Andrzej Gaździcki

The Eocene expansion of nautilids to high latitudes

Abstract A short-term return of environmental conditions similar to those of the end-Cretaceous is marked by the reappearance of nautiloid cephalopods in the lower-middle Eocene La Meseta Formation of Seymour Island, Antarctic Peninsula. Previous findings have been supplemented by a collections of 33 specimens. The nautiloids come from several horizons, the oldest sample apparently being located close to the base of the formation (Telm1), the most numerous coming from the Cucullaea bed of Telm2 and 3. A few specimens were collected from Telm4–6. The La Meseta Formation nautiloid assemblages developed apparently in response to one of the Eocene warmings and resulting transgression of a warm sea. The incursion of nautiloids into southern high latitudes was roughly coeval with their expansion to the northern European seas and the succession of faunas was parallel in both regions. Based on the analogy with the lower Eocene London Clay nautiloid assemblages an estimate of bathymetric evolution of the environment can be made by. The presence of a relatively shallow-water form similar to Cimomia imperialis close to the base of the lower-middle Eocene La Meseta Formation (Telm1) marks the beginning of the marine transgression. The dominant La Meseta species, Euciphoceras argentinae, was apparently an analogue of the English E. regale, the occurrence of which in the London Clay corresponds to the highest sea level stand. The presence of Aturia in the higher part (Telm4 and 5) of the La Meseta Formation suggests that cold oceanic waters possibly entered the area, accompanied by a sea-level drop. The last nautiloid (Telm6) is an Euciphoceras sp., interpreted to be indicative of shallower habitat depth limits. Both incursion of the nautiloids to, and their disappearance from the Eocene high latitudes were connected with a fundamental rearrangement of the geographic distribution of particular lineages.

Foraminifera from the Eocene La Meseta Formation of Isla Marambio (Seymour Island), Antarctic Peninsula

Abstract Benthic foraminiferal assemblages are described for the first time from the early Eocene of West Antarctica. They come from the lower member (Telm1) of the La Meseta Formation of Isla Marambio (Seymour Island). Two distinctive assemblages, dominated by Nonionellina, Nonionella, Globocassidulina, and Eilohedra, as well as by Globocassidulina, Cribroelphidium, Guttulina, and Lobatula, indicate restricted, shallow marine, nearshore conditions. Their most characteristic species show distinct affinities with Eocene faunas of New Zealand and Patagonia, as well as with stratigraphically younger Antarctic foraminiferal communities.

TheChlamys coquinas in glacio-marine sediments (Pliocene) of King George Island, West Antarctica

SummaryThe fossiliferous glacio-marine sequence of the “Pecten conglomerate” (=Low Head Member of the Polonez Cove Formation) of King George Island contains numerous pelecypod shells ofChlamys anderssoni (Hennig), which sometimes form lumachelles. These allochthonous coquinas, often with intraclasts, can be interpreted as storm deposits (tempestites). Their mode of distribution in the deposits of the Low Head Member suggests that sedimentation of this sequence was episodically interrupted by storm-generated energy events resulting in resedimentation of the biota assemblages.ZusammenfassungDie fossilführende glaziomarine Serie des “Pecten-Konglomerats” (Low Head Einheit der Polonez Cove Formation) der King George Insel besteht hauptsächlich aus Schalen der MuschelChlamys anderssoni (Hennig), die manchmal Schillagen bilden. Diese allochthonen Lumachellen, die oft Intraklasten enthalten, können als Sturmsedimente (Tempestite) interpretiert werden. Ihr Verteilungsmuster innerhalb der Low Head Einheit deutet darauf hin, daß die Ablagerung dieser Serie episodisch von sturmbedingten hochenergetischen Ereignissen unterbrochen wurde, die eine Resedimentation von Muschelschalen verursachten.

Short Note: An ibis-like bird from the Upper La Meseta Formation (Late Eocene) of Seymour Island, Antarctica

Ibises are a group of medium- to large-sized, mainly wading birds in the family Threskiornithidae (Aves: Ciconiiformes; see also discussion in Mayr 2002). They are known from all the continents except Antarctica, though one species breeds as far south as Tierra del Fuego (del Hoyo et al. 1992, p. 499). The oldest fossil bones (including skull elements) attributed to ibises are those of Rhynchaeites messelensis Wittich, 1898 from the Middle Eocene of Messel, Germany (Peters 1983, Mayr 2002). Another supposed member of this group is the Pondaung bird from the late Middle Eocene of Myanmar (formerly Burma) represented solely by an incomplete tibiotarsus (Stidham et al. 2005, fig. 2). The taxonomic position of Minggangia changgouensis Hou, 1982 from the Late Eocene of China (Hou 1982) was recently questioned by Stidham et al. (2005, p. 183). Here, we present a partial bill from the Eocene La Meseta Formation (Seymour Island, Antarctica) which most closely resembles that of ibises.

