Tethyan Region Research Articles

The Roadian Stage of the Permian and problems of its global correlation

Ammonoids, conodonts, and fusulinids from the type sections of the Roadian and contiguous stages in western Texas and adjacent areas are analyzed and partially revised. Four successive Roadian ammonoid assemblages are distinguished and correlated with conodont zones; data on their distribution are presented. Based on the results obtained, the Roadian Stage is identified in the Boreal and Tethyan regions. Boundaries of the Roadian Stage defined accurately in the type sections of Texas are hardly recognizable elsewhere. Recognition of the upper boundary is especially difficult. Occurrence of Roadian fossils means that deposits of this age are present in a sequence, but they cannot be differentiated from underlying and overlying beds. Like in the type area, the stage lower boundary based on conodonts is above the level of significant changes in marine biota within the Boreal and Tethyan realms as well. The upper boundary is not marked by noticeable biotic events either. Correlation of the Roadian deposits is imprecise because their boundaries are formally established using distribution of relatively rare conodonts.

The marine Permian of East and Northeast Asia: an overview of biostratigraphy, palaeobiogeography and palaeogeographical implications

The Permian marine biostratigraphy, faunal successions and mutual correlations (where possible) throughout East and Northeast Asia are synthesized, region by region, based on both published literature and the author's field observations in certain parts of the region. The correlation of the Permian marine successions of NE Asia with the Permian international timescale and, in particular, with Gondwanan Permian marine sequences remains a major challenge, due to profound marine provincialism during the Permian. However, by employing biogeographically mixed faunas from East Asia (SE Mongolia, NE China, South Primorye of Far East Russia and the South Kitakami Terrane of Japan) as ‘biostratigraphic gateways’, coupled with some bipolarly and bi-temperately shared Permian marine taxa and faunas, it has been possible to correlate, with reasonable confidence, some of the high-palaeolatitude Permian marine rock units and faunas of NE Asia with those of the Tethyan region and Gondwana. Palaeobiogeographically, the Permian marine faunas of East and NE Asia are assigned to four major provinces: Verkolyman, Sino-Mongolian–Japanese, Cathaysian and Panthalassan provinces, on the basis of their palaeogeographical distribution patterns and characteristics of faunal assemblages. Of these, the Sino-Mongolian–Japanese Province has considerable significance for regional palaeogeographical, plate tectonic and palaeoceanographical reconstructions during the Middle Permian, because of its conspicuously mixed cool- and warm-water marine biota. The origin of this biogeographically mixed marine biota is interpreted to have resulted from a combination of some key factors, including the increased tectonic convergence between the Bureya–Jiamusi Terrane and the Sino-Korean Platform during the Permian and the intermingling of both warm- and cold-water ocean currents off the eastern coastal areas of the Bureya–Jiamusi Terrane and the Sino-Korean Platform during the Middle Permian.

Paleogeographic and paleoclimatic setting of Lower Cretaceous basins of East Asia and western North America, with reference to the nonmarine strata

Lower Cretaceous strata are widespread in East Asia and along the western coast of North America. In both regions, Cretaceous basins contain significant stratigraphic accumulations and can be thought of as along-strike equivalents. In East Asia, fore-arc basins were oriented parallel to and east of active magmatic arcs while in western North America extensive fore-arc successions accumulated west of the arc complexes. The greater extent of nonmarine, rift and back-arc basins in the East Asian region, and overall lower topographic development, was likely related to movement of the region away from ongoing subduction to the east. In western North America, by contrast, movement of the North American plate westwards towards the active subduction zone resulted in development of a volumetrically larger and topographically higher orogen than in East Asia. The active arc complexes in both regions exerted significant controls on paleoclimate. Interior basins of both Asia and North America, landward of arc complexes, were significantly drier than the coastal areas, due to rain-shadow phenomena in both regions. Although the proto-Pacific Ocean was likely much wider during Early Cretaceous time than it is today, we infer that similar oceanic circulation patterns existed and significantly affected climate and molluscan biogeographic assemblages of both East Asia and western North America: East Asia was dominated by warm water derived from the Tethyan regions, whereas west coast North America was influenced by cooler waters derived from high-latitudes.

