26 research outputs found
The Late Miocene‐Early Pliocene Biogenic Bloom in the Eastern Equatorial Pacific: New Insights From Integrated Ocean Drilling Program Site U1335
No full textThe late Miocene-early Pliocene “biogenic bloom” (BB) manifests as greatly enhanced biogenic sedimentation in sites along the Equator that has been linked to cooler sea surface temperature (SST) in the eastern equatorial Pacific (EEP). However, the full extent and geometry of the BB in the EEP is less known. To improve on this, we have generated new carbonate content (CaCO3%) and bulk carbonate stable isotope (δ13C and δ18O) records spanning the last 7 Ma at IODP Site U1335, located ca. 5° north of the Equator and to the west of the EEP. Site U1335 δ13C and δ18O records display high-frequency variations coupled to changes in sediment composition and physical properties comparable to patterns seen at on-Equator sites further east. During the late Miocene and the early Pliocene bulk δ18O is higher at Site U1335 compared to two off-Equator sites further east, suggesting cooler SSTs generated by stronger equatorial upwelling reaching northwest of the modern core-equatorial upwelling belt. Enhanced upwelling at Site U1335 is supported by relatively higher sedimentation rates prior to 4.6 Ma, symptomatic of higher biological production during the BB. These observations suggest that during the BB the equatorial upwelling circulation was more focused and less parallel to the Equator compared to present day. </p
(Table S2) Relative abundance of carbonate and biogenic silica particles from IODP Holes 321-U1338A and 321-U1338B
No full text(Table S2) Relative abundance of carbonate and biogenic silica particles from IODP Holes 321-U1338A and 321-U1338
(Table 2) Wet and dry density, settling times and masses from IODP Holes 321-1338A and 321-U1338C
No full text(Table 2) Wet and dry density, settling times and masses from IODP Holes 321-1338A and 321-U1338
(Table 1) Settling times, weights, carbonate concentrations and coarse fraction concentrations from IODP Hole 321-U1338A, 321-U1338B and 321-U1338C
No full text(Table 1) Settling times, weights, carbonate concentrations and coarse fraction concentrations from IODP Hole 321-U1338A, 321-U1338B and 321-U1338
(Table S1) Carbonate concentartions from IODP Holes 321-U1338B
No full text(Table S1) Carbonate concentartions from IODP Holes 321-U1338
Eastern equatorial Pacific bulk sediment properties and paleoceanography since the late Neogene
No full textReconstructing eastern equatorial Pacific (EEP) oceanography since the late Neogene (about 8 million years ago, Ma) is a central topic in current paleoceanographic investigations. The reason for this is two-fold. First, the EEP exerts a strong control on global climate because steep gradients in sea surface temperature (SST) and biological productivity linked to equatorial wind-driven upwelling affect global climate and carbon cycling, including the exchange of upwelled CO2 to the atmosphere. Second, during the last 8 Ma global climate underwent major changes before arriving at its current state, evolving through the last period of widespread global warmth (the early Pliocene) to the colder ‘mean’ global climate state of the pre-industrial world. Deciphering the dynamics of the EEP system since the late Neogene is thus important for understanding how this ocean area works under changing climatic conditions. Despite the large numbers of studies devoted to the EEP, its paleoceanographic evolution since 8 Ma is still debated and contrasting scenarios have often been proposed. This is in part because paleoceanographic reconstructions are challenging in the EEP due to the high environmental, and thus sedimentary, heterogeneity, as well as the extreme seafloor depth, which compromises the preservation of useful foraminiferal archives in many regions. Moreover, some existing legacy data sets are confounded by some basic issues with the way in which the data were collected. Yet, reconstructing properties of surface mixed-layer remains a crucial requirement for deciphering EEP paleoceanography. Fossil foraminifera tests are typically not available for tracing EEP surface ocean properties because of strong sea floor diagenetic alteration. However, calcareous nannofossil carbonate, also produced in the surface mixed layer and accessible in the form of the bulk sedimentary carbonate or sediment ‘fine fraction’, is available. The challenge is to understand what these bulk geochemical signals mean. Bulk sediment comprises a mixture of different, mostly biogenic particles. The information carried by its properties, including physical and geochemical signals, comprises a mixed signal reflecting different ecological, metabolic and depositional processes associated with the formation and sedimentation of the various calcite particles. The purpose of this thesis is to understand what bulk sediment records represent in terms meaningful for deciphering the paleoceanographic history of the EEP. The results add to, and significantly improve the paleoceanographic “tool box” available for developing proxy records in this complex oceanic region. This thesis comprises a kappa, two published papers and a manuscript, in review as this is written (April 2019). Paper I examines the factors linking sediment composition and physical properties in the EEP through analysis of the relationship between sediment carbonate content and sediment density. Paper II and Paper III focuses on improving the understanding of bulk carbonate carbon and oxygen stable isotope signals by disentangling the contribution of different carbonate components. In these studies, a multiproxy approach was adopted to reconstruct ocean evolution of the EEP since the late Miocene. A major conclusion is that bulk carbonate stable isotopes reflect the isotopic composition of calcareous nannofossils, and therefore surface water conditions, despite complication by several factors. The ideas and findings of the latter two papers have been further tested in an unpublished inter-basin comparison presented in the Chapter 6 of this kappa. The findings of this doctoral thesis demonstrate that bulk sediment is more than just a correlation tool and can provide a reliable indicator of surface ocean conditions that can be used to decipher EEP oceanographic history since 8 Ma. At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p
Paleoclimatic and paleoenvironmental history of the Lower Pleistocene interval in the Crosia-Calopezzati Basin (Ionian Calabria Southern Italy) = Ricostruzione paleoclimatica e paleoambientale del Pleistocene inferiore del bacino di Crosia â Calopezzati (Calabria ionica, Italia meridionale) .
