Early Paleocene Age Research Articles

Eudaemonema webbi sp. nov. (Mammalia, Mixodectidae) from the late Paleocene of western Canada: the youngest known mixodectid

Mixodectidae (Mammalia, Archonta) are an unusual, poorly known family of dermopteran-like mammals that have been discovered at several North American localities of primarily early Paleocene age. Among the three or four recognized mixodectid genera, Eudaemonema Simpson is perhaps one of the least understood, being known from only a few localities of late Torrejonian and earliest Tiffanian age. This paper reports on a new species of Eudaemonema from the late Paleocene of Alberta, Canada, that significantly extends the geographic and stratigraphic ranges of the genus. Eudaemonema webbi sp. nov. is known from middle and late Tiffanian localities in central and south central Alberta, and it represents the youngest and northernmost species of Eudaemonema so far discovered. E. webbi differs from the genotypic species E. cuspidata in being larger and in having a suite of dental characters (e.g., molariform posterior premolars, enlarged molar protocone and hypocone, development of a second grinding platform on the lower molars) that suggests an increased emphasis on grinding during mastication. E. webbi possesses several dental features (e.g., broad, shelf-like molar paraconid–paracristid, lingually shifted molar hypoconulid) that resemble those of cynocephalids (Mammalia, Dermoptera), with these resemblances interpreted herein as convergent. The occurrence of E. webbi at Gao Mine extends the stratigraphic range of Eudaemonema into the late Tiffanian (Ti5) and represents the youngest known record of Mixodectidae.

Lower jaw of the Early Paleocene mammalAlveugenaand its interpretation as a transitional fossil

The Paleogene Order Taeniodonta Cope, 1876—peculiar heavy-bodied mammals, some with evergrowing cheek teeth—are grouped with the Late Cretaceous eutherianCimolestesMarsh, 1889, along with a host of other taxa in a superordinal group, the Cimolesta. Taeniodonts were thought to have arisen fromCimolestesindirectly, through PaleoceneProcerberusSloan and Van Valen, 1965. The recently described PaleoceneAlveugenaEberle, 1999, until now known only from the upper dentition, has been put forth as a transitional form between cimolestids and taeniodonts on phylogenetic and biostratigraphic grounds. An older taeniodont, the Late CretaceousSchowalteriaFox and Naylor, 2003, has since been described, complicating taeniodont origins. We describe here a lower jaw that we refer toAlveugenafrom the lower part of the Ludlow Member of the Fort Union Formation in North Dakota. The lower jaw comes from strata of early Early Paleocene age (Puercan 1 North American Land Mammal Age) ~8.5 m above a Cretaceous-Paleogene boundary, identified using palynological criteria. A cladistic analysis is here presented using new data onSchowalteriaandAlveugena, added to that ofCimolestes, Procerberus formicarumSloan and Van Valen, 1965,P. grandisMiddleton and Dewar, 2004, andOnychodectes.This analysis revealedAlveugenaas the sister taxon of the taeniodonts but with a closer relationship toCimolestesthanProcerberus, suggesting that taeniodonts evolved from aCimolestes-like ancestor. We discuss the age relations of early taeniodonts and related taxa and propose a scenario of ancestor-descendent relations that minimizes, but does not eliminate, implied stratigraphic gaps.

New cyriacotheriid pantodonts (Mammalia, Pantodonta) from the Paleocene of Alberta, Canada, and the relationships of Cyriacotheriidae

Cyriacotheriidae are a family of unusual small-bodied pantodonts known from the Paleocene of the Western Interior of North America. Cyriacotheriids possess a suite of dental characters similar to that of pantodonts (e.g., molar dilambdodonty, lingual molar hypoconulids), as well as several divergent features (e.g., molarized premolars, strong molar conules) that have been interpreted as “dermopteran-like.” the unusual combination of pantodont and dermopteran-like characters, combined with a limited fossil record, has made attempts at understanding the broader relationships of Cyriacotheriidae difficult. This paper reports on a new genus and two new species of cyriacotheriids from the Paleocene of Alberta, Canada, with both species significantly older than those of the only previously described cyriacotheriid, Cyriacotherium. Collectively, the dentitions of these new taxa exhibit derived characters seen in Cyriacotherium (e.g., robust molar conules, strong molar dilambdodonty) in addition to a number of plesiomorphies seen in more basal pantodonts (e.g., conspicuous molar entoconids, deep premolar ectoflexus) and, importantly, posterior premolars that are weakly molariform and non-dilambdodont. A phylogenetic analysis of the new cyriacotheriid, basal pantodonts, dermopterans, and dermopteran-like eutherians resulted in Cyriacotheriidae nesting within a monophyletic Pantodonta. the results strengthen previous hypotheses regarding the pantodont affinities of the family, and suggest that the dermopteran-like features seen in the more derived Cyriacotherium were acquired convergently. Although the discovery of new cyriacotheriids sheds light on the evolutionary history of the family, it cannot resolve the ongoing questions of pantodont origins; nonetheless, their discovery in strata of early Paleocene age indicates that significant parts of the evolutionary history of Cyriacotheriidae, and North American pantodonts more generally, have yet to be discovered.