Falsocalcifolium nov. gen. and revision of the tribe Calcifolieae (Mississippian, incertae sedis algae)

A new genus, Falsocalcifolium is described. The type species is F. punctatum (Maslov) emend. The genus is placed in the tribe Calcifolieae Shuysky emend. of the family Calcifoliaceae Termier, Termier and Vachard nomen translat. Consequently, the generic make-up of the tribe is emended, and is now considered to be composed of Frustulata Saltovskaya emend., Falsocalcifolium nov. gen., and Calcifolium Shvetsov and Birina emend. Evolution within the tribe is shown by the progressive development of more petaloid morphologies and changes in the number and relationships of the internal structures called filaments (interpreted here as the emplacements containing endosymbiotic cyanobacteria). This evolution is also related to palaeoecological factors. The representatives of the tribe are considered excellent biostratigraphic markers in several western Tethyan regions (e.g. Great Britain, Ireland, southern France, southern Spain), where they are widely represented, but their geographical distribution in other basins seems to be incomplete, and thus their use in biostratigraphic correlation is at the moment limited.

Early Permian bioevent in the fusulinacean fauna of South China

Analysis of a large database of the stratigraphic distribution of fusulinacean Foraminifera reveals an Early Permian event of significant decline of species diversity in South China. Data from Late Carboniferous to Early Permian sections without apparent unconformity in southwest China were evaluated to determine if the apparent pattern of species disappearance was caused by bias in fossil preservation associated with Early Permian sea-level changes. Statistical analysis suggests that the Early Permian event started in the Late Sakmarian with a significant drop of species diversity in the Robustoschwagerina ziyunensis Zone and continued through the Pamirina darvasica Zone of the Artinskian and into the Brevaxina dyhrenfurthi Zone of the Early Kungarian, resulted in a total loss of about 40% species diversity in the fusulinacean fauna. The Early Permian event is the most extensive bioevent in the history of fusulinacean Foraminifera at the species level although it is less significant at the generic level. Because a similar faunal change has been found among the fusulinacean assemblages in North America and in various regions of Tethys, this event may represent a major faunal turn-over in response to the Early Permian changes in sea level and could be of a global nature. Previous recognition of this event was hampered by Early Permian unconformities in North America and other regions of Tethys.

Early Cretaceous palynofloras from the Tanggula Mountains of the northern Qinghai-Xizang (Tibet) Plateau, China

Two sections of the Yanshiping Group in the Tanggula Mountains area of the Qinghai-Xizang (Tibet) Plateau, a remote part of western China, have yielded three types of palynomorph assemblages. Two of these clearly indicate that the Xueshan Formation and parts of the diachronous Suowa and Xiali formations were deposited during the early Cretaceous (Berriasian–?Barremian). Largely on negative evidence, because the assemblages are taxonomically impoverished, the rest of the succession is considered to range down into the Upper and possibly Middle Jurassic. The composition of the Cretaceous assemblages suggests that the climate during this period was warm and semi-arid. A Xizang-Tarim Subprovince of the palynofloral North Gondwanan Province is tentatively identified in the north-east Tethyan region.

Biogeography of the Pistia Clade (Araceae): Based on Chloroplast and Mitochondrial DNA Sequences and Bayesian Divergence Time Inference

