Henrich, Rüdiger
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Henrich, Rüdiger
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Henrich, Rüdiger
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Item-typ:Veröffentlichung, Southwest Atlantic intermediate and deep water circulation : 20,000 years of water mass re-organization and current strength variability(2017-12-12); ; ; As one of the major players of the Atlantic meridional overturning circulation, the deep southern component water (SCW), comprising Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW), ventilates the deep waters and influences global climate. However, detailed information about deep SCW strength are lacking, due to its corrosivity resulting in a lack of appropriate paleoceanographic archives. In order to improve the accuracy of ocean circulation variability, detailed deep SCW reconstructions require additional efforts from many branches of climate research. In the frame of this thesis, seven radiocarbon-dated Sediment cores from the Argentine continental margin (i.e. from contourite deposits, the Mar del Plata Canyon and the deep slope) were investigated. The core sites provide the opportunity to investigate the intermediate and deep water mass circulation, e.g. deep SCW flow strength variations, of the deep Southwest Atlantic during the last 20 ka. Furthermore, part of these sediment cores were used to analyze the influence of intermediate and deep ocean currents on sedimentary processes within a blind canyon system.Dissertation503 261 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Shifts in North Atlantic surface water regimes during the last interglacial-glacial cycle (late Quaternary) investigated by coccolithophore-based ecological and chemical proxies(2009-09-09); ; ; Coccolith-based palaeoenvironmental proxies were tested and applied for the reconstruction of environmental conditions and likely influences in the North Atlantic during the last c. 150 000 years (MIS 6-1), combining palaeoenvironmental tools such as coccolith assemblages, coccoliths carbonate contribution, fine fraction (<20 Ã µm) oxygen isotopes and morphometric analyses on Emiliania huxleyi on the sediment material of two sediment cores (ODP Site 980 and GeoB 11035-1). Coccolith assemblage studies and morphometric variations were successfully used to reconstruct climatic changes in the marine environment, especially glacial-interglacial and short-term stadial-interstadial variations. Though, partly uncertain results appeared in the application of the geochemical signal of the calcareous coccolith plates for palaeoenvironmental reconstructions, which are due to vital effects, polyspecific samples and the influence of non-coccolith carbonate.Dissertation511 141 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Stratigraphic evolution of the North Levant Platform (Syria) during Aptian to Early Turonian(2012-11-02); ; ; The Levant margin includes the easternmost part of the Eastern Mediterranean in a region where the oceanic (Tethyan) plates and the Arabian, African and Eurasian crustal plates interact. The tectonic events in relation with these plate deformations resulted in the division of the Levant into several provinces; the Southern, the Middle and the Northern. The studied area forms the Northern part of the Levant Platform. The combination of relative sea changes, tectonics, volcanism and local, regional and global environmental perturbations in the North Levant left imprints on the Aptian - Early Turonian carbonate platform configuration and depositional settings. The latter are reconstructed within a nimproved stratigraphic framework, based on field observations, high resolution biostratigraphy, geochemical analysis, detailed microfacies distribution and sequence stratigraphy. The Aptian Early Turonian succession of the North Levant in the South Palmyrides and Coastal Range of Syria represents two different depositional environments of the intra platform rifting basin (Palmyrides) and passive marginal basin (Coastal Range). Deposition was controlled by terrigenous input and/or nutrition resources, syn-depositional volcanic activity, climatic and sea level change which gives the Aptian and the Albian Early Turonian its characteristic features. A high resolution stratigraphic calibration of the Aptian - Early Turonian strata of the Coastal Range and South Palmyrides are based on the integrated identification of benthonic and planktonic foraminifera, in comparison with carbon isotope signals and (subsurface) logs. The abundant larger benthonic foraminifera in all outcrops of both areas allow to subdivide the Aptian - Early Turonian succession into 7 biozones in the Coastal Range and five in the South Palmyrides. Locally abundant planktonic foraminifera allow the subdivision of the latest Aptian - Cenomanian succession into seven biozones in the South Palmyrides, comparing to seven biozones range from the latest Albian to Early Turonian. Carbon isotope fluctuations record significant perturbations that are well comparable with several global changes of the