age and this is confirmed by strontium isotope stratigraphy. The uppermost unit, the Hidden Lake Formation, is Coniacian in age on both

New palaeontological collections made from Upper Cretaceous strata exposed within the James RossBasin, Antarctica, include ten echinoid species. Five species are described for the first time from Antarctica, while four others, previously published by Lambert in 1910, are revised according to the new data. The described echinoids comprise two new species, Huttonechinus antarctica nov. sp. and Nordenskjoeldaster? australis nov. sp., specimens closely related to an European spatangoid, Micraster aff. regularis, and three taxa that cannot be named at the specific level owing to poor preservation. In total, the fauna comprises three species of regular echinoids, five holasteroids, and two spatangoids. The ten taxa range in age from Santonian to Early Maastrichtian. The richest faunas are those associated with the prolific Gunnarites antarcticus ammonite assemblage. Several forms show affinities with Australia, New Zealand, south-east Africa and South America. There are indications that this is an essentially deep shelf echinoid fauna.

At the present day the Class Bivalvia comprises some 8000 species, sub-divided into approximately 700 genera, 107 families, and 41 superfamilies (Morton, 1996, and references therein). It represents one of the most diverse invertebrate groups within the marine realm and is often portrayed as the end-product of a long-term, adaptive radiation (e.g. Stanley, 1977). Over the last 250 Ma, in particular, there has been a steady but inexorable rise in the number of bivalve taxa (Fig. 10.1), and today they have come to occupy a very broad spectrum of benthic habitats and trophic categories (e.g. Bottjer, 1985). This is what Morton (1996, p. 348) has referred to as the ‘expanding success of the Bivalvia’.

The origins of present day benthic marine faunas from both the Magellan and Antarctic provinces may lie as far back as the Early Cretaceous (approx. 130 Ma). This was the time of the first significant marine incursion across the Gondwana supercontinent and isolation of a high-latitude group of continents. It was also the probable time of formation of the temperate, Pacific-margin Weddellian Province, which extended from Patagonia, through Antarctica and New Zealand, to south-eastern Australia. Both palaeontological and phylogenetic evidence suggest that a number of living taxa (i.e. genera and families) from both provinces can be traced back to the Late Cretaceous-earliest Cenozoic interval. At this time there was no discernible gradient in taxonomic diversity from either southernmost South America or Australasia into Antarctica. The long, essentially temperate, Eocene epoch was followed by a period of major change during the ensuing Oligocene. At some time during this interval the Antarctic circum-polar current was fully formed and this led to a vicariant event between the Magellan and Antarctic faunas. However, it is important to stress that the intensification of circumpolar circulation also promoted at least some dispersal between various Subantarctic and Antarctic sites. In all probability, it was as late as the late Miocene (some 10-12 m.y. ago) before an intense pattern of thermal zonation (in both horizontal and vertical senses) was established in the world ocean. This may be the true time of full differentiation between the Magellan and Antarctic provinces. Although certain major groups, such as the bivalve molluscs and decapod crustaceans, have obviously declined within Antarctic regions through time, others, such as the bryozoans, echinoderms, amphipods and isopods appear to have flourished. The key to evolutionary success in cold polar waters may be not so much resistance to low temperatures, but the ability to exploit novel habitats and trophic regimes.