EARLY DANIAN PLANKTIC FORAMINIFERA FROM CRETACEOUS-TERTIARY INTERTRAPPEAN BEDS AT JHILMILI, CHHINDWARA DISTRICT, MADHYA PRADESH, INDIA

The main Deccan volcanic province erupted mainly in terrestrial to lacustrine environments of late Maastrichtian to early Paleocene age, and lack age diagnostic fossils to accurately place the Cretaceous-Tertiary (K-T) boundary. As a result, the precise position of the K-T event within the volcanic province has remained speculative, and no realistic assessment of the biotic consequences of Deccan volcanism at K-T time has been possible. Here, we report the discovery of early Danian Zone P1a planktic foraminifera within lacustrine to brackish-marine ostracod assemblages near Jhilmili, Chhindwara District, India. These foraminiferal assemblages identify the K-T boundary in intertrappean sediments bracketed by basalt traps that are regionally correlative with C29R (Ambenali Formation) and the C29R-C29N transition (Mahalabeshwar Formation). The Jhilmili sequence is thus correlative with the shallow-marine, intertrappean Zone P1a assemblage and C29R and C29N of the lower and upper basalt traps exposed in Rajahmundry quarries. The presence of planktic foraminifera in predominantly terrestrial intertrappean sediments some 800 km from the nearest ocean suggests the presence of a seaway along the Narmada and Tapti rift zones with Jhilmili located at the eastern margin.

Patterns of mammalian evolution across the Cretaceous-Tertiary boundary

The available fossil record of mammalian evolution across the Cretaceous-Tertiary (K-T) boundary is highly biased biogeographically by the results of detailed sampling of Late Cretaceous and Paleocene local faunas in what is now the Western Interior of the North American continent. In this area, which was then a coastal lowland, the mass extinction marking the K-T boundary resulted in extinction of many mammalian lineages. Analysis of the phylogenetic relationships of the mammals comprising North American early Paleocene faunas demonstrates that recovery of taxonomic diversity after the K-T boundary was the product of two processes: 1) evolutionary radiation of some locally surviving stocks and 2) immigration of mammals from other, as yet unsampled areas. Limited evidence suggests that dispersal of the groups that dominate these earliest Paleocene faunas had begun in the latest Cretaceous. Some mammalian local faunas of Late Cretaceous or early Paleocene age are known from other continents, but none of these provide as complete a fossil record of mammalian evolution during this interval. In spite of these limitations, analysis of the available, global fossil record reveals significant biogeographic provinciality of mammalian faunas and some similarities in their patterns of extinction and recovery of taxonomic diversity during the transition from the Cretaceous into the Tertiary.

“Calc-alkaline” magmatism of the Omgon Range: Evidence for Early Paleogene extension in the western Kamchatka segment of the Eurasian continental margin

T he hypabyssal rocks of the Omgon Range, western Kamchatka, that intrude Upper Albian-Lower Campanian deposits of the Eurasian continental margin belong to three coeval (62.5-63.0 Ma) associations: (1) ilmenite gabbro-dolerites, (2) titanomagnetite gabbro-dolerites and quartz microdiorites, and (3) porphyritic biotite granites and granite-aplites. The Early Paleocene age of the ilmenite gabbro-dolerites and biotite granites was confirmed by zircon and apatite fission-track dating. The ilmenite and titanomagnetite gabbro-dolerites were produced by the multilevel fractional crystallization of basaltic melts with, respectively, moderate and high Fe-Ti contents and the contamination of these melts with rhyolitic melts of different compositions. The moderate- and high-Fe-Ti basaltic melts were derived from mantle spinel peridotite variably depleted and metasomatized by slab-derived fluid prior to melting. The melts were generated at variable depths and different degrees of melting. The biotite granites and granite aplites were produced by the combined fractional crystal- lization of a crustal rhyolitic melt and its contamination with terrigenous rocks of the Omgon Group. The rhy- olitic melts were likely derived from metabasaltic rocks of suprasubduction nature. The Early Paleocene hypabyssal rocks of the Omgon Range were demonstrated to have been formed in an extensional environment, which dominated in the margin of the Eurasian continent from the Late Cretaceous throughout the Early Pale- ocene. Extension in the Western Kamchatka segment preceded the origin of the Western Koryakian-Kamchatka (Kinkil') continental-margin volcanic belt in Eocene time. This research was conducted based on original geo- logical, mineralogical, geochemical, and isotopic (Rb-Sr) data obtained by the authors for the rocks.

Geochemistry of the Fluids Related to Epigenetic Carbonate-Hosted Zn-Pb Deposits in the Maestrat Basin, Eastern Spain: Fluid Inclusion and Isotope (Cl, C, O, S, Sr) Evidence

