Michael A. Kaminski

The Cenozoic palaeoenvironment of the Arctic Ocean

The history of the Arctic Ocean during the Cenozoic era (0–65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm ‘greenhouse’ world, during the late Palaeocene and early Eocene epochs, to a colder ‘icehouse’ world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent ∼14 Myr, we find sedimentation rates of 1–2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (∼3.2 Myr ago) and East Antarctic ice (∼14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (∼45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at ∼49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (∼55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change.

The Cretaceous-Tertiary biotic transition

Mass extinctions are recognized through the study of fossil groups across event horizons, and from analyses of long-term trends in taxonomic richness and diversity. Both approaches have inherent flaws, and data that once seemed reliable can be readily superseded by the discovery of new fossils and/or the application of new analytical techniques. Herein the current state of the Cretaceous-Tertiary (K-T) biostratigraphical record is reviewed for most major fossil clades, including: calcareous nannoplankton, dinoflagellates, diatoms, radiolaria, foraminifera, ostracodes, scleractinian corals, bryozoans, brachio-pods, molluscs, echinoderms, fish, amphibians, reptiles and terrestrial plants (macrofossils and palynomorphs). These reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the K-T biotic crisis available. Results suggest that many faunal and floral groups (ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs) were in decline throughout the latest Maastrichtian while others (diatoms, radiolaria, benthic foraminifera, brachiopods, gastropods, fish, amphibians, lepidosaurs, terrestrial plants) passed through the K-T event horizon with only minor taxonomic richness and/or diversity changes. A few microfossil groups (calcareous nannoplankton, dinoflagellates, planktonic foraminifera) did experience a turnover of varying magnitudes in the latest Maastrichtian-earliest Danian. However, many of these turnovers, along with changes in ecological dominance patterns among benthic foraminifera, began in the latest Maastrichtian. Improved taxonomic estimates of the overall pattern and magnitude of the K-T extinction event must await the development of more reliable systematic and phylogenetic data for all Upper Cretaceous clades.

Last glacial–Holocene paleoceanography of the Black Sea and Marmara Sea: stable isotopic, foraminiferal and coccolith evidence

Multi-proxy data and radiocarbon dates from several key cores from the Black Sea and Marmara Sea document a complex paleoceanographic history for the last V30 000 yr. The Marmara Sea was isolated from both the Black Sea and the Aegean Sea during glacial periods when global sea-level lowering subaerially exposed the shallow sills at the Straits of Bosphorus and Dardanelles (i.e. lake stage), and reconnected through both straits during interglacial periods, when rise of global sea level breached the shallow sills (i.e. gateway stage). Micropaleontological data show that during the ‘lake stage’ the surface-water masses in both the Marmara Sea and Black Sea became notably brackish; however, during the ‘gateway stages’ there was a low-salinity surface layer and normal marine water mass beneath. Two sapropel layers are identified in the Marmara Sea cores: sapropels M2 and M1 were deposited between V29.5 and 23.5 ka, and V10.5 and 6.0 ka, respectively. Micropaleontological and stable isotopic data show that the surface-water salinities were reduced considerably during the deposition of both sapropel layers M2 and M1, and calculation using planktonic foraminiferal transfer functions shows that sea-surface temperatures were notably lower during these intervals. The presence of fauna and flora with Black Sea affinities and the absence of Mediterranean fauna and flora in sapropels M1 and M2 strongly suggest that communication existed with the Black Sea during these times. A benthic foraminiferal oxygen index shows that the onset of suboxic conditions in the Marmara Sea rapidly followed the establishment of fully marine conditions at V11^10.5 ka, and are attributed to Black Sea outflow into the Marmara Sea since 10.5 ka. These suboxic conditions have persisted to the present. The data discussed in this paper are completely at odds with the ‘Flood Hypothesis’ of Ryan et al. (1997), and Ryan and Pitman (1999). Crown Copyright > 2002 Elsevier Science B.V. All rights reserved.

