Details
| Originalsprache | Englisch |
|---|---|
| Qualifikation | Doctor rerum naturalium |
| Gradverleihende Hochschule | |
| Betreut von |
|
| Datum der Verleihung des Grades | 3 Dez. 2018 |
| Erscheinungsort | Hannover |
| Publikationsstatus | Veröffentlicht - 2018 |
Abstract
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Hannover, 2018. 132 S.
Publikation: Qualifikations-/Studienabschlussarbeit › Dissertation
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TY - BOOK
T1 - Carbonate sedimentology and chemostratigraphy of Kimmeridgian shoal-water deposits in the Lower Saxony Basin of Northern Germany
AU - Zuo, Fanfan
N1 - Doctoral thesis
PY - 2018
Y1 - 2018
N2 - The Late Jurassic is generally considered to be an equable greenhouse-type climate with a high global sea level. Within the Late Jurassic, the Kimmeridgian stage represents a temperature plateau, reaching peak warmth. During this period, large parts of Europe were covered by shallow epicontinental seas with widespread deposition of subtropical shoal-water carbonates. Unfortunately, the absence of open-marine marker fossils hampers a precise age assignment of these Kimmeridgian strata. In addition, the fragmentary shoal-water record with numerous sedimentary gaps makes the stratigraphic correlation notoriously difficult on both regional and global scales. These stratigraphic uncertainties limit further interpretation of the significant paleoclimatic signals derived from these deposits. This thesis focuses on the Kimmeridgian deposits in the Lower Saxony Basin (LSB), which are composed of alternating limestone, marl and claystone, representing the typical Kimmeridgian platform deposits as mentioned above. In order to refine the age assignment of these strata, an integrated stratigraphic approach, combining chemostratigraphic (carbon and strontium isotopes) analyses with conventional sequence stratigraphy and biostratigraphy, is applied to three sections (Langenberg, Bisperode, Pötzen). Moreover, oxygen isotope analyses based on pristine low-Mg calcite shell material, together with clay mineral assemblages, provide novel insight into the paleoclimatic evolution for the Kimmeridgian world. In order to provide a robust baseline for further stratigraphic correlation and paleoclimatic interpretation, analysis of high-resolution carbonate microfacies and sequence stratigraphy are firstly carried out. Based on the regional ostracod biostratigraphic framework, the established sequences can be correlated between the studied sections in a regional scale, which allows for a better understanding of the main factors controlling the Kimmeridgian sedimentary evolution in the LSB. Moreover, a preliminary sequence stratigraphic correlation with other European basins reveals that the majority of the medium-scale sequence boundaries can be recognized in similar biostratigraphic positions in other areas. Furthermore, a precise dating of the Kimmeridgian deposits in the LSB is performed, combining the conventional ostracod biostratigraphy and strontium isotope stratigraphy (SIS). The new strontium data presented here confirm the potential of well-preserved low-Mg calcite from shallow-marine settings to preserve global marine Sr-isotope signals and expand the limited SIS dataset of the Kimmeridgian. In addition, after strict evaluation of both diagenetic alternation and local environmental effects, the δ13C signatures from different sections are considered to predominantly record the global marine signals. A high-resolution composite δ13C record for Kimmeridgian shoal-water deposits can therefore be established, calibrated by the newly established dating results. Consequently, the new chemostratigraphic results allow for a stratigraphic correlation between shallow-marine deposits in the Subboreal LSB and coeval pelagic counterparts in the peri-Tethyan and Western Tethyan realms. Shell materials precipitated by brachiopods, oysters and Trichites shells from the LSB are evaluated for their potential to act as archive for marine sea surface temperatures (SST). An overall slightly warming trend from the early to late Kimmeridgian is revealed according to the established SST curve, and a weak seasonality in SST is documented by δ18O variations along a large Trichites shell. However, a special “cold” snap inferred from distinctly higher δ18O values in the early Kimmeridgian is interpreted to be partly related to the short-term influx of cooler boreal water masses. This positive oxygen isotope anomaly may also be partly linked to enhanced δ18Oseawater values driven by a drier climate, which is inferred from the smectite-dominated characteristic of the coeval bulk material. Moreover, the kaolinite/(illite+chlorite) ratio points out humid/arid fluctuations correlate well with sea-level changes, with humid climates accompanying high sea-levels and arid climates accompanying low sea-levels.