Pistia stratiotes (water lettuce) and Lemna (duckweeds) are the only free-floating aquatic Araceae. The geographic origin and phylogenetic placement of these unrelated aroids present long-standing problems because of their highly modified reproductive structures and wide geographical distributions. We sampled chloroplast (trnL-trnF and rpl20-rps12 spacers, trnL intron) and mitochondrial sequences (nad1 b/c intron) for all genera implicated as close relatives of Pistia by morphological, restriction site, and sequencing data, and present a hypothesis about its geographic origin based on the consensus of trees obtained from the combined data, using Bayesian, maximum likelihood, parsimony, and distance analyses. Of the 14 genera closest to Pistia, only Alocasia, Arisaema, and Typhonium are species-rich, and the latter two were studied previously, facilitating the choice of representatives that span the roots of these genera. Results indicate that Pistia and the Seychelles endemic Protarum sechellarum are the basalmost branches in a grade comprising the tribes Colocasieae (Ariopsis, Steudnera, Remusatia, Alocasia, Colocasia), Arisaemateae (Arisaema, Pinellia), and Areae (Arum, Biarum, Dracunculus, Eminium, Helicodiceros, Theriophonum, Typhonium). Unexpectedly, all Areae genera are embedded in Typhonium, which throws new light on the geographic history of Areae. A Bayesian analysis of divergence times that explores the effects of multiple fossil and geological calibration points indicates that the Pistia lineage is 90 to 76 million years (my) old. The oldest fossils of the Pistia clade, though not Pistia itself, are 45-my-old leaves from Germany; the closest outgroup, Peltandreae (comprising a few species in Florida, the Mediterranean, and Madagascar), is known from 60-my-old leaves from Europe, Kazakhstan, North Dakota, and Tennessee. Based on the geographic ranges of close relatives, Pistia likely originated in the Tethys region, with Protarum then surviving on the Seychelles, which became isolated from Madagascar and India in the Late Cretaceous (85 my ago). Pistia and Protarum provide striking examples of ancient lineages that appear to have survived in unique or isolated habitats.

Capitanian (Late Guadalupian, Permian) global brachiopod palaeobiogeography and latitudinal diversity pattern

A global database containing 3365 occurrences, 821 species and 251 genera of the Capitanian (Late Guadalupian, Permian) brachiopod faunas from 24 stations has been analyzed by cluster analysis using the Jaccard and Otsuka coefficients and the probabilistic index of similarity, nonmetric multidimensional scaling and minimum spanning tree. Two supergroups, three groups and six subgroups are revealed and interpreted as representing, respectively, two biotic realms (the Palaeoequatorial and Gondwanan Realms), two regions and six provinces. An additional realm (the Boreal Realm), based on the fauna from Spitsbergen, also appears recognizable although it also shows considerable similarities with southwestern North America and the northern margin of Gondwana as revealed by the statistical analysis. The Palaeoequatorial Realm can be further subdivided into the North America Region and the Asian Tethyan Region. The six biotic provinces are the Cathaysian Province in the Palaeotethys and Mesotethys, the Greenland-Svalbard Province in the Arctic region, the Austrazean Province in eastern Australia and New Zealand, the Grandian Province in western North America and the two transitional zones (the Himalayan Province in the southern temperate zone and the Sino–Mongolian–Japanese Province in the northern temperate zone). Polynomial regression analysis and rarefaction analysis indicate that the generic diversities of brachiopod faunas during the Capitanian peaked in the Palaeoequatorial Cathaysian Province and the two transitional zones (Himalayan Province and Sino–Mongolian–Japanese Province), but fell dramatically in the polar regions. The generic diversity of the Palaeoequatorial Grandian Province is apparently lower than in the two transitional zones of temperate palaeolatitudes, suggesting that the generic diversity of Capitanian brachiopod faunas does not exhibit a strict negative correlation with palaeolatitudes. This in turn would suggest that biogeographical determinants (such as geographical barriers, inhabitable area and ocean currents) other than latitude-related temperature control may also have played an important role in the dispersal of some brachiopods and the characterization of some local provinces and high diversities. The Capitanian global brachiopod palaeobiogeography is generally comparable with those in the Wuchiapingian and Changhsingian, but with some notable differences. These include: (1) that the Grandian Province of the Capitanian in western North America vanished after the end-Guadalupian regression, (2) that the western Tethyan Province of the Lopingian could not be distinguished in the Capitanian, and (3) that the Austrazean Province was larger in area than either in the Wuchiapingian or in the Changhsingian.