Paleoecology, biostratigraphy, paleoceanography and taxonomy of agglutinated foraminifera

Agglutinated Foraminifera: An Introduction.- Why are Foraminiferida Foraminifers ?.- Composition and Microstructure of Agglutinated Foraminifer Wall.- Wall Structures of Palaeotextulariid Foraminifers and Discussion of Microgranular Test Walls.- Partitions and Fistulose Chamberlets in Textulariina.- Abyssal Agglutinates: Back to Basics.- On the Way to the Optimal Suprageneric Classification of Agglutinating Foraminifera.- Revision of the Trochamminacea and Remaneicacea of the Plymouth District S.W. England, Described by Heron-Allen and Earland (1930).- Agglutinated Foraminifera from the Palaeogene of the North Sea.- Gerochammina N.G. and Related Genera from the Upper Cretaceous Flysch-Type Benthic Foraminiferal Fauna, Eastern Carpathians - Romania.- Recent Deep-Sea Agglutinated Foraminifera: A Brief Review.- The Ecology, Distribution and Taxonomy of Crithionina Hispida Flint, 1899.- High Latitude Agglutinated Foraminifera: Prydz Bay (Antarctica) vs. Lancaster Sound (Canadian Arctic).- Biostratigraphy and Paleoecology of Deep-Water Agglutinated Foraminifera at ODP Site 643, Norwegian-Greenland Sea.- Danian Deep-Water (Bathyal) Agglutinated Foraminifera from Bavaria and Their Comparison with Approximately Coeval Agglutinated Assemblages from Senegal and Trinidad.- Paleoecology of Late Cretaceous to Paleocene Deep-Water Agglutinated Foraminifera from the North Atlantic and Western Tethys.- Deep Water Agglutinated Foraminiferal Assemblages from Upper Cretaceous Red Shales of the Magura Nappe / Polish Outer Carpathians.- The Oldest Assemblages of Agglutinated Foraminifers of the Polish Flysch Carpathians.- Faunal Trends and Assemblages of the Northern South China Sea Agglutinated Foraminifera.- Agglutinated Foraminifera in Organic-Rich Neritic Carbonates (Upper Cretaceous, Israel) and Their Use in Identifying Oxygen Levels in Oxygen-Poor Environments.- Agglutinated Foraminifera from the Albian and Cenomanian of Jordan.- Facies Controlled Distribution of Foraminifera in the Jurassic North Sea Basin.- Variations in Estuarine Foraminiferal Biofacies with Diminishing Oxygen Conditions in Drammensfjord, SE Norway..- Seasonality in the Benthic Foraminiferal Community and the Life History of Trochammina Hadai Uchio in Hamana Lake, Japan..- Recent Marsh Foraminifera from the East Coast of South America: Comparison to the Northern Hemisphere.- Estuarine and Marsh Foraminifera from the Lower Cretaceous of the Lusitanian Basin, West Portugal.- Recent Marsh-Type Agglutinated Foraminifera from Inland Salt Springs, Manitoba, Canada.- Biogeographic Distribution of Modern Thecamoebians in a Transect Along the Eastern North American Coast.- Thecamoebians from the Early Cretaceous Deposits of Ruby Creek, Alberta (Canada).- Fossil Thecamoebians: Present Status and Prospects for the Future.- Stratigraphically Important Agglutinated Foraminifera in the Badenian (Miocene M4) of Poland.- Foraminiferal Biostratigraphy and Seismic Sequences - Examples from the Cenozoic of the Beaufort-Mackenzie Basin, Arctic Canada.- Deep-Water Agglutinated Foraminifera from the Massignano Section (Ancona, Italy), a Proposed Stratotype for the Eocene-Oligocene Boundary.- Agglutinated Foraminifera, Biostratigraphy and Intraregional Correlation of Upper Cretaceous Deposits of Eastern Urals.- Cretaceous Agglutinated Foraminifera of the UK: A Review.- Agglutinated Foraminiferida from the Albian / Cenomanian Boundary in SE England.- The Application of Middle Jurassic-Early Cretaceous Agglutinated Foraminifera to the Offshore Correlation of Humber Group Sediments in the North Viking Graben.- Agglutinated Foraminiferal Stratigraphy of Middle Jurassic to Basal Cretaceous Shales, Central Spitsbergen..

