Biostratigraphy and Palaeoecology
Dr. Hartmut Jäger
Institut für Geowissenschaften
Im Neuenheimer Feld 234 / Room 113
0049 (0)6221-54 5335
Areas of Expertise:
Palaeozoic palynology - especially Upper Palaeozoic spores
Palynofacies analysis - interpretation of palaeoenvironments, distribution and preservation of organic matter, correlation of sedimentary facies to palynofacies
Microbial life in exotic environments
Neoproterozoic palynology - early evolution of life and Snowball EarthOrganofacies analysis and hydrocarbon generation
Organic Maturation - vitrinite reflectance, colour indices
Basin analysis - Palaeozoic basins of Central and Western Europe and N-Africa
Palynofazies (Sedimentologie organischen Materials) / Palynofacies Analysis
Kohlenwasserstoff-Lagerstätten / Petroleum Geology
Commission Internationale de Microflore du Paléozoique (CIMP) - Secretary of Spore/Pollen Subcommission
American Association of Stratigraphic Palynologists (AASP)
German Subcommission of Carboniferous Stratigraphy
Deutsche Geologische Gesellschaft / German Geological Society (DGG)
1) Neoproterozoic palynology
1.1) Early Evolution of Life in the Neoproterozoic
Life on earth is known since the Archean, at least 3,5 billion years. Since the late 1960’s numerous studies indicated, that life developed from these oldest fossils and evolutionary lineages went on continuously throughout the Proterozoic. Diversity studies show a slow increase during the Palaeo- and Mesoproterozoic followed by a jump in diversity and evolution of microscopic but also macroscopic life in the Neoproterozoic. Detailed studies of the upper Neoproterozoic showed a strong decrease in diversity in the basal Ediacaran, linked to a widespread glaciation, but life went on continuously. This scenario was generally accepted until the theory of ‚Snowball Earth’ arose, questioning the continuous evolutionary lineages from the Proterozoic into the Cambrian. This theory proposed global glaciations in the Neoproterozoic leading to the break down of the life cycle in the oceans, followed by mass extinctions. Detailed studies of this interval (especially the ‘Marinoan’ glacial event) in recent years recorded this gap of life in the critical interval in the Neoproterozoic. Studies of mainly carbonate successions from pre- to post-glacial formations of the Ghaub glacial event ('Marinoan') in NE-Namibia (Otavi Mountain Land) recorded the first continuous record of life across the Neoproterozoic ‘Marinoan’ glacial event worldwide. The complex microbial association of benthic prokaryotes (cyanobacteria) and eukaryotes (green algae) as well as planktic eukaryotes (acritarchs, prasinophytes) essentially requires open oceans with an active hydrologic cycle, ice-free shelfs and access to the sea floor. This proves the continuous evolution of marine life during the proposed ‘Snowball Earth’ period. No mass extinction or severe crisis of marine life is observed, clearly contradicting the hypothesis of global glaciations with globally frozen oceans. To explain widely distributed low latitude glaciations coexisting with continuous life in the oceans a different scenario is needed – the Neoproterozoic Ice Patch Earth. The study of organic microbiota is currently expanded to a much longer succession from the pre-glacial Ghauss Fm to the top of the postglacial Maieberg Fm. The study of the postglacial Maieberg Fm may also enable the analysis of the recovery of life after the most widespread glaciation in earth history and the interaction of microbial and macrofossil evolution in the late Neoproterozoic. For a better understanding of the early evolution of life during Neoproterozoic glaciations further investigations are planned in 'Marinoan' sections in Congo, Oman and China.
