Gehler, Alexander

[["dc.bibliographiccitation.firstpage","306"],["dc.bibliographiccitation.journal","Geochimica et Cosmochimica Acta"],["dc.bibliographiccitation.lastpage","317"],["dc.bibliographiccitation.volume","102"],["dc.contributor.author","Pack, Andreas"],["dc.contributor.author","Gehler, Alexander"],["dc.contributor.author","Suessenberger, Annette"],["dc.date.accessioned","2018-11-07T09:28:51Z"],["dc.date.available","2018-11-07T09:28:51Z"],["dc.date.issued","2013"],["dc.description.abstract","Fluctuations in atmospheric p(CO2) may have played the key role in global climate throughout Earth's history. For the quantification of past variations in atmospheric p(CO2), several geological proxy approaches and geochemical models have been developed. Here, we evaluate a new CO2 proxy approach that is based on the triple oxygen isotope composition (O-16, O-17, O-18) of skeletal apatite of terrestrial mammals. Our approach utilizes the relation between an anomaly in O-17 of tropospheric air O-2 and atmospheric p(CO2). The anomaly is transferred from inhaled air O-2 to skeletal apatite of mammals. Hence, triple oxygen isotope data of mammalian bioapatite provide information regarding p(CO2) during the animal's lifetime. The approach was calibrated with a detailed mass balance model that was verified by analyses on a set of recent mammals. We evaluate the potential of this new independent terrestrial paleo-CO2 proxy in a case study including Eocene to Miocene samples. The present investigation provides promising results that are in good agreement with existing proxy- and model data. The uncertainty intrinsic to the proxy is mainly due to uncertainties in physiological parameters. (C) 2012 Elsevier Ltd. All rights reserved."],["dc.description.sponsorship","German National Science Foundation DFG [PA909/5-1]"],["dc.identifier.doi","10.1016/j.gca.2012.10.017"],["dc.identifier.isi","000313202300018"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/30881"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0016-7037"],["dc.title","Exploring the usability of isotopically anomalous oxygen in bones and teeth as paleo-CO2-barometer"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","7739"],["dc.bibliographiccitation.issue","28"],["dc.bibliographiccitation.journal","PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA"],["dc.bibliographiccitation.lastpage","7744"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Gehler, Alexander"],["dc.contributor.author","Gingerich, Philip D."],["dc.contributor.author","Pack, Andreas"],["dc.date.accessioned","2018-11-07T10:11:39Z"],["dc.date.available","2018-11-07T10:11:39Z"],["dc.date.issued","2016"],["dc.description.abstract","The Paleocene-Eocene Thermal Maximum (PETM) is a remarkable climatic and environmental event that occurred 56 Ma ago and has importance for understanding possible future climate change. The Paleocene-Eocene transition is marked by a rapid temperature rise contemporaneous with a large negative carbon isotope excursion (CIE). Both the temperature and the isotopic excursion are well-documented by terrestrial and marine proxies. The CIE was the result of a massive release of carbon into the atmosphere. However, the carbon source and quantities of CO2 and CH4 greenhouse gases that contributed to global warming are poorly constrained and highly debated. Here we combine an established oxygen isotope paleothermometer with a newly developed triple oxygen isotope paleo-CO2 barometer. We attempt to quantify the source of greenhouse gases released during the Paleocene-Eocene transition by analyzing bioapatite of terrestrial mammals. Our results are consistent with previous estimates of PETM temperature change and suggest that not only CO2 but also massive release of seabed methane was the driver for CIE and PETM."],["dc.identifier.doi","10.1073/pnas.1518116113"],["dc.identifier.isi","000379694100033"],["dc.identifier.pmid","27354522"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/40090"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0027-8424"],["dc.title","Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","e49531"],["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","PLOS ONE"],["dc.bibliographiccitation.volume","7"],["dc.contributor.author","Gehler, Alexander"],["dc.contributor.author","Tütken, Thomas"],["dc.contributor.author","Pack, Andreas"],["dc.contributor.editor","Farke, Andrew A."],["dc.date.accessioned","2018-06-28T08:58:27Z"],["dc.date.available","2018-06-28T08:58:27Z"],["dc.date.issued","2012"],["dc.description.abstract","The oxygen (δ(18)O) and carbon (δ(13)C) isotope compositions of bioapatite from skeletal remains of fossil mammals are well-established proxies for the reconstruction of palaeoenvironmental and palaeoclimatic conditions. Stable isotope studies of modern analogues are an important prerequisite for such reconstructions from fossil mammal remains. While numerous studies have investigated modern large- and medium-sized mammals, comparable studies are rare for small mammals. Due to their high abundance in terrestrial ecosystems, short life spans and small habitat size, small mammals are good recorders of local environments."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2012"],["dc.identifier.doi","10.1371/journal.pone.0049531"],["dc.identifier.pmid","23226212"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/8329"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15153"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","final"],["dc.relation.eissn","1932-6203"],["dc.relation.orgunit","Fakultät für Geowissenschaften und Geographie"],["dc.rights","CC BY 2.5"],["dc.rights.uri","http://creativecommons.org/licenses/by/2.5/"],["dc.title","Oxygen and carbon isotope variations in a modern rodent community - implications for palaeoenvironmental reconstructions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","84"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Palaeogeography Palaeoclimatology Palaeoecology"],["dc.bibliographiccitation.lastpage","91"],["dc.bibliographiccitation.volume","310"],["dc.contributor.author","Gehler, Alexander"],["dc.contributor.author","Tuetken, Thomas"],["dc.contributor.author","Pack, Andreas"],["dc.date.accessioned","2018-11-07T08:51:42Z"],["dc.date.available","2018-11-07T08:51:42Z"],["dc.date.issued","2011"],["dc.description.abstract","The detection of diagenetic alteration is critical for palaeoclimate reconstruction that is based on the oxygen isotope composition of fossil bones and teeth. So far, no direct chemical proxy has been found to track diagenetic modification of the oxygen isotope ratios. Here, a new approach to identify diagenetic changes of delta O-18(PO4) values in skeletal apatite of small mammals by means of triple oxygen isotope analysis (O-16, O-17 and O-18) is presented. Our method is based on the fact that inhaled air oxygen (O-2) has an isotope anomaly on its rare isotope O-17. Inhaled air O-2 is a major source of oxygen in small land-living mammals. A fraction of the anomaly is transferred via body water to skeletal apatite, where it can be detected by means of delta O-17 and delta O-18 analyses. The approach, considering the current analytical uncertainty, is restricted to small mammals with body masses <= 1 kg. This is due to the low specific metabolic rates of large mammals, resulting in a lower fraction of oxygen inhaled via breathing relative to oxygen from other sources in their body water. Remnant negative O-17 anomalies derived from in vivo inhaled O-2 have been detected in enamel bioapatite of Eocene to Miocene rodent teeth while dentine of the same teeth lacks significant O-17 anomalies. This suggests preservation of the original phosphate oxygen isotope composition in enamel of these small mammal teeth. In contrast, O-17 anomalies in dentine have been erased due to diagenetic alteration with isotopically normal diagenetic fluids. Triple oxygen isotope analysis of bioapatite thus seems to be a useful new proxy to directly detect diagenetic alterations of the delta O-18(PO4) values of small mammal teeth. (C) 2011 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.palaeo.2011.04.014"],["dc.identifier.isi","000295608400010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/22001"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","0031-0182"],["dc.title","Triple oxygen isotope analysis of bioapatite as tracer for diagenetic alteration of bones and teeth"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]