scholarly journals Maastrichtian–Rupelian paleoclimates in the southwest Pacific – a critical re-evaluation of biomarker paleothermometry and dinoflagellate cyst paleoecology at Ocean Drilling Program Site 1172

2021 ◽  
Vol 17 (6) ◽  
pp. 2393-2425
Author(s):  
Peter K. Bijl ◽  
Joost Frieling ◽  
Margot J. Cramwinckel ◽  
Christine Boschman ◽  
Appy Sluijs ◽  
...  

Abstract. Sea surface temperature (SST) reconstructions based on isoprenoid glycerol dialkyl glycerol tetraether (isoGDGT) distributions from the Eocene southwest (SW) Pacific Ocean are unequivocally warmer than can be reconciled with state-of-the-art fully coupled climate models. However, the SST signal preserved in sedimentary archives can be affected by contributions of additional isoGDGT sources. Methods now exist to identify and possibly correct for overprinting effects on the isoGDGT distribution in marine sediments. Here, we use the current proxy insights to (re-)assess the reliability of the isoGDGT-based SST signal in 69 newly analyzed and 242 reanalyzed sediments at Ocean Drilling Program (ODP) Site 1172 (East Tasman Plateau, Australia) following state-of-the-art chromatographic techniques. We compare our results with paleoenvironmental and paleoclimatologic reconstructions based on dinoflagellate cysts. The resulting ∼ 130 kyr resolution Maastrichtian–Oligocene SST record based on the TetraEther indeX of tetraethers with 86 carbon atoms (TEX86) confirms previous conclusions of anomalous warmth in the early Eocene SW Pacific and remarkably cool conditions during the mid-Paleocene. Dinocyst diversity and assemblages show a strong response to the local SST evolution, supporting the robustness of the TEX86 record. Soil-derived branched GDGTs stored in the same sediments are used to reconstruct mean annual air temperature (MAAT) of the nearby land using the Methylation index of Branched Tetraethers with 5-methyl bonds (MBT'5me) proxy. MAAT is consistently lower than SST during the early Eocene, independent of the calibration chosen. General trends in SST and MAAT are similar, except for (1) an enigmatic absence of MAAT rise during the Paleocene–Eocene Thermal Maximum and Middle Eocene Climatic Optimum, and (2) a subdued middle–late Eocene MAAT cooling relative to SST. Both dinocysts and GDGT signals suggest a mid-shelf depositional environment with strong river runoff during the Paleocene–early Eocene progressively becoming more marine thereafter. This trend reflects gradual subsidence and more pronounced wet/dry seasons in the northward-drifting Australian hinterland, which may also explain the subdued middle Eocene MAAT cooling relative to that of SST. The overall correlation between dinocyst assemblages, marine biodiversity and SST changes suggests that temperature exerted a strong influence on the surface-water ecosystem. Finally, we find support for a potential temperature control on compositional changes of branched glycerol monoalkyl glycerol tetraethers (brGMGTs) in marine sediments. It is encouraging that a critical evaluation of the GDGT signals confirms that most of the generated data are reliable. However, this also implies that the high TEX86-based SSTs for the Eocene SW Pacific and the systematic offset between absolute TEX86-based SST and MBT'5me-based MAAT estimates remain without definitive explanation.

2021 ◽  
Author(s):  
Peter K. Bijl ◽  
Joost Frieling ◽  
Margot J. Cramwinckel ◽  
Christine Boschman ◽  
Appy Sluijs ◽  
...  