AB - The Late Jurassic is generally considered to be an equable greenhouse-type climate with a high global sea level. Within the Late Jurassic, the Kimmeridgian stage represents a temperature plateau, reaching peak warmth. During this period, large parts of Europe were covered by shallow epicontinental seas with widespread deposition of subtropical shoal-water carbonates. Unfortunately, the absence of open-marine marker fossils hampers a precise age assignment of these Kimmeridgian strata. In addition, the fragmentary shoal-water record with numerous sedimentary gaps makes the stratigraphic correlation notoriously difficult on both regional and global scales. These stratigraphic uncertainties limit further interpretation of the significant paleoclimatic signals derived from these deposits. This thesis focuses on the Kimmeridgian deposits in the Lower Saxony Basin (LSB), which are composed of alternating limestone, marl and claystone, representing the typical Kimmeridgian platform deposits as mentioned above. In order to refine the age assignment of these strata, an integrated stratigraphic approach, combining chemostratigraphic (carbon and strontium isotopes) analyses with conventional sequence stratigraphy and biostratigraphy, is applied to three sections (Langenberg, Bisperode, Pötzen). Moreover, oxygen isotope analyses based on pristine low-Mg calcite shell material, together with clay mineral assemblages, provide novel insight into the paleoclimatic evolution for the Kimmeridgian world. In order to provide a robust baseline for further stratigraphic correlation and paleoclimatic interpretation, analysis of high-resolution carbonate microfacies and sequence stratigraphy are firstly carried out. Based on the regional ostracod biostratigraphic framework, the established sequences can be correlated between the studied sections in a regional scale, which allows for a better understanding of the main factors controlling the Kimmeridgian sedimentary evolution in the LSB. Moreover, a preliminary sequence stratigraphic correlation with other European basins reveals that the majority of the medium-scale sequence boundaries can be recognized in similar biostratigraphic positions in other areas. Furthermore, a precise dating of the Kimmeridgian deposits in the LSB is performed, combining the conventional ostracod biostratigraphy and strontium isotope stratigraphy (SIS). The new strontium data presented here confirm the potential of well-preserved low-Mg calcite from shallow-marine settings to preserve global marine Sr-isotope signals and expand the limited SIS dataset of the Kimmeridgian. In addition, after strict evaluation of both diagenetic alternation and local environmental effects, the δ13C signatures from different sections are considered to predominantly record the global marine signals. A high-resolution composite δ13C record for Kimmeridgian shoal-water deposits can therefore be established, calibrated by the newly established dating results. Consequently, the new chemostratigraphic results allow for a stratigraphic correlation between shallow-marine deposits in the Subboreal LSB and coeval pelagic counterparts in the peri-Tethyan and Western Tethyan realms. Shell materials precipitated by brachiopods, oysters and Trichites shells from the LSB are evaluated for their potential to act as archive for marine sea surface temperatures (SST). An overall slightly warming trend from the early to late Kimmeridgian is revealed according to the established SST curve, and a weak seasonality in SST is documented by δ18O variations along a large Trichites shell. However, a special “cold” snap inferred from distinctly higher δ18O values in the early Kimmeridgian is interpreted to be partly related to the short-term influx of cooler boreal water masses. This positive oxygen isotope anomaly may also be partly linked to enhanced δ18Oseawater values driven by a drier climate, which is inferred from the smectite-dominated characteristic of the coeval bulk material. Moreover, the kaolinite/(illite+chlorite) ratio points out humid/arid fluctuations correlate well with sea-level changes, with humid climates accompanying high sea-levels and arid climates accompanying low sea-levels.
U2 - 10.15488/4155
DO - 10.15488/4155
M3 - Doctoral thesis
CY - Hannover
ER -