Epigenetic Zn-Pb deposits in the Maestrat basin (eastern Spain) are hosted by dolostones that replace Aptian limestones. The deposits have morphologies ranging from mineralized breccias to stratiform, massive replacements. Sphalerite and galena cementing breccias precipitated as well-formed crystals; whereas, the stratiform replacements are characterized by textures such as colloform and skeletal or dendritic growths. Two mineralized areas are found: Valdelinares and Mas de la Mina-Cedraman. The highest ore grades (up to 11% Zn) and largest deposits (ca. 30,000 t of sulfides) occur as stratiform deposits in the Valdelinares area (Resurreccion and Restauracion mines). In the Valdelinares area, microthermometry of fluid inclusions reveals that ore-stage minerals precipitated by the mixing of two distinct fluids: fluid A, a high salinity brine, with salinity greater than 26 wt percent NaCl equiv and temperatures above120oC, and fluid B, a low salinity fluid, with less than 15 wt % NaCl equiv and temperatures around 40oC. Fluid A-dominated brines are found in mineralized breccias located in the vicinity of major fracture zones; whereas, more dilute fluids are typical of massive ores. In the Mas de la Mina area, the presence of two fluids is less evident, although the ranges in both temperature and salinity also point to mixing. Na-K-Li-Cl-Br systematics of the inclusion fluids indicates that fluids A and B were evaporated seawater that did not significantly interact with K- and Li-rich sediments. The most diluted mixtures (fluid B) are characterized by relatively heavy Cl (δ 37 Cl = 1.11 and 1.19‰) compared to fluid-A dominated brines, which have δ 37 Cl values close to seawater (0‰). The sulfur isotope compositions range from ‐10.5 to 13.4 per mil for sulfides and between 16 and 17.8 per mil for barite. Such values are consistent with mixing of a metal-rich brine with small amounts of 32 S-enriched sulfur and a sulfur-rich fluid with a δ 34 S close to the marine sulfate of Late Cretaceous to early Paleocene age. The C and O isotope compositions of ore-stage calcite (δ 13 C from 0.6 to ‐7.8‰; δ 18 O from 17.2 to 20.9‰) are also explained by the precipitation from different mixtures of fluids A and B. From the geochemical data, it is inferred that fluid mixing played a key role in the formation of the Zn-Pb deposits in the Maestrat basin. Ore precipitation occurred in places where brines ascending through faults interacted with a dilute, sulfur-rich fluid. Deposits with the highest ore grade and size are related to areas where the most extensive mixing occurred.

Paleobiogeography of late Early Cretaceous to Early Paleocene marine Ostracoda in Arabia and North to Equatorial Africa

About 1270 marine ostracod species of Aptian to Early Paleocene age from Central, West, North and East Africa (inclusive Madagascar) as well as the Arabian Peninsula and Pakistan/Western India have been examined on their spatial and stratigraphical distribution. Their paleobiogeographical relations have been examined based on the Jaccard-index. The results of these comparative studies are demonstrated on nine geographical maps for each stage (Aptian through Early Paleocene) and four paleogeographical reconstructions including the assumed land/sea distribution for Cenomanian, Turonian, Maastrichtian, and Early Paleocene times. The major results are the recognition of an increasingly uniform pan-‘South Tethyan ostracod province’ (North and Northeast Africa and the Arabian Peninsula) from the Aptian to the Cenomanian. Due to the emergence of major parts of the Arabian Shield during the Turonian, this pan-South Tethyan bioprovince was split into a western ‘ Protobuntonia numidica ostracod province’ (North Africa and Western Middle East) and an eastern ‘ Kaesleria ostracod province’ (Eastern Arabia, South Iran, Somalia) since the Coniacian. While the proliferation of the phylogenetic lines of the ostracod genera and species of the ‘South Tethyan ostracod province’ towards the Protobuntonia numidica faunas into the Turonian–Coniacian was continuous, the newly developing genera and species of the Protobuntonia numidica and the Kaesleria provinces of the ‘Senonian’–Early Paleocene had almost nothing in common. Although most of Northeast Africa and the Arabian Shield underwent strong subsidence during the Campanian–Maastrichtian combined with a widespread transgression, these strictly separated bioprovinces did not reunite or show clear faunal interrelationships during these times. The reasons for the described phenomena are probably largely to be sought in the paleoecological peculiarities of the regarded ostracod faunas (i.e. a relatively cooler water fauna in the Protobuntonia province (probably partially influence by upwelling) and a relatively warmer, tropical fauna in the Kaesleria province). However, the strict separation of these ostracod assemblages along a narrow N–S directed borderline running from Northeast Saudi Arabia across Jordan into Syria is thought to be highly unusual and to require further investigation, which could probably stimulate new paleo-oceanographical and paleogeographical considerations for the Late Cretaceous–Early Paleocene of Northeast Africa, the Middle East and Arabia.

Paleoenvironmental and tectonic changes across the Cretaceous/Tertiary boundary at Tora, southeast Wairarapa, New Zealand: A link between Marlborough and Hawke's Bay