1.2) Palynofacies Analysis in the Neoproterozoic and the Neoproterozoic Climatic Paradox
Neoproterozoic diamictites at low palaeolatitudes overlain by "Cap Carbonates" led to the hypothesis of at least 2 global glaciations, known as "Snowball Earth". The Cap Carbonates associated with negative -δ13C excursions are a key point of this theory, interpreted as a result of the collapse in organic productivity in the ocean, due to the isolation of global oceans from the atmosphere by the global ice cover. Therefore Cap Carbonates were interpreted as anorganic precipitates produced by the switch from "Snowball Earth" into a super green house – the Neoproterozoic Climatic Paradox. Although this hypothesis is widely accepted today, there is independent sedimentary evidence that areas of open ocean coexisted with low latitude sea-ice (Embelton & Williams 1986) and for advance and retreat of wet based glaciers (Allen et al. 2004). Palynological studies of Cap Carbonates from the late Neoproterozoic Maieberg Fm in NE-Namibia prove a continuous record of life within the Cap Carbonates, dominated by cyanobacteria with few prasinophytes and acritarchs. The decrease of organic matter (TOC) in the Cap Carbonates is not related to less organic productivity in the oceans, but to facies changes to extremely shallow marginal marine conditions of a proximal carbonate platform. Palynology proves, that cap carbonates are mainly biogenic or at least biomediated deposits (and not solely anorganic precipitates), requiring open oceans and ice-free sea floors during this aftermath of the main glacial interval. Palynofacies analysis gives clear evidence for sea-level fluctuations within the Cap Carbonates. Variations in relative sea-level are recorded by changing proportions of prasinophytes and acritarchs within the generally very shallow, marginal marine environment, dominated by microbial mats (cyanobacteria). This indicates continued climatic variability during Cap Carbonate deposition, contradicting its interpretation as a deposit of a single large marine transgression at the end of the global glaciation, assumed by the ‘Snowball Earth’ theory. The continuous record of fluctuations in relative sea-level coeval with dropstones contradicts the rapid change from a ‘Snowball Earth’ to a super greenhouse during the Cap Carbonate deposition, but supports a model of long term waxing and waning of glaciers within a relatively slow escape from a widely glaciated Neoproterozoic world.
1.3) Neoproterozoic Glaciations and Infracambrian HC Systems
Neoproterozoic petroleum systems are still little known. Generally post-glacial highstand deposits are seen as major source rocks for these ‟Infracambrian‟ petroleum systems. Analogue to the deposition of Silurian black-shales following the late Ordovician glaciation as a major source rock interval in Northern Africa, organic-rich deposits during the massive rise of sea level following “Snowball Earth” are seen as major source rock units along Northern Gondwana from Northern Africa to India and Australia. In northern Namibia, on the shelf of the southern margin of the Congo craton, different subbbasins developed before, during and after the „Marinoan‟ glaciation, due to repeated tensional activity. The postglacial sea-level rise, most probably accompanied by restricted circulation, widely flooded the newly formed relief (shelf and subbasins) and led to the deposition of organic-rich shaly limestones. But also during preglacial times basin developement led to the deposition of organic-rich carbonates, assuming high HC source rock potential. The study covers continuous successions from the preglacial Auros Fm. through the synglacial Ghaub Fm. to the postglacial Maieberg Fm. in different shelf to basin positions. Apart from the Ghaub diamictites, the whole sucession is composed of mainly dark, organic-rich, micritic carbonate shelf deposits. Source rock analysis is focused on the quantity and the quality of organic matter, based on the compostion of the kerogen (organofacies analysis) and organic maturation. Comparing hydrocarbon source rock characteristics and prospectivity of pre- and postglacial Neoproterozoic deposits in Namibia shows, that under certain conditions HC source rock potential is even higher in preglacial than in postglacial successions. Therefore the well exposed carbonate sucessions of ‟Marinoan‟ pre- to postglacial deposits in northern Namibia represent a good outcrop analogue for both, preglacial and postglacial source rocks of glaciogenic petroleum systems in the Neoproterozoic worldwide.
