A multi-proxy reconstruction of Late Cretaceous climate
<p>The Late Cretaceous (100.5–66.0 Ma) was a greenhouse world with high atmospheric CO<sub>2</sub>, which fluctuated on long and short timescales, that can provide insights into how Earth’s climate system operates under different CO<sub>2</sub> levels to today. This the...
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| Format: | Thesis |
| Language: | English |
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2018
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| _version_ | 1797110646141091840 |
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| author | O'Connor, LK |
| author2 | Robinson, S |
| author_facet | Robinson, S O'Connor, LK |
| author_sort | O'Connor, LK |
| collection | OXFORD |
| description | <p>The Late Cretaceous (100.5–66.0 Ma) was a greenhouse world with high atmospheric CO<sub>2</sub>, which fluctuated on long and short timescales, that can provide insights into how Earth’s climate system operates under different CO<sub>2</sub> levels to today. This thesis applies a multi-proxy approach to reconstructing palaeoclimate through the collapse of the Late Cretaceous greenhouse, at tectonic to sub-orbital timescales, with the goal of disentangling CO<sub>2</sub> from other climatic drivers. This thesis demonstrates that, although atmospheric CO<sub>2</sub> was a dominant driver, local sea-surface temperature, sedimentation patterns, and water chemistry were influenced by changing circulation and orbital forcing on a range of timescales.</p>
<p>New multi-proxy sea-surface temperature data confirms previous studies by demonstrating anomalous warmth in the Late Cretaceous southern high latitudes but different proxies show different temporal trends, attributed to seasonal biases. Changing strength of seasonality may reflect the onset of deep-water formation in the South Atlantic during the Campanian, delivering warm, tropical waters to the south Atlantic.</p>
<p>A hierarchy of orbital cycles from precession to 2.4 Myr eccentricity has been identified in a Campanian hemipelagic sequence from the Mississippi Embayment, USA. The early Campanian record shows a strong influence of precession; however, in the late Campanian, the record is dominated by signals of obliquity. This change is attributed to a decreasing global temperature and CO<sub>2</sub>, affecting the sensitivity of the region to different orbital cycles.</p>
<p>The Plenus Cold Event was a brief period of cooling and re-oxygenation during Oceanic Anoxic Event 2 (Cenomanian–Turonian boundary time) attributed to high rates of organic-carbon burial and silicate weathering drawing down CO<sub>2</sub> and thus global temperatures. A global data compilation shows significant inconsistencies in the timing and sequence of climatic changes at different sites, suggesting a strong local overprint on temperature and redox changes in local water-masses.</p> |
| first_indexed | 2024-03-07T07:57:45Z |
| format | Thesis |
| id | oxford-uuid:98329d14-377b-4b7f-944e-654d933f96f8 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T07:57:45Z |
| publishDate | 2018 |
| record_format | dspace |
| spelling | oxford-uuid:98329d14-377b-4b7f-944e-654d933f96f82023-09-01T09:07:43ZA multi-proxy reconstruction of Late Cretaceous climateThesishttp://purl.org/coar/resource_type/c_db06uuid:98329d14-377b-4b7f-944e-654d933f96f8PaleoclimatologyEnglishHyrax Deposit2018O'Connor, LKRobinson, SJenkyns, H<p>The Late Cretaceous (100.5–66.0 Ma) was a greenhouse world with high atmospheric CO<sub>2</sub>, which fluctuated on long and short timescales, that can provide insights into how Earth’s climate system operates under different CO<sub>2</sub> levels to today. This thesis applies a multi-proxy approach to reconstructing palaeoclimate through the collapse of the Late Cretaceous greenhouse, at tectonic to sub-orbital timescales, with the goal of disentangling CO<sub>2</sub> from other climatic drivers. This thesis demonstrates that, although atmospheric CO<sub>2</sub> was a dominant driver, local sea-surface temperature, sedimentation patterns, and water chemistry were influenced by changing circulation and orbital forcing on a range of timescales.</p> <p>New multi-proxy sea-surface temperature data confirms previous studies by demonstrating anomalous warmth in the Late Cretaceous southern high latitudes but different proxies show different temporal trends, attributed to seasonal biases. Changing strength of seasonality may reflect the onset of deep-water formation in the South Atlantic during the Campanian, delivering warm, tropical waters to the south Atlantic.</p> <p>A hierarchy of orbital cycles from precession to 2.4 Myr eccentricity has been identified in a Campanian hemipelagic sequence from the Mississippi Embayment, USA. The early Campanian record shows a strong influence of precession; however, in the late Campanian, the record is dominated by signals of obliquity. This change is attributed to a decreasing global temperature and CO<sub>2</sub>, affecting the sensitivity of the region to different orbital cycles.</p> <p>The Plenus Cold Event was a brief period of cooling and re-oxygenation during Oceanic Anoxic Event 2 (Cenomanian–Turonian boundary time) attributed to high rates of organic-carbon burial and silicate weathering drawing down CO<sub>2</sub> and thus global temperatures. A global data compilation shows significant inconsistencies in the timing and sequence of climatic changes at different sites, suggesting a strong local overprint on temperature and redox changes in local water-masses.</p> |
| spellingShingle | Paleoclimatology O'Connor, LK A multi-proxy reconstruction of Late Cretaceous climate |
| title | A multi-proxy reconstruction of Late Cretaceous climate |
| title_full | A multi-proxy reconstruction of Late Cretaceous climate |
| title_fullStr | A multi-proxy reconstruction of Late Cretaceous climate |
| title_full_unstemmed | A multi-proxy reconstruction of Late Cretaceous climate |
| title_short | A multi-proxy reconstruction of Late Cretaceous climate |
| title_sort | multi proxy reconstruction of late cretaceous climate |
| topic | Paleoclimatology |
| work_keys_str_mv | AT oconnorlk amultiproxyreconstructionoflatecretaceousclimate AT oconnorlk multiproxyreconstructionoflatecretaceousclimate |