The Late Cretaceous‐Paleocene succession exposed on the Tora coast, near the southeastern tip of the North Island, is distinguished by an unusual lithofacies of the Whangai Formation, and by an apparently unique formation, Manurewa Formation, which spans the Cretaceous/Tertiary (K/T) boundary. The Late Cretaceous siliceous Whangai Formation at Tora includes zones of slumps and olistostromes, containing megaclasts of limestone up to 3 m long. The olistostromal deposits suggest steep submarine topography with a high rate of erosion, and imply tectonic activity. The common occurrence of hummocky cross‐stratification suggests deposition in shelf depths above storm wave base. The sharply overlying Manurewa Formation is interpreted as the infill of a major shallow channel complex, perhaps >9 km wide and spanning the K/T boundary in time. The older of two channelled units is of latest Cretaceous (latest Haumurian/late Maastrichtian) age, and consists of bioturbated alternating thin sandstone and mudstone with thin conglomerate lenses and limestone beds. It is likely to have been deposited in a low‐energy environment, probably deeper than that of the Whangai. The younger channel system, of early Paleocene (early Teurian) age, erodes into the older in the northeast, and into the underlying Whangai Formation in the southwest. Basal deposits consist predominantly of medium to coarse, thick‐bedded, glauconitic sandstone, with local low‐angle cross‐stratification and microflora typical of low salinity conditions, suggesting deposition in shallow shelf depths. These deposits contain olistrostromes with megaclasts up to 1 m long of limestone and rarer dark grey siltstone or very fine sandstone clasts typical of Whangai Formation. The inclusion of megaclasts of Whangai Formation indicates that local emergence and erosion of older strata was occurring. Deposits grade upward into well‐sorted bioturbated sandstones of the Awhea Formation, with prominent low‐angle cross‐stratification, interpreted as very shallow marine, probably nearshore deposits. The channel system represented by the Manurewa Formation records an initial relative sea‐level rise, followed by an abrupt sea‐level fall at, or close to, the K/T boundary. New Zealand was in a passive margin tectonic setting at the time, but the widespread presence of olistostromes, some including clasts derived from older strata, suggest that local tectonic activity and uplift was occurring. The effects may have been enhanced by a climatic shift in storm tracks and intensity in the latest Cretaceous, which is supported by the evidence of strong wave activity. By contrast, to the south in Marlborough, the K/T boundary succession is commonly characterised by an apparently conformable lithologic change from limestone to chert, although with local hiatus. To the north, in southern Hawke's Bay, the coeval succession is characterised by a disconformity separating greensand from underlying light grey, slightly calcareous mudstone of the Whangai Formation. The Tora sequence may provide the link between two distinctly different lithologic successions.

Danian Normapolles from the conglomeratic formation near Panagyurishte and Strelcha (Sredna Gora Mountains, Bulgaria)

The paper presents description and illustrations of 10 Normapolles species obtained from the conglomeratic formation near Panagyurishte and Strelcha and new for the Bulgarian palynoflora. They belong mainly to the genera Nudopollis, Oculopollis, Semioculopollis and Interporopollenites. The taxa are considered to be stratigraphically important. Their concurrent ranges and correlation to the already known assemblages of the same age in the Normapolles province suggests a latest Maastrichtian to early Paleocene (most probably Danian) age for the conglomeratic formation.

Paleocene sub-basaltic sediments on Savoia Halvø, East Greenland

Field work by the Geological Survey of Denmark and Greenland (GEUS) on Savoia Halvø, central East Greenland in 2001 (see also Larsen et al. 2002, this volume) included a study of sediments underlying the Palaeogene basalts on the south coast of Scoresby Sund (Fig. 1). The importance of this small exposure is based on the fact that it provides one of the few opportunities for establishing a marine biostratigraphic date for the sediments below the basalts. Dinoflagellate cysts from the sediments provide a maximum Early Paleocene age for the onset of the volcanism in central East Greenland. Reports from previous field work have mentioned the sediments (Hassan 1953; Birkenmajer 1972), but no precise age assignment was presented due to the absence of diagnostic fossils. The sub-volcanic sediments of Savoia Halvø represent the youngest preserved marine sedimentary deposits of the Upper Palaeozoic – Cenozoic rift-basins onshore East Greenland. The overlying Palaeogene flood basalts occasionally contain very thin sedimentary beds between the lava flows, but these were deposited above sea level. Neogene uplift of the East Greenland margin brought a definitive end to accumulation in the old sedimentary basins (Watt et al. 1986; Christiansen et al. 1992).

Rates of volcanic deposition, facies changes and movements in a dynamic basin: the Nuussuaq Basin, West Greenland, around the C27n-C26r transition

Abstract The initial stages of Palaeogene volcanism in the Nuussuaq Basin in West Greenland were characterized by eruption of basaltic and picritic magmas through sediments of Cretaceous to early Paleocene age into a marine or lowlying coastal environment. Recent magnetostratigraphic work has recognized the C27n-C26r transition (estimated duration less than 10 ka and here assumed to be 5 ka) as a c. 170 m thick zone within a succession of thin picritic lava flows. Multimodel photogrammetry combined with chemical and lithological analysis of the volcanic rocks has allowed detailed 3D analysis of the facies variation within this narrow time window. Subaerial lavas flowed eastwards over a more than 40 km wide front. On northern Disko they covered an existing lava plateau and buried a subaerial landscape of dipping Cretaceous sandstones, while on Nuussuaq they flowed into an up to 700 m deep marine embayment and formed prograding hyaloclastite fans passing into fine-clastic mass flows. With a progradation rate of 0.5–1 m a −1 the palaeogeography of the basin changed considerably during the short time interval. In addition to substantial basin subsidence, the volcanic facies changes have also preserved a record of synvolcanic differential movement of extensional fault blocks. The following parameters are estimated for the volcanism within the Nuussuaq Basin during the C27n-C26r transition: Production rate c. 0.042 km 3 a −1 , productivity c. 1.2 × 10 −3 km 3 a −1 km −1 (rift), volcanic aggradation c. 33 m ka −1 , subsidence c. 25 m ka −1 . If the volcanism evolved continuously at this high aggradation rate, all of the Vaigat Formation could have erupted in 70 ka. However, the complex geological record indicates a much longer total duration, and the volcanism must have had an intermittent character.