No full textPaleoceanography of the Eastern Equatorial Pacific over the last eight million years
No full textMany studies have investigated the evolution of the Eastern Equatorial Pacific (EEP) Ocean paleoceanography since the late Neogene because of its role in regulating the Earth’s climate and because global climate has undergone major changes during this time period. However, current understanding of the EEP paleoceanography encounters two basic problems. First, this region is characterized by steep east-west and meridional gradients in Sea Surface Temperatures (SSTs) and biological productivity, which can vary from one year to another. Second, the seafloor lies below the lysocline in most of the area, leading to poor preservation of biogenic carbonate. As a result, sediments from the EEP exhibit major changes in their physical and compositional properties over short time, and hence sediment depth, increments. Therefore, the study of bulk sediment properties is crucial to further understand the paleoceanography of EEP during the past 8 Myr. Bulk sediment properties are highly appropriate proxies for achieving highly resolved and time comparable SST and biological productivity data because changes in such properties can be traced across the EEP over large distances.This thesis presents two manuscripts. In Paper 1 we examine the positive second-order relationship between wet bulk density (WBD) and carbonate content of sediments from the EEP. This relationship is important because it can be used to determine high-resolution carbonate content records. In Paper 2 we examine bulk sediment stable isotopes records from the EEP to understand what these records actually represent and whether these records are robust across the EEP. The main conclusions of these studies are (1) a single two-component equation cannot be used to determine carbonate content from the WBD. Instead, the WBD-carbonate relationship can only be described by an infinite series of curves representing the mixing of different components; (2) bulk sediment stable isotope records are robust across the EEP and changes in grain-size are not the primary cause of variations of these records.Reconstructing the Oceanography of the Climatically Sensitive Low-Latitude Pacific Ocean Since the Late Miocen
CATHEPSIN-K IS A SENSITIVE IMMUNOHISTOCHEMICAL MARKER FOR DETECTION OF MICRO-GRANULOMAS IN HYPERSENSITIVITY PNEUMONITIS
No full textHypersensitivity Pneumonitis (HP) is an interstitial lung disease that occurs upon exposure to a variety of inhaled organic antigens. The presence of small non-caseating granulomas and isolated giant cells is not specific, but is considered a relevant histological feature for HP. The detection of granulomas is widely considered as easy on standard histological stains, but microgranuloma detection can be difficult and/or time consuming, especially in chronic HP cases. Cathepsin K (Cath-K) is a potent cysteine protease expressed at high levels in activated macrophages (osteoclasts, and epithelioid cells in granulomas), but is not expressed in resident macrophages thus representing a promising marker to rapidly detect and quantitatively evaluate micro-granulomas in interstitial lung diseases. We analyzed the expression of Cath-K by immunohistochemistry in 22 subacute and chronic HP cases, using semi-quantitative scores. Control samples included normal lung tissue, and a variety of interstitial lung diseases: 3 Wegener's granulomatosis, 3 saxcoidosis, 3 tuberculosis, 1 berylliosis, 20 idiopathic pulmonary fibrosis (IPF), 2 Langerhans' cell histiocytosis, 5 nonspecific-interstitial pneumonia (NSIP), 5 cryptogenic organising-pneumonia (COP), 2 Airway-Centered Interstitial Fibrosis (ACIF), 5 desquamative interstitial pneumonia (DIP), 3 respiratory bronchiolitis interstitial lung disease (RB-ILD). Intense expression of Cath-K was demonstrated in epithelioid and giant cells in all cases containing granulomas (HP, sarcoidosis, Wegener's granulomatosis, berylliosis, tuberculosis). Among HP cases 19/22 (86,3%) contained granulomas that could be semiquantitatively evaluated. In all HP and control cases alveolar macrophages did not express Cath-K, including cases characterised by large collections of alveolar macrophages such as DIP and RB-ILD. Conclusions: Cath-K represents a sensitive and specific marker to detect and quantitate granulomatous reactions in interstitial lung diseases, and is particularly useful in chronic HP cases. (Sarcoidosis Vasc Diffuse Lung Dis 2010; 27: 57-63
X-ray fluorescence data from Contessa Road (Italy), Paleocene-Eocene Thermal Maximum interval
No full textThe Paleocene-Eocene Thermal Maximum (PETM) is the most studied global warming event of a series of Paleocene-Eocene carbon cycle perturbations called hyperthermals. PETM origins have been associated with volcanic-related carbon emissions; however, other carbon cycle feedbacks were required to develop a large hyperthermal such as the PETM. The orbital configuration in which the PETM occurred is still unclear despite possible orbital controls on the PETM triggering. This dataset contains X-Ray Fluorescence (XRF) data (Fe, Ca, and Si) from Contessa Road (Italy), a sedimentary section with reduced calcium carbonate dissolution compared to deep ocean sites. Astrochronological age models and probabilistic assessments reveal that the PETM onset appeared close to both short and long eccentricity maxima, which suggests that orbitally controlled insolation variations may have thermally destabilized carbon reservoirs that worked as PETM positive carbon cycle feedbacks