The Archipelagic Ocean System of the Eastern Eurasian Tethys

Abstract Unlike typical oceans such as the wide and “clean” Atlantic, the Tethys has been showing an archipelagic pattern during all its evolutionary stages. Compared with the traditional, wedge‐shaped and relatively “clean” ocean model, the archipelagic model is more suitable for the Tethys, especially the eastern Tethys. This paper demonstrates the eastern Tethys archipelagic system in terms of the subdivision, characteristics and evolutionary history of the Qinling‐Qilian‐Kunlun, South China and Xizang (Tibet)‐Yunnan Regions of the eastern Eurasian Tethys.

LATE CRETACEOUS PLANKTONIC FORAMINIFERAL BIOEVENTS IN THETETHYS AND IN THE SOUTHERN OCEAN RECORD: AN OVERVIEW

The Late Cretaceous planktonic foraminiferal distribution recorded at several drill sites (Deep Sea Drilling Project and Ocean Drilling Program) in the South Atlantic and south Indian Ocean and from sediment outcrops in the Tethyan region (Gubbio and El Kef) have been analyzed in order to investigate the presence of a similar sequence of bioevents occurring at low, middle, and high latitude. Comparative analysis highlights the co-occurrence of several bioevents; some of them are isochronous bioevents occurring in the Tethys and in the Southern Ocean record, whereas others are diachronous across latitudes but can be used for correlation at regional scale, as they show the same stratigraphic distribution in the South Atlantic and Indian Ocean record. Isochronous bioevents are the first and the last occurrence of Helvetoglobotruncana helvetica , and the first appearance of Falsotruncana maslakovae in the lower-middle Turonian. The first occurrence of Heterohelix papula in the Southern Ocean sites, correlated with the first occurrence of large heterohelicids in the Tethyan area, allows the Coniacian/Santonian boundary to be identified. The most reliable bioevents useful for correlation at a regional scale in the Southern Ocean record are the last occurrence of the marginotruncanids in the upper Santonian, the first and the last occurrence of Globigerinelloides impensus from the uppermost Santonian to upper Campanian, the first occurrence of Heterohelix rajagopalani in the middle-upper Campanian, and the appearance of Abathomphalus mayaroensis in the lower Maastrichtian.

PERMIAN FUSULINACEANS OF THE SURMAQ FORMATION IN THEABADEH REGION, CENTRAL IRAN

Fusulina ceans consisting of 56 species belonging to 30 genera are distinguished from the Surmaq Formation distributed in the Abadeh region, central Iran. Among them, 23 species, including three species newly proposed: Parafusulina tarazi, Skinnerella abadehensis , and Sphaerulina iranensis , are systematically described and discussed. Many microphotographs of fusulinaceans are illustrated so as to understand their wide intraspecific variation and to compare them with other faunas from the Tethyan regions. The Surmaq Formation is biostratigraphically divided into six zones from lower to upper: Darvasites ordinatus , Pseudofusulina quasifusuliniformis , Eopolydiexodina persica , Afghanella schencki , Neoschwagerina occidentalis , and Chusenella abichi . The first zone is probably Yakhtashian, the second is possibly Kubergandian, the third to fifth are Murgabian, and the last is Midian in age, based on the stratigraphic distribution and faunal correlation of neoschwagerinids and schwagerinids in Middle Permian formations of the Tethyan regions. Schwagerinids are dominant in these six zones, whereas almost all neoschwagerinids and verbeekinids are restricted to the fourth and fifth zones. Middle Permian fusulinacean faunas in South West Asian and Mediterranean Sea regions are well represented by those of the Surmaq Formation, and paleobiogeographically assignable to Province A (Western Tethyan Province). Fusulina cean faunas of Province A are largely different from those in Province B (Eastern Tethyan Province) by the very rare occurrence of typical Colania and Lepidolina , and from Province C (Panthalassan Province) by the presence of Afghanella and Sumatrina .

