- Email: [email protected]
Modeling Changes in the Nitrogen Cycle and its Isotopes in the Modern and Glacial Ocean
458
Abstracts / Quaternary International 279-280 (2012) 346–461
TOOTH MESOWEAR AND TOOTH MICROWEAR: ASSESSING DIETS IN HERBIVOROUS UNGULATES
METHODS
FOR
INITIATION OF CHANGJIANG (YANGTZE) DELTA: IMPLICATION FROM SEDIMENTARY FACIES, RADIOCARBON DATES AND FOSSILS INFORMATION OF THE CORES PK01 AND XJ03
Nikos Solounias. New York College of Osteopathic Medicine, United States E-mail address: [email protected]
Bing Song. State Key Laboratory of Estuarine & Coastal Resear, China E-mail address: [email protected]
The paleoecology of Pleistocene species is usually thought to be well known compared to older fossil taxa because, in general, they are more similar to their extant relatives. However, recent advances in dietary paleoecology using environmental proxies such as stable isotopes or tooth wear analyses, have revealed a great degree of ecological variation and complexity for many species during this time period. Tooth microwear and mesowear methods in particular have improved our knowledge of Pleistocene ungulate ecology and have revealed details about the environmental context of human evolution. The purpose of this presentation is to describe these methodologies and illustrate their utility through a few selected examples. Tooth mesowear is the evaluation of the wear of molar apices of artiodactyls and perissodactyls and the macroscopic wear of teeth and apices is the result of both attrition and abrasion. These two forces occur at all times, the result of which is assessed through the macroscopic observation of cusp relief and shape. Tooth microwear examines pits and scratches that vegetation leaves on enamel. High resolution epoxy tooth casts are examined with a stereomicroscope. The number of scratches and pits, and other topographical scars are evaluated and counted. Comparisons of unknown species with a microwear database of species with known diets are used to assess the diet of fossil taxa. Both methods can be performed on a sample to get two independent assessments that represent two different temporal scales. However, microwear reflects diet on a shorter timeframe than mesowear, perhaps days or even hours before the death of the animal. Thus, microwear reflects the local and seasonal ecological context and gives the evaluator more greater specificity to dietary assignments. MODELING CHANGES IN THE NITROGEN CYCLE AND ITS ISOTOPES IN THE MODERN AND GLACIAL OCEAN Christopher Somes. IFM-GEOMAR, Germany E-mail address: [email protected]
Fixed nitrogen (fixed-N) is one of the major limiting nutrients throughout the present-day oceans and regulates the efficiency to which marine phytoplankton take up atmospheric CO2 and transport it to the deep ocean and sea-surface sediments via their sinking detrital matter, a mechanism known as the biological pump. The main sink and source processes of the oceanic N budget are denitrification/anammox and N2 fixation, respectively, and how tightly these processes are coupled will determine the balance of the oceanic N budget. Diazotrophs (microorganisms capable of N2 fixation) have high iron (Fe) requirements and may be dependent on atmospheric Fe deposition to grow in the stratified oligotrophic ocean, which could decouple N2 fixation from denitrification. N isotope sediment records in present-day suboxic zones (e.g., Eastern Tropical North/South Pacific, Arabian Sea) suggest increased denitrification during the last deglacitaion, while records in the tropical North Atlantic (where N2 fixation occurs) are interpreted as increased N2 fixation, but may have a time lag of w5,000 years after denitrification. This could result in a smaller oceanic fixed-N inventory as well as a decrease in the strength biological pump, which could contribute to rising atmospheric CO2. We investigate this response using an Earth System Climate Model that includes N isotopes by applying glacial boundary conditions, including atmospheric Fe limitation of N2 fixation sensitivity experiments, and show that the model can reproduce the N isotope trends of observations in these regions. Our results suggest that the N inventory could have been as much as 9% higher or more in the glacial ocean because changes in N2 fixation respond more slowly than denitrification, largely in part to reduced benthic denitrification (due to lower sea level and more exposed continental shelves), which can occur at high latitudes where N2 fixation cannot efficiently balance this N loss, as opposed to water column denitrification in the tropical oceans.