Deltas south of the Bosphorus Strait record persistent Black Sea outflow to the Marmara Sea since ∼10 ka

At the southern exit of the Bosphorus Strait in the northeastern Marmara Sea, high-resolution seismic profiles reveal two lobate, progradational delta lobes in modern water depths of V40^65 m. The younger delta was active from V10 to 9 ka based on radiocarbon dates of equivalent prodelta deposits and the elevation of its topset-to-foreset transition. The topset-to-foreset transition climbs in the seaward direction because the delta prograded into a rising sea. Low abundances of marine fauna and flora in the 10^9-ka interval support a deltaic interpretation. There are no rivers in the area that could have fed the delta; instead, all evidence points to the strait itself as the source of sediment and water. When this outflow was strongest (V10.6^6.0 ka), sapropels accumulated in basinal areas of both the Aegean and Marmara seas. Benthic foraminiferal and dinoflagellate cyst data from contemporary deposits elsewhere in the Marmara Sea point to the continual presence through the Holocene of a surface layer of brackish water that we ascribe to this same outflow from the Black Sea through the Bosphorus Strait. By V9.1^8.5 ka, two-layer flow developed in the Bosphorus Strait as global sea level continued to rise, and the sediment supply to the younger delta was cut off because the outflowing Black Sea water ceased to be in contact with the floor of the strait. The older delta lobe lies below a prominent lowstand unconformity and is tentatively interpreted to have formed from V29.5 to 23.5 ka (oxygen-isotopic stage 3) when the Marmara Sea stood at V355 m and a second sapropel accumulated in deep basinal areas. Crown Copyright ? 2002 Elsevier Science B.V. All rights reserved.

Late Glacial to Holocene benthic foraminifera in the Marmara Sea: implications for Black Sea^Mediterranean Sea connections following the last deglaciation

Benthic foraminifera were studied from four gravity cores that penetrated Holocene marine sediments in the Marmara Sea. Morphogroup and assemblage analyses reveal that the Holocene sea-level rise did not result in a catastrophic flooding event as proposed by W.B.F. Ryan and others, whereby well-oxygenated, saline Mediterranean waters rapidly inundated a low-lying low salinity ‘Black Sea Lake’ at V7.15 ka (popularly known as the ‘Noah’s Flood Hypothesis’). Rather, the benthic foraminiferal data confirm the hypothesis that the Dardanelles sill was breached by the Mediterranean at V12 ka, allowing saline waters to penetrate the Marmara Sea. These saline waters reached the level of the Bosphorus sill at V9.5 ka, but were unable to penetrate into the Black Sea until after V9.1 ka because of the persistent strong outflow of brackish to fresh water from the Black Sea. The initial colonisation of the Marmara Sea by benthic foraminifera is essentially synchronous with the re-establishment of marine connections through the Dardanelles Strait at V12 ka. By V10 ka, Ammonia-dominated faunas developed on the strait-exit delta (v1) at the southern end of the Bosphorus, and at V9.1 ka the appearance of fully marine species documents the establishment of a more stratified water column over v1. Finally, the increase in abundance of planktonic foraminifera at the southern exit of the Bosphorus after V6.1 ka reflects a decreased volume of outflow water from the Black Sea. Quantitative analysis of benthic foraminiferal morphogroups reveals that the oxygen content of subhalocline water was low (below V1.5 ml/l) throughout the Holocene, and the occurrence of sapropel sediment in the deeper part of the basin suggests bottom waters may have been anoxic at times. After V4.5 ka, an increase in benthic foraminiferal oxic morphotypes suggests a reduction in Black Sea outflow and weakening of the halocline. The strong and persistent stratification of the water column in the Marmara Sea throughout the Holocene is entirely incompatible with the ‘Noah’s Flood Hypothesis’. : 2002 Elsevier Science B.V. All rights reserved.

Palaeocene-Eocene deep water agglutinated foraminifera from the Numidian Flysch (Rif, Northern Morocco); their significance for the palaeoceanography of the Gibraltar gateway