carbon cycle: OAE1c, OAE1d, LCE I-III, MCE, and OAE2. The carbon isotope record is calibrated by high resolution biostratigraphic data, especially during rising sea levels. The comparison of the sequence stratigraphic interpretation with the major depositional systems shows that the depositional systems correspond very well with deepening-up, maximum flooding surfaces (mfs) and shallowing-up cycles that were applied to support the sequence stratigraphic model. Based on high resolution microfacies and gamma ray logs of five wells, the Aptian-Early Turonian succession was subdivided into eleven 3rd order (Syrian) depositional sequences, bounded by major unconformities. Three Aptian sequences of the Coastal Range and the South Palmyrides with mfs K80, K81S, K82S correlate partly with Arabian mfs (v. Buchem et al., 2012); four Albian sequences of the Coastal Range and two of the South Palmyrides with mfs K83S, K100, K110, K120 and five Cenomanian sequences (mfs K121S, K130, K131 S, K140) are defined.Dissertation331 155 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Styles of continental margin sedimentation: comparing glaciated and non-glaciated slope systems using case studies on the southeast Canadian and northern Argentine and Uruguay continental slope(2011-10-17); ; ; Continental slope sedimentation is in generally driven by climate and the oceanographic setting along a margin. This work compares slope architecture of the glaciated Scotian Slope to the nonglaciated northern Argentine slope. On the Scotian Slope, a new seismic stratigraphy was used to identify variations in patterns of slope sedimentation. The Early Quaternary is characterized by few mass transport deposits (MTDs) and deposition occurs at the lower slope, whereas towards the younger glaciated sequence, much larger MTDs characterize slope sedimentation. On the Argentine Slope, sedimentation patterns are driven by along- and downslope processes. At times of large Pleistocene storm events at the shelf break, sediment may be supplied to the slope from the shelf. By comparing these slope systems, general ideas of slope deposition were developed. Glaciations have a severe impact on slope systems compared to non-glaciated margins and compared to glaciated slopes during pre-glacial times.Dissertation537 223 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Late Quaternary pelagic aragonite preservation in the Arabian Sea and its paleoceanographic implications(2005-12-21); ; ; In the course of the Quaternary the carbon dioxide concentrations of the atmosphere showed large fluctuations related to the oceanic carbon cycle and carbonate system. The production, accumulation, and dissolution of pelagic aragonite constitutes a considerable part of the oceanic carbonate system. Variations in water mass properties, atmospheric and oceanic circulation, which lead to changes in bioproductivity in the upwelling areas influence the preservation of aragonite and therefore the preservation of pteropod shells. This project is concerned with Late Quaternary preservation of pteropods in sediments of the Arabian Sea. To this purpose 15 surface sediment samples and two high resolution sediment cores from the Arabian Sea have been analysed by means of the pteropod shell preservation index LDX (Limacina inflata dissolution index, Gerhard and Henrich, 2001) in respect to the aragonite preservation state. One objective was to test and apply the newly developed LDX on sediments from the Arabian Sea and to trace spatial and temporal variations in pteropod preservation.Dissertation411 113 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Climate and sea level controlled sedimentation processes in two submarine canyons off NW-Africa(2008-11-14); ; ; This study focuses on the trigger mechanisms of gravity-driven sediment transport in two submarine canyons at the passive continental margin off NW-Africa during the past 240 kyr. The sedimentary records allow to determine the turbidite emplacement times based on high resolution age models. The sediment textures of the turbidites were studied by using X-ray radiographies. The sedimentary properties like the terrigenous silt size distribution and XRF-core scanning element data allow to identify the variability of the aeolian dust input in the hemipelagic sediments. These variations can be used to reconstruct the climatic conditions in the hinterland which strongly influence the sediment supply on the shelf. In addition a clay mineral assemblage was used to reconstruct the fluvial input of the West-African rivers.The trigger mechanisms of gravity-driven sediment transport in submarine canyons during sea level changes has been reported from many regions. However, the relationship of sea level changes and short-term climatic events with turbidite deposition is poorly documented. The turbidite history of the Dakar Canyon during the late Quaternary was reconstructed using gravity cores directly recovered from the canyon axis. The highest frequency of turbidite deposition is restricted to the last two major climatic terminations when remobilisation