Abstract: The Changjiang (Yangtze) delta, in the eastern China, is one of the largest tidal-dominated deltas in the world. In order to get the information on its initiation, we obtained two sediment cores of PK01 and XJ03 in the uppermost part of the delta. Based on sediment composition, grain size, texture, faunal content, and AMS 14C age, we find two sediment systems: (1) estuary depositional system including tidal-fluvial and flood plain, and (2) delta depositional system consisting of delta front, lower intertidal to subtidal flat, upper intertidal flat and surface soil. The estuary depositonal system was mainly distributed in the west of Nanjing city about 12-4 cal. kyr BP and the middle of Yizhen city and Yangzhou city about 12-8.4 cal. kyr BP. The delta depositional system was mainly distributed in the middle of Yizhen city and Yangzhou city about 7.4-4 cal. kyr BP. According to the sediment information and isochronal line, we can infer that the initiation of the delta at Yizhen and the maximum flooding surface (MxFS) occurred on the span of 8.0-7.4 cal. kyr BP. POLYGENETIC DEFORMATION RESULTING FROM INTERACTION OF KARSTIC, DIAPIRIC AND TECTONIC PROCESSES IN EARLY PLEISTOCENE SEDIMENTS OF THE CENTRAL EBRO BASIN (SPAIN) María Asunción Soriano. Universidad de Zaragoza, Spain E-mail address: [email protected]
Deformation of Quaternary sediments of the Ebro Basin is usually attributed to evaporite dissolution. Active karst subsidence is both a conspicuous geomorphic feature and a first-order natural hazard in the area, indeed. However, detailed studies of sedimentology and structure of Early Pleistocene deposits evidence deformation of diverse origins. The sedimentary series is composed of fluvial gravels with scarce interbedded sands and minor lutites. They represent a gravel braided fluvial system dominated by low-relief longitudinal bars and shallow channels. Internal angular unconformities separate a number of stratigraphic units. Normal faults, making conjugate systems in some cases, are frequent deformation structures. Most of them show N-S to NNW-SSE strike that is consistent with the regional stress field. There are also positive structures identified as diapirs, with a core of Neogene marls partially piercing the Quaternary cover, as well as reverse faults, sharp monoclines, and melanges of gravel and marl associated to them. Finally, there are narrow tubular features with unstructured infill that disrupt the rest of the Quaternary sediments, which are interpreted as karst conduits. Interaction between distinct deformation processes is evidenced in various ways. Some boundaries of diapirs and karst structures are controlled by faults, suggesting that the tectonic structure has locally triggered either migration of plastic marls or karstic subsidence. The most striking surveyed structure is a karst-collapse feature bounded by a tectonic nearvertical fault at its western margin, and by progressive unconformities, small reverse faults and asymmetric folds at the eastern one, showing synsedimentary subsidence. In summary, not only karstification but also interaction with tectonics and diapirism occurred throughout Early Pleistocene times in the Ebro Basin. Probable feedback between them should be considered while Quaternary sedimentation was in progress. RECONSTRUCTION OF QUATERNARY LANDSCAPE EVOLUTION BASED ON 10BE DENUDATION RATES AND TECTONIC UPLIFT DATA IN A MODERATE UPLIFTED REGION (ARDENNES MASSIF, BELGIUM) Nicolas Sougnez. Université Catholique de Louvain, Belgium E-mail address: [email protected]
This research focuses on the relations between past tectonic activity and long term erosion rates for a region with moderate relief, the Belgian Ardennes Massif. This region is well known for having been subject to
Abstracts / Quaternary International 279-280 (2012) 346–461
TOOTH MESOWEAR AND TOOTH MICROWEAR: ASSESSING DIETS IN HERBIVOROUS UNGULATES
METHODS
FOR
INITIATION OF CHANGJIANG (YANGTZE) DELTA: IMPLICATION FROM SEDIMENTARY FACIES, RADIOCARBON DATES AND FOSSILS INFORMATION OF THE CORES PK01 AND XJ03
Nikos Solounias. New York College of Osteopathic Medicine, United States E-mail address: [email protected]
Bing Song. State Key Laboratory of Estuarine & Coastal Resear, China E-mail address: [email protected]
The paleoecology of Pleistocene species is usually thought to be well known compared to older fossil taxa because, in general, they are more similar to their extant relatives. However, recent advances in dietary paleoecology using environmental proxies such as stable isotopes or tooth wear analyses, have revealed a great degree of ecological variation and complexity for many species during this time period. Tooth microwear and mesowear methods in particular have improved our knowledge of Pleistocene ungulate ecology and have revealed details about the environmental context of human evolution. The purpose of this presentation is to describe these methodologies and illustrate their utility through a few selected examples. Tooth mesowear is the evaluation of the wear of molar apices of artiodactyls and perissodactyls and the macroscopic wear of teeth and apices is the result of both attrition and abrasion. These two forces occur at all times, the result of which is assessed through the macroscopic observation of cusp relief and shape. Tooth microwear examines pits and scratches that vegetation leaves on enamel. High resolution epoxy tooth casts are examined with a stereomicroscope. The number of scratches and pits, and other topographical scars are evaluated and counted. Comparisons of unknown species with a microwear database of species with known diets are used to assess the diet of fossil taxa. Both methods can be performed on a sample to get two independent assessments that represent two different temporal scales. However, microwear reflects diet on a shorter timeframe than mesowear, perhaps days or even hours before the death of the animal. Thus, microwear reflects the local and seasonal ecological context and gives the evaluator more greater specificity to dietary assignments. MODELING CHANGES IN THE NITROGEN CYCLE AND ITS ISOTOPES IN THE MODERN AND GLACIAL OCEAN Christopher Somes. IFM-GEOMAR, Germany E-mail address: [email protected]
