Search

The Carbonate Compensation Depth (CCD) refers to the depth within the ocean where the production and dissolution rates of carbonates reach equilibrium, widely likened to the oceanic calcareous 'snowline'. The reconstruction of deep-time CCD has significant implications for understanding ocean circulation, seawater chemical conditions, sediment distribution, and the surface carbon cycle. This paper critically reviews the methods for CCD reconstruction, summarizes the driving mechanisms of the Cenozoic CCD evolution and its association with the carbon cycle, and offers insights into future directions for CCD research. CCD reconstruction has evolved over the past half century from early qualitative to quantitative methods. These methodological improvements have markedly improved the accuracy and resolution of CCD. Existing studies have indicated a general trend of the CCD deepening across major ocean basins since the Cenozoic, interspersed with a minor shallowing phase during the mid-Miocene. The variations in the CCD are primarily influenced by factors such as ocean productivity, weathering, and shelf-basin partitioning. During climate events such as the Paleocene-Eocene Thermal Maximum, the CCD exhibits pulselike fluctuations. Future research should focus on precision and quantification while integrating model simulations to further explore the correlations and response mechanisms between the CCD and the paleoclimate as well as the carbon cycle. [ABSTRACT FROM AUTHOR]

This is the first high-resolution seismic study showing how the Chicxulub impact shaped the eastern slope of the Campeche Bank in the south-eastern Gulf of Mexico. The induced shock wave fractured Cretaceous strata causing the collapse of the upper slope and shelf over a length of ca. 200 km. Failed material was either transported downslope or remained in parts on the accommodation space created by the collapsed. In the Cenozoic, the East Campeche Plastered Drift developed within the created accommodation space, controlled by the inflowing surface current from the Caribbean, which forms the Loop Current. The internal reflection configuration of the drift shows that the closure of the Suwannee Strait in the Late Oligocene and the closure of the CAS in the Mid to Late Miocene controlled the variability of the southern Loop Current in time. Since the Loop Current transports heat and moisture from the western Atlantic warm water pool into the North Atlantic and further to NW Europe by the Gulf Stream, the drift represents an archive for controlling factors that influenced climate of the northern hemisphere. This first high-resolution seismic reflection study from the eastern Campeche Bank expands the understanding of destructive processes that a meteorite impact induces into the earth system. Furthermore, these data document that the East Campeche Plastered Drift bears the potential to understand the link between the climate variability of the northern hemisphere and oceanic processes in the equatorial western Atlantic. [ABSTRACT FROM AUTHOR]

This paper briefly introduces the conception and research history of the Great Oxidation Event (GOE) in the early Paleoproterozoic and summarizes the primary geological and geochemical records of this event. On the basis of these, we overview the significant progress in three fields of the GOE: the timing and process of its startup, its mechanisms, and its climatic-ecological effects. The records of mass-independent fractionation of sulfur isotopes suggest that the startup of the GOE might be multi-episodic, which is obviously inconsistent with the single-episodic opinion obtained from atmospheric model simulations. The fundamental mechanism of the GOE was the source of the atmospheric O2 exceeding the sink, but it remains uncertain whether it was due to the increase in the source or the decrease in the sink. The GOE substantially affected the climate, biological evolution, and biogeochemical cycles, but the specific processes remain elusive. In consideration of the current progress, we propose four aspects for future explorations, including the construction of geological and geochemical proxies for extremely low atmospheric oxygen content (pO2), how the GOE changed the evolutions of Earth's habitability and the processes in deep Earth, and constraining the mechanism of the GOE by coupling geological events with different time scales. [ABSTRACT FROM AUTHOR]

The Late Miocene global cooling (LMGC; approximately 7.9–5.8 Ma) was associated with remarkable changes in monsoon dynamics, biogenic bloom in the global oceans, and the rise of modern ecosystems at the expense of old biota. However, the possible linkage between the environmental changes and ecosystem shifts during the LMGC is still debated. In this paper, we show the high-resolution changes in the fluxes of selected radiolarian species, suggesting a drastic reorganization in the paleoceanography and ecosystem in the Japan Sea during the LMGC. The endemic radiolarian Cycladophora nakasekoi dominated the Japan Sea until 7.4 Ma when the Japan Sea sediment changed from dark radiolarian-rich sediment to organic-poor diatom ooze. Changes in the fluxes of C. nakasekoi and Tricolocapsa papillosa, the latter related to changes in the Pacific central water (PCW), show 100, 200, and ~ 500 ka cycles with their high flux mostly within the darker sediment intervals during the low-eccentricity period until 7.4 Ma, suggesting that orbitally paced PCW inflow might have been the major nutrient source into the Japan Sea. At about 7.4 Ma, these species decreased at the expense of increased Larcopyle weddellium, a radiolarian related to the North Pacific intermediate water (NPIW), and Cycladophora sphaeris, a subarctic radiolarian species, implying a decrease in PCW inflow and an increase in the inflow of NPIW and subarctic shallow water. Such a change would have been related to the LMGC-induced weakening in the Pacific Meridional overturning circulation and the southward shift of the subarctic front due to intensified East Asian winter monsoon. Such a drastic reorganization in the hydrography in the Japan Sea probably caused changes in nutrient provenance from the PCW to the NPIW and resulted in faunal turnover, marked by the disappearance of the old regional and endemic faunal components, such as C. nakasekoi. [ABSTRACT FROM AUTHOR]