Planktonic foraminiferal zonation in the Cretaceous Yezo Group, Central Hokkaido, Japan

The mudstone of the Yezo Group exposed in Central Hokkaido yields abundant microfossils of calcareous nannofossils, foraminifers, radiolarians and dinoflagellates. Benthic foraminifers consisting of both agglutinated and calcareous species occur abundantly and consistently throughout the sequence, while specimens of planktonic foraminifers are generally fewer than benthics in all samples. We recognized the following 13 planktonic foraminiferal zones assigned to the late Aptian to early Campanian in the Oyubari and Haboro–Kotanbetsu areas; (1) Globigerinelloides spp., (2) Ticinella primula, (3) Biticinella breggiensis, (4) Rotalipora subicinensis– Rotalipora ticinensis, (5) Rotalipora appenninica, (6) Rotalipora globotruncanoides, (7) Rotalipora cushmani (8), Whiteinella archaeocretacea (9) Helvetoglobotruncana helvetica, (10) Marginotruncana pseudolinneiana, (11) Marginotruncana sinuosa, (12) Contusotruncana fornicata, (13) Globotruncana arca. The Globigerinelloides spp. to H. helvetica Zones (late Aptian to early Turonian) can be correlated with standard zones in the Tethyan regions, whereas the assemblages from the M. pseudolinneiana to G. arca zones lack tropical zonal markers of Dicarinella concavata, D. asymetrica and Globotruncanita elevata in many studied sections. The scarcity or lack of tropical zonal species during the late Turonian to early Campanian suggests that the Oyubari and Haboro–Kotanbetsu regions in Hokkaido were located in the Transitional to Boreal biogeographical provinces.

Takhtajan's floristic regions and foliicolous lichen biogeography: a compatibility analysis

Abstract:Takhtajan's floristic regions of the world, based on vascular plant distribution, were used for a comparative analysis of foliicolous lichen biogeography. Of the 35 regions distinguished by that author, 23 feature foliicolous lichens. The South-East African, Fijian, Polynesian and Hawaiian regions lack sufficient information and were excluded from further analysis. Using multi-dimensional scaling and cluster and cladistic analyses, the remaining 19 regions were grouped into six lichenogeographical regions: (1) Neotropics, (2) African Paleotropics (including Madagascar, Réunion and Seychelles), (3) Eastern Paleotropics (including North-East Australia and New Caledonia), (4) Valdivian region (temperate rainforest in southern South America), (5) Tethyan region (subtropical areas of Macaronesia, Mediterranean, and Western Irano-Turanian) and (6) Neozealandic-Tasmanian region (temperate rainforests of New Zealand and Tasmania). Affinities between these six large scale regions, with 57–77% shared species, are still stronger than those between the 35 smaller scale regions defined by Takhtajan [(20–)40–60(–75)% shared species]. Based on presence/absence within each of the six regions, 22 potential distribution patterns were defined for foliicolous lichens. Many species are widely distributed; 21% are cosmopolitan or pantropical, while 19% are disjunct on at least two continents, and only 60% are restricted to one of the three major tropical areas (nearly 100% in vascular plants). Most of the latter are found in the Neotropics, while the African Paleotropics are poor in endemics. Most genera deviate significantly from overall distribution patterns; for example, Strigula and Calopadia have higher proportions of widely distributed species, while Porina displays a concentration of Eastern Paleotropical endemics. Species diversity and composition of the six regions indicate that the three extra-tropical foliicolous lichen biotas (Valdivian, Tethyan, Neozealandic-Tasmanian) are the result of partly separate evolutionary histories. On the other hand, there is a strong affinity between the Neotropics and the African Paleotropics, suggesting a shared Western Gondwanan element in the foliicolous lichen biotas of these two regions.