Fixed nitrogen (fixed-N) is one of the major limiting nutrients throughout the present-day oceans and regulates the efficiency to which marine phytoplankton take up atmospheric CO2 and transport it to the deep ocean and sea-surface sediments via their sinking detrital matter, a mechanism known as the biological pump. The main sink and source processes of the oceanic N budget are denitrification/anammox and N2 fixation, respectively, and how tightly these processes are coupled will determine the balance of the oceanic N budget. Diazotrophs (microorganisms capable of N2 fixation) have high iron (Fe) requirements and may be dependent on atmospheric Fe deposition to grow in the stratified oligotrophic ocean, which could decouple N2 fixation from denitrification. N isotope sediment records in present-day suboxic zones (e.g., Eastern Tropical North/South Pacific, Arabian Sea) suggest increased denitrification during the last deglacitaion, while records in the tropical North Atlantic (where N2 fixation occurs) are interpreted as increased N2 fixation, but may have a time lag of w5,000 years after denitrification. This could result in a smaller oceanic fixed-N inventory as well as a decrease in the strength biological pump, which could contribute to rising atmospheric CO2. We investigate this response using an Earth System Climate Model that includes N isotopes by applying glacial boundary conditions, including atmospheric Fe limitation of N2 fixation sensitivity experiments, and show that the model can reproduce the N isotope trends of observations in these regions. Our results suggest that the N inventory could have been as much as 9% higher or more in the glacial ocean because changes in N2 fixation respond more slowly than denitrification, largely in part to reduced benthic denitrification (due to lower sea level and more exposed continental shelves), which can occur at high latitudes where N2 fixation cannot efficiently balance this N loss, as opposed to water column denitrification in the tropical oceans.
Abstract: The Changjiang (Yangtze) delta, in the eastern China, is one of the largest tidal-dominated deltas in the world. In order to get the information on its initiation, we obtained two sediment cores of PK01 and XJ03 in the uppermost part of the delta. Based on sediment composition, grain size, texture, faunal content, and AMS 14C age, we find two sediment systems: (1) estuary depositional system including tidal-fluvial and flood plain, and (2) delta depositional system consisting of delta front, lower intertidal to subtidal flat, upper intertidal flat and surface soil. The estuary depositonal system was mainly distributed in the west of Nanjing city about 12-4 cal. kyr BP and the middle of Yizhen city and Yangzhou city about 12-8.4 cal. kyr BP. The delta depositional system was mainly distributed in the middle of Yizhen city and Yangzhou city about 7.4-4 cal. kyr BP. According to the sediment information and isochronal line, we can infer that the initiation of the delta at Yizhen and the maximum flooding surface (MxFS) occurred on the span of 8.0-7.4 cal. kyr BP. POLYGENETIC DEFORMATION RESULTING FROM INTERACTION OF KARSTIC, DIAPIRIC AND TECTONIC PROCESSES IN EARLY PLEISTOCENE SEDIMENTS OF THE CENTRAL EBRO BASIN (SPAIN) María Asunción Soriano. Universidad de Zaragoza, Spain E-mail address: [email protected]
Deformation of Quaternary sediments of the Ebro Basin is usually attributed to evaporite dissolution. Active karst subsidence is both a conspicuous geomorphic feature and a first-order natural hazard in the area, indeed. However, detailed studies of sedimentology and structure of Early Pleistocene deposits evidence deformation of diverse origins. The sedimentary series is composed of fluvial gravels with scarce interbedded sands and minor lutites. They represent a gravel braided fluvial system dominated by low-relief longitudinal bars and shallow channels. Internal angular unconformities separate a number of stratigraphic units. Normal faults, making conjugate systems in some cases, are frequent deformation structures. Most of them show N-S to NNW-SSE strike that is consistent with the regional stress field. There are also positive structures identified as diapirs, with a core of Neogene marls partially piercing the Quaternary cover, as well as reverse faults, sharp monoclines, and melanges of gravel and marl associated to them. Finally, there are narrow tubular features with unstructured infill that disrupt the rest of the Quaternary sediments, which are interpreted as karst conduits. Interaction between distinct deformation processes is evidenced in various ways. Some boundaries of diapirs and karst structures are controlled by faults, suggesting that the tectonic structure has locally triggered either migration of plastic marls or karstic subsidence. The most striking surveyed structure is a karst-collapse feature bounded by a tectonic nearvertical fault at its western margin, and by progressive unconformities, small reverse faults and asymmetric folds at the eastern one, showing synsedimentary subsidence. In summary, not only karstification but also interaction with tectonics and diapirism occurred throughout Early Pleistocene times in the Ebro Basin. Probable feedback between them should be considered while Quaternary sedimentation was in progress. RECONSTRUCTION OF QUATERNARY LANDSCAPE EVOLUTION BASED ON 10BE DENUDATION RATES AND TECTONIC UPLIFT DATA IN A MODERATE UPLIFTED REGION (ARDENNES MASSIF, BELGIUM) Nicolas Sougnez. Université Catholique de Louvain, Belgium E-mail address: [email protected]
This research focuses on the relations between past tectonic activity and long term erosion rates for a region with moderate relief, the Belgian Ardennes Massif. This region is well known for having been subject to