2) Palynology of carbonate shelfs
2.1) Palynology of platty limestones in the Cretaceous of Mexico
Palynofacies analysis shows very interesting details of the palaeoenvironmental conditions during Plattenkalk formation. Palynofacies will not contribute data for biostratigraphic correlations, because planctonic marine palynomorphs (e.g. dinocysts) are absent and terrestrial palynomorphs (mainly bisaccate Pollen) are very rare. But it will provide crucial information on the palaeoenvironmental and palaeoecological conditions in the Plattenkalk and therefore strongly improve the understanding of the formation of these deposits. Quantitative palynofacies analysis may show certain events that can be traced as marker horizons within an event stratigraphic scheme. To improve palaeoenvironmental interpretations correlated to basic geochemical data, palynological samples will be analized for TOC/CNS and stable isotopes from the organic matter.
2.2) Palynological analysis of Limestone-Marl-Alternations
It is an ongoing debate about the origin of limestone-marl alternations. On one side it is interpreted as product of primary differences in the sediment input, linked to high frequency cyclicity in the depositional system. On the other side it is seen as secondary effect due to diagenetic differentiation of primary homogenous deposits, leading to a totally different model for the depositional system. Often it is difficult to distinguish between primary and diagenetic features in micritic rhythmites, but this is essential
for any further interpretation of the successions. In opposite to mineral components (often effected by diagenesis) sedimentary organic matter (SOM) seems to have good potential to preserve information on the origin of primary sediments and therefore to distinguish primary from secondary micritic successions.
Palynological analysis is based on total composition of SOM, the distribution of certain groups of marine and terrigeneous organic matter and palynofacies proxies (e.g. terrestrial:marine Index) in limestones and marlstones of directly connected limestone-marlstone couplets. Currently sections are studied from the Cretaceous of Brazil (Sergipe Basin) and southern Portugal (Algarve Basin) just as the Silurian of Gotland.
3) Palynological analysis of Palaeoclimatic and palaeoenvironmental changes
3.1) The palynological analysis of intervals of potential ocean acidification
Ocean acidification is the process of the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere. Extreme rises of CO2 levels can even lead to carbonate dissolution in shallow marine environments, and favour marl- and mudstone deposition as residual sediments. Certain intervals in earth history characterized by the decrease of carbonate production and widespread increase of marl-and mudstone deposits in shallow marine shelf systems are seen as potential intervals of ocean acidification. For a better understanding if and how ocean acidifcation took place in these intervals, changes in the composition and preservation of sedimentary organic matter are done. Currently studies are focused on the Triassic-Jurassic boundary in the Alps and mid-Cambrian carbonate shelf deposits in Sardinia.
4) Lower Carboniferous Palynology
4.1) Lower Carboniferous Palynology in Germany and central Europe
In Germany and Central Europe palynological studies of the Lower Carboniferous are rare. It started with mostly systematical investigations of pollen and spores from Upper Carboniferous coal seams (Ruhr Area, Saar-Nahe Basin), leading to the classical turma spore classification scheme for Palaeozoic spores. In the 1960s and 1970s the focus switched to palynostratigraphic studies of the Devonian / Carboniferous boundary mainly in the Rhenish Slate Mts. Because most of these studies were focussed on short stratigraphic intervals, no comprehensive miospore zonation has been established for the Lower Carboniferous in Germany and Central Europe. Therefore a series of detailed palynological studies with a wide stratigraphic range was started in Germany to establish a spore zonal scheme for the entire Lower Carboniferous, filling the 'gap' between the well established Lower Carboniferous spore zonal schemes of Western- and Eastern Europe. Studies were concentrated on boreholes in northern Germany (off- and onshore NW-Germany, Rügen Island) and sections in the Rhenohercynian Zone (Rhenish Slate Mts., Harz Mts., Hörre-Gommern Zone). One study was carried out in the Visean sections in SE-Germany (Saxony). German miospore assemblages are closely comparable to western Europe and Poland and can be assigned to the Vallatisporites-Grandispora Microflora. Correlations can be made at several stratigraphic levels between these spore zonal schemes, but certain differences are observed also. Spore assemblages from off- and onshore NW-Germany are very closely comparable to Western Europe, whereas assemblages from Rügen Island are more closely comparable to Poland.