A summary of the geology of the Iranian Makran

Abstract The Iranian Makran has been entirely mapped geologically on a scale of 1:250 000, except for a narrow coastal strip, which exposes the very youngest Cenozoic sediments of the main Makran accretionary prism. The geology of the Makran is less widely known than the geology of Oman, because it has been published in detail only in reports of the Geological Survey of Iran. There is no extension of the geological formations of Oman into the Makran, the only extension of Oman ophiolitic formations into Iran being at Neyriz and Kermanshahr, hundreds of kilometres to the NW. This summary is based on field mapping, photo-interpretation being used only to connect traverse lines. The oldest rocks are metamorphic rocks, which form the basement to the Bajgan-Dur-kan microcontinental ‘sliver’, a narrow block that extends hundreds of kilometres from the Bitlis Massif in Turkey, through the Sanandaj-Sirjan Block of the Zagros, to north of Nikshahr in the east of the Makran. Other metamorphic rocks form the Deyader Complex near Fannuj on the southern margin of the Jaz Murian Depression. These include blueschists, and are thought to form the tip of the Tabas Microcontinental Block, largely exposed north of the depression. There is also a small microcontinental block to the east, the Birk Block, which exposes only Cretaceous platform limestones and Permian sediments. The Bajgan Metamorphic Series are overlain, with a tectonized unconformable contact, by highly deformed and disrupted platform carbonates of Early Cretaceous to Early Paleocene age (Dur-kan Complex), containing tectonic inliers of Carboniferous, Permian and, rarely, Jurassic age. Ophiolites occur in two structural positions. South of the Bajgan-Dur-kan Block, the tectonic Coloured Mélange of the Zagros continues eastwards inland of the Bashakerd Fault; this includes two layered ultramafic complexes, one with chromities. The blocks forming the mélange include radiolarites and deep-water limestones of Jurassic to Early Paleocene age. Ophiolites developed north of the microcontinental block form three distinct igneous complexes, two layered and one with intermediate sheeted dykes. Intercalated in the volcanic rocks of these ophiolites are radiolarites and deep-water limestones ranging in age from Jurassic to Paleocene time. There are small developments of Cretaceous sediments carrying rudists in the extreme NW of the inner ophiolite tract. In the NE, ophiolites are developed in the Talkhab Mélange. All these ophiolites represent former, largely Cretaceous, tracts of deep ocean. The Cenozoic rocks form two immense accretionary prisms. The main Makran prism includes Eocene-Oligocene and Oligocene-Miocene flysch turbidite sequences, estimated as individually >10 000 m thick. Above these sequences, there is an abrupt passage up without any apparent unconformity, through reefal Burdigalian limestones, and locally a harzburgite conglomerate development, into neritic sequences with minor turbidites, extending into the Pliocene units. The Saravan accretionary prism to the east repeats tectonically three thick flysch turbidite sequences of Eocene-Oligocene age, but younger sediments are restricted here to minor Oligocene-Miocene conglomerates, unconformable on the above sequences. There is a line of Oligocene(?) granodiorite bodies within the Saravan accretionary prism. Intense folding and development of schuppen structure, dislocation and mélanging of the sediments affected the entire region in Late Miocene-Early Pliocene time. Post-tectonic uplift was followed by scattered developments of fanglomerates beneath the fault scarps. The Neogene deformation has obscured earlier deformational events. There is unconformity beneath Eocene sediments representing a mid-Paleocene disturbance. There is also evidence of a discontinuity in mid-Oligocene time. Pliocene-Pleistocene fanglomerates are unconformable on folded rocks. There are discontinuous developments of Eocene-Oligocene neritic sediments unconformably above the older rocks (ophiolites, platform limestones, metamoprhic rocks), and to the north of the southern edge of the Jaz Murian Depression, the northern limit of the Makran, there is evidence of the survival here of a very shallow sea through Neogene time and the formation of small patches of reefal Oligocene-Miocene limestones, and Eocene to Pliocene shallow-water clastic sediments. A 150 km wide tract separates the coast from the trench, the total Cenozoic accretionary prism being 500 km wide. Extension from the Murray Ridge affects the extreme east of the region. The Saravan accretionary prism, it is suggested, faced a gulf, comparable with the Gulf of Oman, and this Saravan Gulf filled up and closed up by Early Oligocene time. Seismological evidence suggests that there is now active continental collision continuing along this suture.

Extrusive Members of Postcollisional A-Type Magmatism in Central Anatolia: Karahidir Volcanics, Idis Dagi-Avanos Area, Turkey