Paleoenvironments during the Rhaetian transgression and the colonization history of marine biota in the Fatric Unit (Western Carpathians)

Abstract Terminal Triassic environmental changes are characterized by an integrated study of lithology, litho- and cyclostratigraphy, paleontology, mineralogy, geochemistry and rock magnetism in the Tatra Mts. The Carpathian Keuper sequence was deposited in an arid environment with only seasonal rivers, temporal lakes and swamps with scarce vegetation. Combination of a wide range of δ18O values (-0.7 to + 2.7) with negative δ13C values documents dolomite precipitation either from brackish or hypersaline lake water, or its derivation from pore water comparably to the Recent Coorong B-dolostone. Negative δ13C values indicate microbial C productivity. Rhaetian transgressive deposits with restricted Rhaetavicula fauna accumulated in nearshore swamps and lagoons. Associations of foraminifers, bivalves and sharks in the Zliechov Basin were controlled by physical factors. Bivalve mollusc biostromes were repetitively destroyed by storms, and temporary firm bottoms were colonized by oysters and burrowers. Subsequent black shale deposition recorded input of eolian dust. Bottom colonization by pachyodont bivalves, brachiopod and corals started much later, during highstand conditions. Facies evolution also revealed by geochemical data, C and O isotope curves reflect eustatic and climatic changes and help reconstruct the evolution of Rhaetian marine carbonate ramp. The Fatra Formation consists of 100 kyr eccentricity and 40 kyr obliquity cycles; much finer rhythmicity may record monsoonlike climatic fluctuations. Fluvial and eolian events were indicated by analysis of grain size and content of clastic quartz, concentrations of foraminiferal (Agathammina) tests in thin laminae indicates marine ingression events. Magnetic susceptibility (MS) variations reflect the distribution of authigenic and detrital constituents in the sequence. Increasing trend of MS correlates with the regressive Carpathian Keuper sequence and culminates within the bottom part of the Fatra Formation. Decreasing trend of MS is observed upwards the transgressive deposits of the Fatra Formation.

Dasycladacean alga Palaeodasycladus in the northern Tethys (West Carpathians, Poland) and its new palaeogeographic range during the Early Jurassic

The green alga Palaeodasycladus was recognized in Lower Jurassic shallow-marine high-energy calcarenites of the Choč Nappe (Hronicum Domain) in the Tatra Mts in Poland. This occurrence indicates the most Northern record of Palaeodasycladus as it is known mostly from the southern part of the Western Tethys. The stratigraphic range of Palaeodasycladus (Norian, Sinemurian–Pliensbachian) and the upper Pliensbachian age of the overlying calcarenites (previous data on the basis of brachiopods) suggest that the studied part of the section was deposited during the Sinemurian–early Pliensbachian. The previous and current reports on occurrences of Palaeodasycladus allowed determination of a new northern palaeogeographic range of the shallow-marine Mediterranean biota during the Early Jurassic time.

Lower Jurassic Bahamian-type facies in the Choč Nappe (Tatra Mts, West Carpathians, Poland) influenced by paleocirculation in the Western Tethys

The Lower Jurassic (upper Sinemurian) of the Hronicum domain (Tatra Mts., Western Carpathians, Poland) represents typical tropical shallow-water carbonates of the Bahamian-type. Eight microfacies recognized include oolitic-peloidal grainstone/packstone, peloidal-bioclastic grainstone, peloidal-lithoclastic-bioclastic-cortoidal grainstone/packstone, peloidal-bioclastic packstone/grainstone, peloidal-bioclastic wackestone, spiculitic wackestone, recrystallized peloidal-oolitic grainstone and subordinate dolosparites. The studied sediments were deposited on a shallow-water carbonate platform characterized by normal salinity, in high-energy oolite shoals, bars, back-margin, protected shallow lagoon and subordinately on restricted tidal flat. Some of them contain the microcoprolite Parafavreina, green alga Palaeodasycladus cf. mediterraneous (Pia) and Cayeuxia, typical of the Early Jurassic carbonate platforms of the Western Tethys. The spiculite wackestone from the upper part of the studied succession was deposited in a transitional to deeper-water setting. The studied upper Sinemurian carbonates of the Hronicum domain reveal microfacies similar to the other Bahamian-type platform carbonates of the Mediterranean region. Thereby, they record the northern range of the Lower Jurassic tropical shallow-water carbonates in the western part of the Tethys, albeit the thickness of the Bahamian-type carbonate successions generally decrease in a northerly direction. The sedimentation of the Bahamian-type deposits in the Hronicum domain, located during the Early Jurassic at about 28°N, besides other specific factors (i.e., light, salinity, and nutrients) was strongly controlled by the paleocirculation of warm ocean currents in the Western Tethys.

A New Sediment-Dwelling Pholadid Bivalve from Oligocene Glaciomarine Sediments of King George Island, West Antarctica

We present a re-description of the pholadid bivalve from the Oligocene Polonez Cove Formation, King George Island, West Antarctica, previously identified as Penitella sp. The study is based on a collection of 210 specimens, preserved exclusively in life position in flask-shaped Gastrochaenolites type borings which have been subsequently buried by glaciomarine diamictite. The systematic study showed that this pholadid is a new species belonging to the genus Pholadidea rather than to Penitella and we name it Pholadidea gradzinskii sp. nov. The species is one of very few Late Cretaceous—Paleogene pholadids that we could safely identify as Pholadidea. All of them are known exclusively from the southern Pacific and adjacent areas (New Zealand, Antarctica, and Patagonia). We demonstrate that the genus attained its Recent broad distribution before the middle Miocene, when the first species of Pholadidea appeared in the Northern Hemisphere. The mass occurrence of P. gradzinskii in the Oligocene of West Antarctica results from favourable living condition in a shallow marine environment. Low sedimentation rate allowed the settlement of numerous larvae and their subsequent metamorphosis, growth, and maturity terminated by the mass mortality caused by the burial by marine diamictite. The sediment-boring Paleogene species of Pholadidea, among them P. gradzinskii, follow the wood-boring Late Cretaceous species P. (Hatasia) wiffenae, which reflects a general pattern of evolution of substrate selection among pholadoid bivalves.