Calcareous nannofossil biostratigraphy and paleoecology of the Cretaceous–Tertiary transition in the central eastern desert of Egypt

The Gebel Qreiya and nearby Wadi Hamama sections of the central Eastern Desert are among the most complete K/T boundary sequences known from Egypt. The two sections were analyzed spanning an interval from l.83 Myr below to about 3 Myr above the K/T boundary. A 1-cm-thick red clay layer at the K/T boundary at Gebel Qreiya contains an Ir anomaly of 5.4 ppb. The high-resolution study and well-preserved nannoflora provide good age control and the first quantitative records of calcareous nannofossil assemblages for paleoecological interpretations across the K/T transition in Egypt. Four zones ( Micula murus, Micula prinsii, NP1, and NP2) were distinguished and correlated with other nannofossil and planktonic foraminiferal zonations that are broadly applicable for the eastern Tethys region. Latest Maastrichtian assemblages are abundant and diverse, though Cretaceous species richness progressively decreased across the K/T boundary. Dominant species include Arkhangelskiella cymbiformis, Micula decussata and Watznaueria barnesae, with high abundance of dissolution-resistant M. decussata reflecting periods of high environmental stress. Thoracosphaera blooms mark the K/T boundary and are followed by an acme of the opportunistic survivor Braarudosphaera bigelowii, the first appearance of the new Tertiary species Cruciplacolithus primus, and an acme of Coccolithus cavus/ pelagicus. These successive abundance peaks provide the basis for subdivision of the Early Danian Zones NP1 and NP2 into five subzones. Correlation of selected nannofossil taxa from the Egyptian sections with those from various onshore marine and deep-sea sections provides insights into their paleoenvironmental and paleoecological affinities.

Overview of the genesis and emplacement of Mesozoic ophiolites in the Eastern Mediterranean Tethyan region

The Eastern Mediterranean region exhibits a fascinating diversity of ophiolites and related oceanic magmatic units of mainly Triassic, Jurassic and Cretaceous age. Comparisons with the settings of modern oceanic lithosphere indicate that the various Eastern Mediterranean ophiolites have different origins and formed in a variety of tectonic settings. Some have argued that the largest ophiolites, of Jurassic and Cretaceous age (e.g. Troodos), formed at mid-ocean ridges. However, the widespread occurrence of andesitic extrusives, chemically “depleted” basalts and highly magnesian lavas (boninites), favour formation of most of the large, relatively intact ophiolites in the Eastern Mediterranean region above subduction zones rather than at mid-ocean ridges (MORs). Such ophiolites probably formed by spreading during the initial stages of intra-oceanic subduction, prior to the emergence of any major related oceanic arc. Supra-subduction-type ophiolites typically formed during short-lived periods (<5 Ma) of regional plate re-organisation. By contrast, most MOR-type oceanic crust was subducted, or is preserved only as dismembered thrust sheets or blocks in ophiolitic melange, commonly metamorphosed under high-pressure/low-temperature (HP/LT) conditions. However, MOR-type ophiolites are locally preserved (e.g. Jurassic Western-type Albanian ophiolite). Seamounts were preferentially accreted into melanges and record subduction of large areas of oceanic crust. Volcanic–sedimentary units of mainly Triassic age, including alkaline to MOR-type extrusives and radiolarites record rifting, transitional to spreading of Neotethyan ocean basins. Back-arc, intra-continental marginal basins of Triassic and Late Jurassic age developed within the northerly (Eurasian) continental margin (e.g. Jurassic Guevgueli ophiolite, N Greece). Ophiolites formed in these basins were exposed by uplift, without significant transport. Transform-influenced ophiolites are occasionally preserved (e.g. Late Cretaceous Tekirova ophiolite, SW Turkey). Metamorphic soles reflect tectonic displacement of oceanic lithosphere while still hot, near a spreading centre (whether of mid-ocean ridge or supra-subduction type). The Eastern Mediterranean subduction-type ophiolites, of both Jurassic and Cretaceous age, were rooted in several coeval Neotethyan oceanic basins, separated by microcontinents and cannot be interpreted as vast, far traveled thrust sheets derived (at different times) from a single, palaeogeographically simple Tethyan oceanic basin.