of sediments from the shelf was triggered by eustatic sea level rise. Coarse terrigenous silt size data and high Ti/Ca ratios reflect an overall increased dust supply during the last two peak glacials resulting in the formation of extensive sand seas covering the exposed shelf. The interglacials were characterised by less intensive wind stress. However, sporadic turbidite events coincide with the timing of Heinrich events in the North Atlantic. During these times continental climate has changed rapidly towards increased aridity and enhanced wind strength. This in turn led to a higher dust supply which has fed turbidity currents.The turbidite being deposited during the two main periods of activity consist of sandy to silty sediments. Detailed grain size analyses were used to reconstruct the sedimentary characteristics of these turbidity currents. With increasing distance to the source area a downslope sorting trend in the grain size distribution towards finer grain sizes was observed. A much higher frequency in turbidite activity is recorded during the previous peak glacial in contrast to the last peak glacial. This suggests a higher sediment budget in the source area. The correlation of turbidites is based on their stratigraphic position. A single turbidite can exactly be dated at all core locations in the thalweg. Based on the sedimentological analysis of the turbidites this study provides a schematic model for the sedimentation processes in the Dakar Canyon.The turbidite activity of the Dakar Canyon was then compared to the neighbouring submarine Diola Canyon. Both canyon systems are affected by the seasonal shifts of the Intertropical Convergence Zone. However, the southern Diola Canyon is further influenced by the discharge of the West African rivers. During the late Quaternary a mixture of fluvial derived material and aeolian dust was deposited at the exposed southern Senegalese shelf. Frequent turbidite deposition in the Diola Canyon is recorded during minor sea level rises which forced the remobilisation of this sediment mixture. Furthermore, the post glacial sea level rise removed the remaining sediment deposits from the now flooded shelf region.The results of this PhD study highlight the influence of sea level rise and the subsequent remobilisation of shelf sediments as well as short-lasting climatic changes which act as main factors controlling the sediment flux in the investigated canyon systems.Dissertation1214 388 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Miocene changes in SW-African climate and ocean circulation: inferences from silt analysis and carbonate preservation studies(2006-01-20); ; ; Deep-sea sediments from the SE Atlantic at ODP Sites 1085, 1087 and 1265 off the continental margin SW African and the Walvis Ridge were investigated using sedimentological, mineralogical and geochemical analyses in order to paleoenvironmental and paleoclimatic signals in the Neogene. The variation of carbonate and terrigenous deposition from the Miocene sediment records were associated with changes in the atmospheric circulation pattern. The results showed that the driving process of what so called 'Carbonate Crash' event was complex and differed compared to previous investigation in the other regions. The event in the study area represents a more regional phenomenon. The terrigenous grain-size distribution reveals that the establishment of the wind-driven Benguela Upwelling system and close timing of aridification in South Africa was related to the expansion of the Antarctic ice-sheet and intensification of Southern Hemisphere winds. Variability in carbonate contents are related to the global changes in deep-water chemistry and the variations in southern component of dee-water producing during the interglacial and glacial conditions.Dissertation313 180 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Climate-induced variability of fluvial and aeolian sediment supply and gravity-driven sediment transport off Northwest Africa(2005-02-25); ; ; This study focuses on climate-induced variability in terrigenous sediment supply and gravity-driven sediment transport off NW-Africa during the past 13 kyr. Sediment texture, mainly based on detailed grain-size analysis of the terrigenous silt and fine fraction and modelled end members for aeolian and fluvial supply, was studied on seabed samples recovered from the NW-African continental margin between 17° and 33°N as well as on a high-resolution Holocene sediment record off Morocco to display spatial and temporal variations in dominant sediment transport processes to the Atlantic Ocean and to obtain an overview of the evolution in continental aridity since the last deglaciation. Additional information on the evolution in Holocene NW-African climate and its implications for sediment transport processes is obtained from a high-resolution record of a submarine meandering channel system, the Cap Timiris Canyon, off presently hyperarid Mauritania.Under modern conditions terrigenous sediment supply along the NW-African continental margin north of 29°-30°N is characterized