4.2) Distribution and Preservation of Palynomorphs across the Lower Carboniferous Shelf of Central and Western Europe
Late Visean strata are studied in wells from the southern North Sea, (Scotland to NW-Germany) Rügen Island (NE-Germany, southern Baltic Sea) and field sections in the northern Rhenish Slate Mts. (Velbert syncline), representing different depositional settings from proximal near-shore clastic facies (Firth of Forth, NW-Germany) via proximal to distal carbonate platform facies (Rügen Island) to platform slope facies (Velbert syncline). Variations of the miospore assemblages from age-equivalent parts of these sections were analyzed with respect to palynofacies, spore abundance, morphological composition, diversity and palaeobotanical / palaeoecological affinities. While assemblages from similar down-depositional dip facies settings remain similar (even over long distances of >750 km), all of the above attributes show significant variations from proximal to distal depositional settings, even on relatively short distances. These down-depositional dip changes appear to be continuous, but major changes are observed from deltaic and non-deltaic near-shore facies, between near-shore coastal clastic and carbonate platform facies; and between carbonate platform and slope facies. Miospore abundances, assemblage diversities and the number of coincident genera between the sections are reduced towards distal depositional settings. This decrease mostly effects rounded triangular and triangular miospores, while the proportion of rounded miospores increases significantly, leading to clear changes in the palaeobotanical / palaeoecological interpretation of the spore assemblages also. These changes appear to be largely controlled by taphonomic processes such as distribution and sorting during transportation and deposition, so that a facies-related pattern is apparent. Variations in late Viséan miospore assemblages across the studied area appear to be most closely related to the different facies realms suggesting that previously identified differences in miospore assemblages from Germany and the UK reflect differences in depositional facies rather than regional variations in parent vegetation or climate. Facies dependence of spore assemblages is an important factor for stratigraphical use of spores and for establishing vegetational and climatic trends.
4.3) Spore Assemblage Correlations across the Rhenohercynian Basin – Differences in Palaeobotanical Evolution of Laurussia and Peri-Gondwana in the Lower Carboniferous
Palynological studies are done in Lower Carboniferous (upper Viséan) strata near Chemnitz (Frankenberg Fm, Saxony, SE-Germany) in the very southeast of the Saxothuringian Zone at the northern margin of the Bohemian Massif. The sand-rich deposits of the Frankenberg Fm are typical delta- to floodplain sediments, including some siltstone layers and very rare thin-bedded sandy shales. These dark pelitic interlayers have recorded moderately to well preserved microflora, used for palynostratigraphy, spore assemblage analysis and palaeobotanical/palaeoecological interpretation. Most palynological studies in the Lower Carboniferous in Germany are from the northern part of Germany (NW-Germany, Rügen Island, Rhenohercynian Zone), located at or derived from the Laurussian shelf north of the Rhenohercynian basin. In opposite spore assemblages from Saxony are related to the shelf south of the Rhenohrcynian basin along the Bohemian Massif, which is part of Peri-Gondwana, an assembly of terranes along the northern margin of Gondwana. Samples from Saxony are compared to age equivalent samples from similar depositional settings from the North Sea area (Germany, UK). Palynofacies shows high similarities between both areas, but diversity is less in Saxony. Qualitative analysis of microflora shows some similarities between Saxony and the North Sea again, but about 30% of genera typical in North Sea samples are absent in Saxony. Major differences are observed in the quantitaive analysis of the microflora, leading to major differences in the palaeobotanical interpretation of the spore assemblages. Samples from Saxony are dominated by fern related spores, linked to non-forest mires. Lycopsid related spores are very rare to absent. In opposite spore assemblages from the North Sea samples are clearly dominated by lycopsid related spores, linked to forest mires. These differences are a result of primary differences in regional vegetation, because palaeoenvironmental settings of sample localities are closely comparable. Based on spore assemblage analysis palaeobotanical and palaeoecological correlations will be done along the northern margin of the Bohemian Massif towards the Carpathian foredeep just as along the Laurussian shelf from Northern Germany to Western Europe (UK, Ireland). The information on regional spore assemblage variations gives new insights on the distribution and evolution of terrestrial vegetation and different palaeoecological environments throughout Central Europe in the Upper Palaeozoic.