A lower bathyal to abyssal agglutinated foraminiferal fauna (over 78 taxa belonging to 31 genera) is documented from Palaeocene–Eocene deep-water sediments of the Numidian Flysch (Talaa Lakrah Unit) in Northern Morocco. The sample locality is adjacent to the Strait of Gibraltar, which comprised an oceanic ‘gateway’ between the Tethys Ocean and the North Atlantic during the Palaeogene. The chronostratigraphy of the section is based upon long-distance comparisons with the stratigraphic ranges of identified species in the North Atlantic region and the Polish Carpathians. Although no major evolutionary turnover among deep-water agglutinated foraminifera (DWAF) is observed across the Palaeocene/Eocene boundary, a change from Palaeocene Aschemocella- and Trochamminoides-dominated assemblages to an early Eocene Glomospira assemblage is recognized. This Glomospira biofacies occurs throughout the North Atlantic and western Tethys and may indicate lowered productivity and widespread oxygenated deep-water conditions during the early Eocene greenhouse conditions. A change to an overlying Reticulophragmium amplectens biofacies in green claystones reflects renewed higher productivity. Taxonomic affinities and the succession of benthic foraminiferal assemblages from the Gibraltar gateway display greater affinities to Tethyan assemblages than North Atlantic assemblages. This is interpreted as faunal evidence for a late Palaeocene to early Eocene equivalent of ‘Mediterranean outflow water’, flowing from the western Tethys into the Atlantic.

Monitoring the recolonization of the Mt Pinatubo 1991 ash layer by benthic foraminifera

Benthic foraminifera from the South China Sea were studied to assess mass mortality and to monitor the composition and recovery of the benthic communities following the 1991 Mt Pinatubo ashfall. Surface distribution data from monitoring stations in the eastern South China Sea that were occupied during four cruises between spring 1994 and summer 1998 display the following trends in recolonization patterns: (1) Suspension feeding epifaunal benthic foraminifera (i.e. Cibicidoides wuellerstorfi, Saccorhiza ramosa) and large xenophyophores (i.e. Syringammina (?)fragilissima) were absent in spring 1994 and only rare individuals were observed in June 1996, but in larger numbers in December 1996 and in summer 1998. Then, they were important recolonizers of the ash layer. (2) Diversity and population densities have changed significantly since 1994. Following an abundance maximum in winter 1996, the numbers of living individuals in summer 1998 decreased again and the deep sea benthic foraminiferal community started to return to a normal ecological structuring. However, infaunal foraminifera were still strongly dominated by several species of the genus Reophax. We interpret the changing abundance and diversity pattern during the recolonization process in two ways: (1) the markedly increasing activity of burrowing macrofauna observed since 1998 opened new ecological niches for infaunal benthic foraminifera but also intensified predator pressure; (2) competitive interactions within the recolonizing fauna began to play a major role. Opportunistic pioneer species, characterized by rapid reproduction rates and the capability to colonize disturbed environments, were outcompeted by non-opportunistic species

Evidence for ice-free summers in the late Miocene central Arctic Ocean

Although the permanently to seasonally ice-covered Arctic Ocean is a unique and sensitive component in the Earths climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger sediments from steep headwalls has led to exhumation of Miocene sediments close to the seafloor. Here we document the presence of IP25 as a proxy for spring sea-ice cover and alkenone-based summer sea-surface temperatures >4 °C that support a seasonal sea-ice cover with an ice-free summer season being predominant during the late Miocene in the central Arctic Ocean. A comparison of our proxy data with Miocene climate simulations seems to favour either relatively high late Miocene atmospheric CO2 concentrations and/or a weak sensitivity of the model to simulate the magnitude of high-latitude warming in a warmer than modern climate.

Ecological structuring and evolution of deep sea agglutinated foraminifera — a review

Abstract Recent agglutinated foraminiferal communities exhibit both simple and complex ecological structuring within habitats. Simple ecological structuring (i.e. a limitation of the entire fauna at or close to the sediment-water interface and absence of erect suspension feeding forms) is mainly observed under low oxygen conditions and high organic flux or after severe substrate disturbance. Oligotrophic deep sea conditions with low vertical particle flux and little substrate disturbance as in the central areas of the modern oceans lead to the development of complex ecological structuring with various highly adapted “specialists” (i.e. mobile infaunal forms, a variety of epifaunal suspension feeders, and epifaunal deposit feeders with special mechanisms to avoid energy loss and use food resources not exploitable by other organisms). The paleontologic record of species diversity and habitat preferences since the late Jurassic exhibits two trends: (1) a general trend from simple to complex ecological structuring within habitats leads to an overall increase in diversity; (2) fluctuations in this trend coinciding with major paleoceanographic events, i.e. changes in deep water oxygenation and paleoproductivity. From a comparison of Recent and fossil communities from various trophic situations we conclude, that the ecological structuring of agglutinated foraminifera within habitats may have been one of the most important driving forces (selection mechanisms) in the evolution of this special group of protists.