Middle to Late Jurassic bivalves of the genera Neocrassina and Trigonopis from New Zealand

Bivalves of the genera Neocrassina and Trigonopis are described from the Middle‐Late Jurassic of New Zealand. Neocrassina is represented by three new species. The new subfamily Trigonopinae is introduced to accommodate the genus Trigonopis, which was previously classed as a subgenus of Opis. Trigonopis is represented by one previously described species and one new species. Paleobiogeography is analysed in terms of the global distribution of Neocrassina and Trigonopis. Neocrassina was present in most regions of the Boreal and Tethyan realms. In New Zealand, it is first recorded from rocks of Early Temaikan age (Aalenian‐Bajocian). The distribution of Trigonopis shows that this genus was common in European Tethyan regions, but sparsely distributed elsewhere. A comparison of New Zealand species, with forms from other regions, demonstrates that Trigonopis most likely migrated to the Jurassic southern ocean, by way of the temporary seaway connecting the Tethys Sea with the Bay of Antarctica, during the Callovian marine transgression.

Palaeoenvironmental setting of rudists in the Upper Cretaceous (Turonian–Maastrichtian) Adriatic Carbonate Platform (Croatia), based on sequence stratigraphy

Rudist bivalves are abundant in Upper Cretaceous Adriatic carbonate platform deposits in biostromes of varying biodiversity and density that alternate with foraminiferal wackestones to packstones. Their distribution is reviewed with respect to the sequence stratigraphic framework. The Turonian–Senonian succession of the platform comprises three third order sequences: (1) Turonian–Middle Santonian; (2) Middle Santonian–Upper Campanian; (3) Upper Campanian–Upper Maastrichtian. After the early Turonian transgression, which is recorded in all areas investigated, the Adriatic carbonate platform had a regionally varied history. Our analysis shows that hippuritid individuals here grew preferentially in relatively open, outer shelf conditions that prevailed while carbonate production was catching up with sea-level rise following platform foundering. By contrast, densely packed and laterally extensive radiolitid clusters formed in more restricted platform settings where carbonate production tended to keep up with relative sea-level rise and yielded successive shallowing-upward cycles. This pattern contrasts with that known from more northern Tethyan regions (such as the Pyrenees and SE France), where hippuritids frequently dominate the restricted platform top deposits. The difference may reflect a greater tendency to hypersalinity on the broad interiors of the pure carbonate platforms in central and southern Tethyan regions, though other possible explanations have been offered.

Circum-Mediterranean Oligo–Miocene biogeographic evolution – the gastropods’ point of view

Based on studies in Iran (Qom Basin, Esfahan–Sirjan Basin, Zagros Mountains), in Turkey (Mut and Sivas basins), in the Mesohellenic Basin, and in northeastern Egypt, a new palaeobiogeographic concept for the Oligocene and Miocene in the circum-Mediterranean area with special emphasis on the distribution patterns of gastropod faunas is presented. A very strict biogeographic terminology is proposed to avoid the common fusion of geographic, faunistic and geodynamic terms in the palaeontologists’ jargon. Our main interest focuses on the affinities and the faunistic interactions between the early ‘Mediterranean’ and the early ‘Indo-Pacific’ regions during the Oligo–Miocene. Especially the role of the early Indo-Pacific faunas as the mythic centre of origination of Early Neogene European mollusc faunas, as often vaguely indicated in the literature, is critically evaluated. This leads to the establishment of a Mediterranean–Iranian Province and a Western Indian–Eastern African Province as palaeobiogeographic subunits of the Western Tethys Region during the Oligocene. Due to major geodynamic and related biogeographic changes in the Early Miocene the Western Tethys Region no longer existed and was replaced by the Proto-Mediterranean–Atlantic Region. For the area of the Paratethys the palaeobiogeographic unit Danubian Province, which includes the Proto-Caspian Subprovince, is proposed. Furthermore, the underrated transatlantic communication of the Oligo–Miocene nearshore mollusc faunas is demonstrated. Altogether this paper is a contribution to the discussion on the biogeographic concepts, classification and nomenclature in palaeontology as initiated by Westermann [Palaeogeogr. Palaeoclimatol. Palaeobiogeogr. 158 (2000) 1–13; 163 (2000) 49–68].