4.4) Rapid Environmental Changes on a Carbonate platform - High-Resolution Analysis of a Transgressive System Tract based on Palynofacies and Geochemistry
The Aran islands (west coast, Ireland) are made of Upper Visean limestones of typical carbonate platform facies. Several hundred meters of platform limestones represent a very stable palaeoenvironment of several million years duration, from the Asbian to the Brigantian. Within this thick limestone succession, a thin shaly interval was observed, providing evidence of significant palaeoenvironmental changes on the platform. The limited thickness and sharp lithological boundaries of the shaly interlayer suggest a very short-lived and rapid palaeoenvironmental change on the carbonate platform. Two different lithostratigraphic units can be distinguished within this interval. The lower part consists of medium grey mudstones with abundant pyrite nodules, showing strong lateral variation in thickness and even pinching out in places. The upper part consists of very dark grey shales, maintaining its thickness along the whole length of the accesible section. The lithological differences suggest a clear change of palaeoenvironmental conditions even within this short event. To obtain more information on these significant environmental changes, detailed palynological and geochemical studies were undertaken, including palynofacies analysis, clay mineralogy analysis, TOC and CNS and C-isotopes. First results suggest a change from restricted marine conditions almost without terrestrial input at the bottom of the unit, to shallow marine conditions with high terrestrial input at the top. The lower part of the shaly interval represents deposition within locally restricted minor depressions on the platform, isolated from both terrestrial input and from open marine environments. The upper part represents widespread deposition on the platform with substantial terrestrial input. This scenario can be explained by a drop of sea-level, leading to isolated ponds of sea-water on the platform cut off from any terrestrial input during the lowstand system tract (lst). During the following rise of sea-level, the platform was again widely flooded and large amounts of terrestrial organic matter were deposited on the platform. This transgressive system tract (tst) can be divided in 4 different phases showing the different levels of sea-level rise and connection to the hinterland. The very dark grey shales of the upper part of the interval seem to represent the maximum flooding surface (mfs), followed by a huge succession of carbonate platform deposits representing the highstand system tract (hst).
4.5) Upper Palaeozoic (Mississippian) Basin Evolution of Rügen Island, NE-German Basin
Until now the Lower Carboniferous of Rügen is interpreted as a typical carbonate platform, developed continuously from the Upper Devonian to the Lower Carboniferous at the margin of the Variscan foreland basin. The break up of this platform in the uppermost Visean led to the structural setting seen in seismic sections today. New studies of several boreholes from Rügen led to a strongly different model of the Lower Carboniferous depositional history, in the final phase of the Variscan orogeny. Palynostratigraphy shows significant stratigraphical gaps at the base and the top of the Lower Carboniferous. At the base the lower to middle Tournaisian is missing, linked to the major global regression at the Devonian/Carboniferous boundary, and at the top the middle to upper Visean is not preserved. The succession starts with typical platform carbonate deposits in the upper Tournaisian, followed by mainly resedimented carbonate deposits (carbonate debris flows, calciturbidites) throughout the Visean. Based on palynostratigraphic correlation and sedimentological analysis strongly diverging thickness per spore zone, sedimentation rates and processes just as differences in the overall stratigraphic range are observed in the different borehole sections. Major differences in subsidence are observed for each single block of Rügen, with rapid subsidence especially in the NE-part in the lower Visean followed by decreasing subsidence in the middle to upper Visean. The gradient of the subsidence increases from SW to NE, showing a northward dip of this intra-platform basin. Basin inversion led to uplift and erosion in the Upper Visean (to Lower Westphalian?) with a maximum in the NE-part, producing the large stratigraphical gap seen in these sections. This gives evidence for the collapse and break up of the platform around the Tournaisian/Visean boundary, leading to the development of an intra-platform basin in Rügen, similar to other intra-platform basins at this time in central and western Europe. For the quantification of this complex subsidence and uplift history a high resolution study of organic maturation (vitrinite reflectance) is done in selected boreholes. Erosional gaps will be quantified and the thermal history of the different blocks of this platform will be revealed. The stratigraphically and thermally controlled model of the evolution of the Lower Carboniferous carbonate platform from Rügen will be coupled with data from the variscan orogen, to analyse the interaction between the increasing crustal load due to the northward prograding orogenic front and increasing uplift within the foreland basin, especially along the margin, producing break up structures like the intra-platform basin of Rügen.