The Idis Dagi Igneous Complex is one of a number of late-stage plutonic bodies within the Central Anatolian Crystalline Complex. It intrudes Paleozoic-Mesozoic metamorphic basement rocks and Late Cretaceous granitoids. The complex comprises mainly quartz syenites and alkali-feldspar quartz syenites known as the Idis Dagi Syenitoids. Trachydacitic, trachyandesitic, and dacitic rocks (Karahidir Volcanics) have been recently found as dikes cutting the Idis Dagi Syenitoids or as huge blocks within an olistostromal unit of latest Cretaceous(?)-Early Paleocene age that immediately overlies the Idis Dagi Igneous Complex. Petrographic and geochemical data indicate that the Idis Dagi Syenitoids and the Karahidir Volcanics display similar humped patterns on chondrite- and MORB-normalized spider diagrams, with peaks at Rb, Th, and Ce, and also negative Nb anomalies. These features are similar to patterns considered typical of postcollisional, A-type igneous rocks. A postcollisional setting is also suggested by the distribution of data on tectonic discrimination diagrams involving Nb, Y, and Rb. As a whole, the geochemical data suggest that the Idis Dagi Syenitoids and Karahidir Volcanics are cogenetic. Thus, the Karahidir Volcanics represent the shallow intrusive and volcanic equivalents of the deeper-level Idis Dagi Syenitoids. The syenitoid rocks are considered the final phase of the magmatism in the Central Anatolian Crystalline Complex and are classified as post-orogenic alkaline rocks. Their chemical features suggest a largely mantle-derived magma contribution, together with a noticeable crustal component in their genesis. They were formed during postcollisional uplift that followed crustal thickening related to the southward emplacement of ophiolitic nappes during closure of the Izmir-Ankara-Erzincan Oceanic strand of Neotethys. The Karahidir Volcanics were exposed during regional extension that resulted in the formation of latest Cretaceous(?)-Early Paleocene extensional basins, and were emplaced as huge blocks into the continental clastic rocks by gravity sliding. This extension phase is characteristic of the development of all the other latest Cretaceous-Early Tertiary intracratonic basins in central Anatolia.

3 - SOUTHERN TUSCANY - B - COLLINE METALLIFERE

In the last decades the geology of Southern Tuscany (Giannini et al., 1971; Boccaletti et al., 1982, cum bibl.) has been greatly improved by lithostratigraphic, biostratigraphic and geophysic studies, and by deep geothermal drillings (with a depth down to 3000 m b.g.l.) (Bertini et al., 1991; 1994; Elter and Pandeli, 1996, cum bibl.). The geological setting of this area is composed, from top to bottom, of the following tectono-stratigraphic units (Figs. 1 and 2): a. Neo-autochthon (post-orogenic). It is formed by the sediments filling the extensional basins, generally oriented along to the Apenninic chain. They unconformably lie on the stack of Ligurian and Tuscan Units, and are represented by lacustrine-marine (late Tortonian-Messinian), marine (Pliocene) and lacustrine-fluvial (early Villafranchian-Quaternary) sediments. b. Ligurian, sub-Ligurian and epi-Ligurian Units. They are composed of five tectonic units: 1- Upper Ophiolitic Unit (Late Jurassic-Early Cretaceous: Vara Supergroup), largely represented by Palombini Shales with some ophiolitic outcrops. 2- Lower Ophiolitic Unit, (Jurassic-Early Cretaceous: Vara Supergroup), including thick ophiolitic successions. This unit is stratigraphically capped by: 3- The syn-orogenic Upper Paleocene- Middle Eocene epi-Ligurian Lanciaia Fm. (ophiolitic breccias and sandstones, grading upward to a mainly carbonate-siliciclastic flysch). 4- Monteverdi Marittimo Unit (Southern Tuscany Elminthoid Flysch Group): consisting of a calcareousmarly- arenaceous flysch of Late Cretaceous- Early Paleocene age. 5- Canetolo Unit (Paleocene- Middle/Late Eocene), made up of shales with limestone, calcarenite and graywacke intercalations. This unit belongs to the sub-Ligurian paleogeographic Domain (close to the Adria margin). c. Tuscan Nappe. It is composed, from top to bottom, of the following non-metamorphic formations: Macigno (Late Oligocene-Early Miocene), “Scisti Policromi” (Early Cretaceous- Oligocene), Tuscan Cherts (Malm), Posidonia Marlstones (Dogger), “Rosso Ammonitico” and Limano Cherty Limestones (Middle-Late Liassic), “Calcare Massiccio” (Late Triassic?-Early Liassic), Spezia Fm. (Rhaetian), Burano Anhydrites (Norian-Rhaetian). In this succession lateralvertical facies changes and sedimentary unconformities are present, mainly in Middle-Late Jurassic times. Furthermore, the Tuscan Nappe is often tectonically laminated or locally lacks (“Serie Toscana Ridotta” = Reduced Tuscan Series Auctt.) by low-angle extensional faulting with flat-ramp-flat geometry (Fig. 3). The Tuscan Nappe lies on the Tuscan Metamorphic succession (Monticiano-Roccastrada Unit) which is quoted below. d. Monticiano-Roccastrada Unit. The upper part of this unit is a complex pile of tectonic slices made up of epimetamorphic Lower to Upper Paleozoic formations, Triassic “Verrucano”, Tocchi Fm. and non-metamorphic Upper Triassic anhydrite-carbonate successions. The lower part is made up of ?Upper Cambrian-?Lower Ordovician siliciclastics and metabasites (Phyllitic-quartzitic Complex), which include relics of Hercynian schistosity. In the subsurface of Larderello geothermal area, the Phyllitic-quartzitic Complex overlies ?Lower Paleozoic/?pre-Paleozoic Micaschist Complex (see Stop 5). The Colline Metallifere area is characterised by high heat flow (>650 mWm-2 in the Larderello geothermal field), by lithosphere thinning (Moho at a depth of about 22 km in the Grosseto area), by the uplift of the metasomatised and partially melted mantle, and by anatectic crustal magmatism (Boccaletti et al., 1985; Mongelli et al., 1991).