by fluvial discharge to the Atlantic Ocean, whereas further south, sediments are dominantly transported offshore by large dust plumes. During the Early to Mid Holocene relatively humid conditions were prevalent, although (sub-)millennial recurring dry phases are superimposed on this aridity record throughout the Holocene. Further south, off the Sahara desert, gravity-driven sediment transport is also controlled by climate variability during the past 13 kyr. We distinguish two phases of turbidity current activity and relate them to deglacial sea-level rise and Holocene climate variability, respectively. A climate-related coupling to be active for this depositional system during the Holocene is inferred by a (quasi-)periodic turbidity flow pattern and by excluding usually resorted triggers for turbidity current activity within this submarine channel system.Dissertation541 133 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Calcareous nannofossils in the S-Atlantic during the Middle to Late Miocene: Coccolithophorid carbonate budgets, fine-fraction stable isotopes and their paleoceanographic implications(2005-11-17); ; ; The Cenozoic is characterized by major changes in the global climate system from 'greenhouse' conditions in the Early Paleogene towards 'ice-house'-regime in the Neogene. The main object of this study was to document and understand the role of coccolithophores as the main carbonate producers in relation to changes in ocean circulation and global climate between 12.5 and 7.5 Ma. For this purpose ODP Site 1085 and 1092 were investigated. The distribution pattern of single coccolithophorid species, the nannoplankton assemblage composition and the preservation of coccoliths from the eastern S-Atlantic provided the basis for paleoceanographic studies. Additionally, the nannoplankton contribution to the bulk carbonate production as well as the stable isotopic composition of the coccolith carbonate were explored. Many paleoceanographic signals are preserved in coccolithophorid assemblages, and thus, reflect spatial and temporal changes in surface-ocean circulation. The potential of nannofossil stable isotopes as indicators of conditions in the shallow mixed-layer was shown by comparing these records with those of co-existing planktic foraminifers.Dissertation445 131 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, The Senegal mud-belt depocenter (NW-Africa) - an archive for climatic changes, coastal dynamics and shelf organization over the Holocene -(2009-12-21); ; ; NW-Africa, in particular the Sahel region, is very sensitive to climatic changes. Hence, the reconstruction of past climate variability is a valuable way to understand mechanisms of present climatic changes. In front of the Senegal River, in a mid-shelf position, lies a fine-grained depocenter. The investigation of this mud-belt depocenter forms the central theme of this thesis. Mud belts are believed to potentially be natural archives which record such variations. Continental shelves are very dynamic areas where the climatic signal recorded in the sediments may possibly be distorted by several factors.The first phase of this study investigated how the terrigenous fraction of a sediment sequence records past climate variability, specifically, which chemical elements can be employed to reconstruct climate variability off Senegal. We approached this problem with a combination of existing sedimentological techniques to unravel fluvial and aeolian sediment input. The second phase was to reconstruct the hydrological changes occurring during the late Holocene and compare them to several other records from NW-Africa. The third phase was to determine the influence of coastal and paleoclimatic changes on the Senegal mud-belt formation, specifically, to determine to what extent the climatic signal recorded by several sedimentological proxies is disrupted by the coastal changes. Then, the fourth phase of this study involved data collection on the initiation and evolution of the mud belt with the aim of reconstructing the history of this fine-grained shelf depocenter. The new scientific outcomes of this thesis are: (1) the identification of Fe and Al as being the most suitable fluvial proxies off Senegal, implying that specific chemical elements with which to record input variations must be determined for individual regions before climate reconstruction can be performed; (2) the record of two dry periods from 3010 to 2750 cal a BP and from 1900 to 1000 cal a BP, and two main humid periods from 2750 to 1900 cal a BP and from 1000 to 700 cal a BP, provide a better constrained characterization of the climate of late Holocene in this region; (3) the finding that the paleoclimatic signal can be distorted by local hydrological conditions, sediment-remobilizing events and shifts in the river-mouth location, leads to the conclusion that various paleoclimatic records can be erroneous; (4) the history of the mud belt has been reconstructed, increasing our knowledge about the initiation and evolution of these shelfal fine-grained highstand deposits.Dissertation674 212