5) Organofacies analysis as part of the integrated analysis of hydrocarbon systems.
Since 2012: Principal Geologist Hydrocarbon Exploration at GeoResources Steinbeis-Transfer Centre, Heidelberg
Since 2011: External lecturer for palynology at the Ruprecht-Karls University of Heidelberg, Institute of Earth Sciences
2007 - 2010: Research Associate at the Ruprecht-Karls University of Heidelberg
2007 - 2011: Senior Geologist at GeoResources Steinbeis-TransferCentre, Heidelberg
2005 – 2006 Lecturer for Geology at the University of Karlsruhe.
2002 – 2004 Research Associate at the Ruprecht-Karls University Heidelberg.
1999 – 2000 Postdoctoral Researcher at Trinity College Dublin
1999 PhD at the Technical University of Darmstadt.
1996 DAAD Doctoral fellowship at Trinity College Dublin
1995 Diploma in Geology and Palaeontology at the Phillipps University Marburg
Internationale, peer reviewed Publikationen
Bechstädt, T., Jäger, H., Spence, G. and Werner, G., 2009, Late Cryogenian (Neoproterozoic) glacial and post-glacial succession at the southern margin of the Congo Craton, northern Namibia: facies, palaeogeography and hydrocarbon perspective, Geological Society, London, Special Publications, v.326, p. 255-287.
Jäger, H. & McLean, D. (2008): Palynofacies and spore assemblage variations of upper Viséan (Mississippian) strata across the southern North Sea. - Review of Palaeobotany and Palynology, 148: 136-153, Amsterdam.
Jäger, H. & Wierich, F. 2006: Chapter 6.2 Palynostratigraphie. - In: Deutsche Stratigraphische Kommission (Ed.): Stratigraphie von Deutschland. VI - Unterkarbon (Mississippium). – Schriftenreihe DGG., 41: 294-318
Jäger, H. (2004): Facies dependence of spore assemblages and new data on sedimentary influence of spore taphonomy. - Review of Palaeobotany and Palynology, 130: 121-140, Amsterdam.
Jäger, H. (2002): Palynology of the Lower Carboniferous (Mississippian) Kammquartzite Formation in the Rhenohercynian Zone, Germany. – Senckenbergiana Lethaea, 82 (2): 609-637, Frankfurt.
Jäger, H. & Gursky, H.-J. (2000): Alter, Genese und Paläogeographie der Kammquarzit-Formation (Visé) im Rhenoherzynikum – neue Daten und neue Deutungen. - Z. dt. geol. Ges., 151, 4: 415-441.
Jäger, H., Lewandowski, E. & Lampart, V. (2009): Palynology of the upper Silurian to middle Devonian in the Reggane Basin, Southern Algeria. - Abstracts. II. Joint meeting of CIMP Spores/Pollen and Acritarch Subcommissions, Faro, 47-51.