Paleocene coccoliths and coccospheres in deposits of the Maastrichtian stage at the `type locality' and type area in SE Limburg, The Netherlands

Three so-called `Tertiary Newcomer Coccoliths'— Cruciplacolithus primus, Neobiscutum parvulum and Neobiscutum romeinii—were found in what are generally believed to be upper Maastrichtian deposits at the ENCI quarry, St. Pietersberg near Maastricht, the CURFS quarry near Houthem and from the Maastrichtian part of the K/T boundary section of the cave system at Geulhemmerberg near Valkenburg, southeastern Limburg, The Netherlands. The mentioned species appear already far below The Berg en Terblijt Horizon at the CURFS quarry and Geulhemmerberg, which is actually supposed to mark the K/T boundary, at the ENCI quarry they range throughout the Maastricht Formation above the Horizon of Lichtenberg. The specimens are well preserved and originate from undisturbed sediment layers, thus it seems that they were not transported into the Maastrichtian sediments by water circulation or burrowing effects. The state of preservation and the presence of intact coccospheres indicate that they are autochthonous. C. primus, N. romeinii and N. parvulum are extremely small in size (800 nm to 2.0 μm), implying that a scanning electron microscope (SEM) must be set at least to 3 K magnification in order to detect them. With a light microscope (LM) at 1 K they cannot be classified, which is probably the reason why previous investigators who studied the same sections based on LM did not mention these species from the upper Maastrichtian. They furthermore appear in very low numbers contributing to around 1% of an associated calcareous nannoflora which is equivalent to the assemblage of the CC26 Nephrolithus frequens Zone of Cepek and Hay (1969). The biostratigraphic setting of the ENCI quarry, CURFS quarry and Geulhemmerberg have been the subject of a long and controversial discussion whether the exposed sediments still belong to the upper Maastrichtian or represent the lower Tertiary. Reworking of macrofossils and microfossils or autochthony of index fossils had been discussed and used to support the different opinions about the chronostratigraphy of these sections. Up to now there has not been any contribution which might lead to convincing data. If C. primus, N. romeinii, and N. parvulum are indeed `Tertiary Newcomer Coccoliths', the sediments exposed above the Horizon of Lichtenberg at the ENCI quarry, and the sediments below The Berg en Terblijt Horizon studied at CURFS quarry and Geulhemmerberg do belong to the NP 1 Biantholithus sparsus Zone, which means they are of Early Paleocene age. However, if these coccoliths already originate in the late Maastrichtian, the definition of the K/T boundary by calcareous nannoflora must be revised.

Review: “The Hydrogeology of the Chalk of North-West Europe”

The chalk deposits of Late Cretaceous and Early Paleocene age in and around the present North Sea Basin form an important regional aquifer in the shallow subsurface on the basin perimeter, and a major hydrocarbon reservoir in the deeper parts of the basin. Currently, about 8.5 million cubic meters of water are pumped daily from the chalk. About 80 percent of the withdrawal is in southern England and northern France. This book provides an overview of the regional hydrogeology of the chalk, with primary emphasis on the fresh-water reservoir. The first six chapters of the book discuss topics applicable to the aquifer as a whole. Chapter 1, "The Making of an Aquifer," briefly describes the regional structure and stratigraphy and the diagenesis and modification of the chalk into a regionally extensive aquifer. Chapter 2, "The Formation and Diagenesis of the Chalk," poses the question, "Why so much chalk?" It explains how the combination of a rise in sea level, lack of erosion in nearby land areas, and higher temperatures and higher C02 in the atmosphere during Late Cretaceous time led to the extensive accumulation of chalk ooze. The resulting rock consists almost entirely of skeletal fragments of algae composed of lowmagnesium calcite. Chapter 3, "The Chalk as an Aquifer," describes the dual-porosity nature of the chalk, which generally consists of a highly porous matrix of low permeability and a fracture network that contains both tight tectonic fractures and highly permeable karstic fissures. Flow in the unsaturated and saturated zones is described in detail, and downgradient changes in the groundwater chemistry are discussed. The other three introductory chapters discuss simulation of flow and transport, engineering geology, and groundwater pollution in the chalk. The middle section of the book provides descriptions of the chalk aquifer in France, Belgium, the Netherlands, Denmark, Sweden, and the United Kingdom. These six chapters generally describe the aquifer extent, stratigraphy and structure, aquifer properties, groundwater levels and potentiometric surfaces, recharge and discharge characteristics, natural water chemistry and pollution, and current groundwater development in each country. The section on France provides a detailed discussion (15 pages) that relates groundwater levels and flow in the chalk of the Paris Basin to geologic structures, topography, and karstic networks. Ground pollution by nitrates and pesticides also receives a lot of attention. The chapter on Belgium consists largely of descriptions of the three major chalk aquifers: the Hesbaye aquifer, the Mons Basin, and the confined aquifers of northern Belgium, with emphasis on modeling approaches. The chapter describes a complex, 5-layer finite-element model of the Hesbaye aquifer, incorporating pumping from wells and galleries, faults, and various geologic unit boundaries. The stratigraphy and lithology of the chalk in the Netherlands are described for the two separate areas of occurrence in the northern and southern parts of the country. Detailed hydrogeologic information is presented only for the southern part of the Netherlands, where the aquifer is near surface and characterized by a matrix of high porosity and very low permeability; fractures and dissolution openings provide high secondary permeability. The chapter on Denmark contains brief summaries of the structure, stratigraphy, karst features, and aquifer properties; the principal focus of the chapter is on hydrochemistry, including natural chemical constituents and pollution problems. In Sweden, the occurrence ofthe chalk is limited to four areas in the southernmost part of the country. The structural setting, stratigraphy, aquifer properties, karstic features, water chemistry, and groundwater development are described for these areas. The chalk