Late Cretaceous to early Paleocene climate and sea-level fluctuations: the Tunisian record

Climate and sea-level fluctuations across the Cretaceous–Tertiary (K–T) transition in Tunisia were examined based on bulk rock and clay mineralogies, biostratigraphy and lithology in five sections (El Melah, El Kef, Elles, Ain Settara and Seldja) spanning from open marine to shallow inner neritic environments. Late Campanian to early Danian trends examined at El Kef and Elles indicate an increasingly more humid climate associated with sea-level fluctuations and increased detrital influx that culminates at the K–T transition. This long-term trend in increasing humidity and runoff in the Tethys region is associated with middle and high latitude cooling. Results of short-term changes across the K–T transition indicate a sea-level lowstand in the latest Maastrichtian about 25–100 ka below the K–T boundary with the regression marked by increased detrital influx at El Kef and Elles and a short hiatus at Ain Settara. A rising sea-level at the end of the Maastrichtian is expressed at Elles and El Kef by deposition of a foraminiferal packstone. A flooding surface and condensed sedimentation mark the K–T boundary clay which is rich in terrestrial organic matter. The P0–P1a transition is marked by a sea-level lowstand corresponding to a short hiatus at Ain Settara where most of P0 is missing and a period of non-deposition and erosion in the lower part of P1a (64.95 Ma). At Seldja, P0 and possibly the topmost part of CF1 are missing. These sea-level fluctuations are associated with maximum humidity. These data suggest that in Tunisia, long-term environmental stresses during the last 500 ka before the K–T boundary and continuing into the early Danian are primarily related to climate and sea-level fluctuations. Within this long-term climatic trend the pronounced warm and humid event within the latest Maastrichtian Zone CF1 may be linked to greenhouse conditions induced by Deccan volcanism. The absence of any significant clay mineral variations at or near the K–T boundary and Ir anomaly suggests that the bolide impact had a relatively incidental short-term effect on climate in the Tethys region.

New Eocene Decapods (Thalassinidea and Brachyura) from Southern California

A new decapod fauna has been recovered from Eocene rocks of San Diego County, California. Decapod faunas of Eocene age have been rare from California, although they are well described from the northern Pacific coast. Three new species, including Neocallichirus rhinos, Ctenocheles secretanae, and Minohellenus inexpressus, and two new genera and species, Acanthoportunus buchanani and Vegarthron santiago, are reported from this new fauna. A new genus has been erected to accommodate Portunites triangulum and Portunites granulifer; both are herein referred to Maeandricampus, new genus. Callianassa matsoni Rathbun has been reassigned to Neocallichirus. Portions of the cephalothorax and abdomen of a species of Ctenocheles are described from fossils for the first time. Orbitoplax weaveri, previously known from Eocene rocks of California and Oregon, is reported from the Eocene Mission Valley Formation and the Ardath Shale for the first time. In addition, one specimen of a stomatopod of indeterminate genus is noted. The Eocene decapod fauna from California, now containing eighteen genera, has elements common to the northern Pacific coast of North America as well as taxa known only from California; thus, the area appears to have been suited for decapods adapted to a wide variety of temperature and other environmental conditions. Several genera appear to have evolved within the region, whereas others may have been introduced from the Atlantic or Tethys region via the Central American Seaway. The number of Pacific amphitropical genera continues to increase; two portunid genera discussed here display such a pattern, adding to the four already reported for Cretaceous and Tertiary rocks of the region.