Jäger, H. & Lampart, V. (2009): Palynology of the upper Silurian to Middle Devonian of wells from the Reggane Basin, southern Algeria. DGMK/ÖGEW-Frühjahrstagung 2009, Celle, DGMK-Tagungsbericht 2009-1 (ISBN 978-3-936418-90-3)
Jäger, H. (2010): Mikrofloren aus dem Obervisé der Nordsee und Sachsens – Hinweise auf paläobotanische Unterschiede zwischen Laurussia und Peri-Gondwana. - Kurzfassungen, 80. Jahrestagung der Paläontologischen Gesellschaft, Zitteliana B 29, München.
Jäger, H., Spence, G. H. and Bechstädt, T. (2010): Palynology of glacial intervals in the Neoproterozoic of Namibia – new facts on ‘Snowball Earth’. - Abstracts Vol., CIMP General Meeting, Warsaw.
Jäger, H. & Bechstädt, T. (2009): Hydrocarbon source rock potential of Neoproterozoic glacial deposits in Namibia - preglacial versus postglacial source rocks. Glaciogenic reservoirs and petroleum systems, Meeting Geol. Soc. London, Petroleum Group, London
Jäger, H., Spence, G.H., Bechstädt, T., (2009): Sea level variations in Cap Carbonates from Namibia - consequences for Neoproterozoic climatic changes. Sediment 2009 Krakow, Abstracts Vol.
Jäger, H., Clayton, G. & Goodhue, R., 2008. Rapid environmental changes within a carbonate platform (Aran Islands, Ireland) – new insights from palynology and geochemistry
Jäger, H., Spence, G.H., Bechstädt, T., 2008. Organofacies of Neoproterozoic Cap Carbonates from Namibia – new data on Neoproterozoic extreme climates. Abstracts, Int. Palyn.Congr., Bonn.
Jäger, H., Andrade, E. de Jesus, 2008. Palynofacies of Limestone-Marl Alternations (Upper Cretacous, NE-Brazil). Abstracts, Int. Palyn.Congr., Bonn.
Jäger, H., Spence, G., Bechstädt, T., 2008. Organofacies evidence for Neoproterozoic cold-water Ice-Patch Earth. Abstracts, IAS SEPM-CES Meeting, Sediment 2008, Bochum.
Bechstädt, T., Jäger, H., Rittersbacher, A., Spence, G., 2008. Facies, Geochemistry and Palynology of a Neoproterozoic (Cryogenian) Postglacial Cap Dolomite at the Southern Rifted Margin of the Congo Craton (Northern Namibia). Abstracts, IAS SEPM-CES Meeting, Sediment 2008, Bochum.
Spence, G., Jäger, H., Bechstädt, T., 2008. Neoproterozoic Ice Patch Earth: The paradox of low latitude sea level glaciation coeval with regions of open ocean. - EUG General Assembly, Vienna.
Spence, G., Jäger, H., Bechstädt, T., 2006. A sedimentary, isotopic (d13C, d18O) and geochemical (TOC, N, S) investigation of a Neoproterozoic negative carbon isotope stage associated with a cap carbonate in the Otavi Mountain Land of Namibia: Significance for the Snowball Earth Model. – Abstract volume, Annual Meeting British Sedimentological Research Group, Aberdeen.
Jäger, H. 2006. Upper Visean palynology of the northern margin of the Bohemian Massif (Saxony, SE-Germany) and correlations across the Rhenohercynian Basin. – Book of Abstracts, CIMP General Meeting, Prag.
Jäger, H. & Andrade, E. 2005. Paleoenvironmental changes in the lower Turonian in the Sergipe Basin, NE-Brazil – the palynofacies analysis approach. – Abstracts, 19. Lateinamerika Kolloquium, GFZ Potsdam.