New Early Paleocene Mollusca from the Wangaloa Formation of South Island, New Zealand

New Mollusca from the shallow marine, highly fossiliferous Wangaloa Formation of southeastern Otago, South Island, New Zealand, are described. This paper reports three new species and one new genus: Leionucula palaioanaxea n. sp. of the Nuculidae, Pyropsis zinsmeisteri n. sp. of the Tudiclidae, and Wangacteon grebneffi n. gen. and sp. of the Acteonidae. These taxa represent new records in New Zealand of apparently endemic taxa. The molluscan fauna of the Wangaloa Formation is important in the understanding of Paleogene biogeography of the Southern Hemisphere and changes in faunal composition of the Cretaceous–Tertiary Gondwana Realm. Genus- and species-level endemism in the “Wangaloan” fauna is marked and is probably a reflection of “greater New Zealand” 's geographic and genetic isolation during the Paleocene. Although deposits containing early Paleogene Mollusca are generally rare in the Southern Hemisphere, comparisons of known Gondwana molluscan taxa and those of similar age in the Northern Hemisphere indicate that the Mollusca of the Wangaloa Formation have Early Paleocene affinities. Microfossil evidence, in addition, supports an Early Paleocene age for the fauna. However, an uppermost Cretaceous age is indicated for the basal part of the Wangaloa Formation stratigraphically below the shell beds, but the K–T boundary has yet to be located.

Paleocene to Middle Eocene Stratigraphy of Alabama: ABSTRACT

Each of the eight Paleocene to middle Eocene formations that crop out across Alabama contains similar lithofacies. Each of the formations is characterized by east to west thickening, representing one or more transgressive cycles. An integrated biostratigraphic framework of calcareous nannofossils and planktonic foraminifers demonstrates that individual formations are generally the same age throughout Alabama, although the base of some cycles may be older in southwestern Alabama. The lower Eocene strata were deposited in a more open-marine environment in eastern Alabama than the rapidly prograding sequence in western Alabama. The early Paleocene Clayton Formation contains calcareous nannofossils characteristic of Martini's Zones NP1, NP2, and NP3, and planktonic foraminifers typical of Stainforth's Subbotina pseudobulloides and S. trinidadensis Interval zones. The lower and middle parts of the Porters Creek Formation are of late early Paleocene age (Zone NP3 and S. trinidadensis and Morozovella uncinata Interval zones); the upper Matthews Landing Marl Member of the Porters Creek is of early late Paleocene age (Zone NP4 and M. angulata Interval zone). The Coal Bluff Marl Member of the Naheola Formation is also of early late Paleocene age (Zone NP5). The lower Gravel Creek Sand Member of the Nanafalia Formation is assigned to Zone NP5 and is separated by a significant unconformity from the middle and upper m mbers of the Nanafalia; the middle Ustrea thirsae and the upper Grampian Hills Member are late Paleocene in age (Zone NP7 and NP8 and Planorotalites pseudomenardii Range Zone). The lowermost marl beds of the Tuscahoma Sand in western Alabama are assignable to Zone NP9 and the P. pseudomenardii Range Zone, and the remainder of the Tuscahoma is assigned to Zone NP9 and the Morozovella velascoensis Interval zone (late Paleocene). The Hatchetigbee and Bashi Formations are of earliest Eocene age (Zone NP10 and lower part of Morozovella subbotinae Interval zone). A major unconformity separates these formations from the overlying Tallahatta Formation, which is assignable to Zones NP12, NP13, and NP14, resulting in a late early Eocene age for the lowermost part of the Claiborne Group. End_of_Article - Last_Page 1430------------

K-Ar ages of basalt flows of the Meseta Buenos Aires in southern Chile and their relation to the southeast Pacific triple junction

The Meseta Buenos Aires faces the triple junction between the Nazca, Antarctic, and South American plates and consists of two olivine basaltic units separated by two sedimentary units. Seventeen whole-rock K-Ar age determinations gave a minimum age of 57 m.y. (late Paleocene) for the lower unit and ages ranging from 16 to 4.4 m.y. (early Miocene to Pliocene) for the upper unit. The Friasian Land-Mammal Stage sedimentary unit underlying the upper basaltic unit is assigned to the late Oligocene-early Miocene interval, and the marine sedimentary unit underlying the Friasian deposits and overlying the lower basaltic unit is assigned to the Eocene–early Oligocene interval. The lower basaltic unit rests unconformably on a marine fossiliferous sedimentary unit of probable Late Cretaceous to early Paleocene age. The basalts of the Meseta Buenos Aires are alkaline and are associated with andesite flows of tholeiitic character. The lower unit formed while the Farallon plate was being subducted under the South American plate, and any relation between this unit and the triple junction is excluded. The origin of the upper unit could be related to perturbations in the subcrustal mantle caused by the subduction of segments of the Chile Rise. Geochemical considerations, in addition to the fact that both basaltic units formed under different tectonic settings, are consistent with the hypothesis that the origin of the alkali basalts is independent of the environment in which they are found.