Abstract. Sea surface temperature (SST) reconstructions based on isoprenoid glycerol dialkyl glycerol tetraether (isoGDGT) distributions from the Eocene southwest (sw) Pacific Ocean are unequivocally warmer than can be reconciled with state-of-the-art fully coupled climate models. However, the SST signal preserved in sedimentary archives can be affected by contributions of additional isoGDGT sources. Methods now exist to identify and possibly correct for overprinting effects on the isoGDGT distribution in marine sediments. We here use the current proxy insights to assess the reliability of the isoGDGT-based SST signal in 69 newly analysed and 242 re-analysed sediments ODP Site 1172 (East Tasman Plateau, Australia) following state-of-the-art chromatographic techniques, in context of paleo-environmental and paleoclimatologic reconstructions based on dinoflagellate cysts. The resulting ~130 kyr-resolution Maastrichtian-Oligocene TEX86-based SST record confirms previous conclusions of anomalous warmth in the early Eocene sw Pacific and remarkably cool conditions during the mid-Paleocene. Dinocyst diversity and assemblages show a strong response to the local SST evolution, supporting the robustness of the TEX86 record. Soil-derived branched GDGTs stored in the same sediments are used to reconstruct mean annual air temperature (MAAT) of the nearby land using the MBT'5me proxy. MAAT is consistently lower than SST during the early Eocene, independent of the calibration chosen. General trends in SST and MAAT are similar, except for: 1) an enigmatic absence of MAAT rise during the Paleocene-Eocene Thermal Maximum and Middle Eocene Climatic Optimum, and 2) a subdued middle–late Eocene MAAT cooling relative to SST. Both dinocysts and GDGT signals suggest a mid-shelf depositional environment with strong river-runoff during the Paleocene-early Eocene, progressively becoming more marine thereafter. This trend reflects gradual drying and more pronounced wet/dry seasons in the northward drifting Australian hinterland, which may also explain the subdued middle Eocene MAAT cooling relative to that of SST. The overall correlation between dinocyst assemblages, marine biodiversity and SST changes suggests that temperature exerted a strong influence on the surface-water ecosystem, probably in part through sea level changes caused by steric effects. Finally, we find support for a potential temperature control on compositional changes of branched glycerol monoalkyl glycerol tetraethers (brGMGTs) in marine sediments. It is encouraging that a critical evaluation of the GDGT signals confirms the vast majority of the generated data is reliable. However, this also implies the high TEX86-based SSTs for the Eocene sw Pacific, and the systematic offset between absolute TEX86-based SST and MBT'5me-based MAAT estimates remain unexplained.


2021 ◽  
Author(s):  
Peter Bijl ◽  
Joost Frieling ◽  
Margot J. Cramwinckel ◽  
Christine Boschman ◽  
Appy Sluijs ◽  
...  

<p>Sea surface temperature (SST) reconstructions based on isoprenoid glycerol dialkyl glycerol tetraether (isoGDGT) distributions from the Eocene southwest (sw) Pacific Ocean are unequivocally warmer than can be reconciled with state-of-the-art fully coupled climate models. However, the SST signal preserved in sedimentary archives can be obscured by contributions of additional isoGDGT sources. We here use current proxy insights to assess the reliability of the isoGDGT-based SST signal in 69 newly analysed and 242 re-analysed samples covering the Maastrichtian to Oligocene from ODP Site 1172 (East Tasman Plateau, Australia) following state-of-the-art chromatographic techniques. We then reinterpret the record in context of paleo-environmental and paleoclimatologic reconstructions based on dinoflagellate cysts. Our ~130 kyr-resolution SST record reaffirms previous reconstructions of anomalous warmth in the early Eocene sw Pacific and remarkably cool conditions during the mid-Paleocene. Dinocyst diversity and temperature-sensitive taxa show a strong response to the local SST evolution, supporting the robustness of the marine biomarker record.  In addition, the long-term isoGDGT and dinocyst records provide further support for an apparent temperature control on compositional changes of branched glycerol monoalkyl glycerol tetraethers (brGMGTs), recorded in the same samples.</p><p>Soil-derived branched GDGTs (brGDGTs) stored in the same sediments are used to reconstruct mean annual air temperature (MAAT) of the nearby land through the MBT’<sub>5me</sub> proxy. General trends in SST and MAAT are similar, except for 1) an enigmatic absence of MAAT rise during the Paleocene-Eocene Thermal Maximum and Middle Eocene Climatic Optimum, and 2) a subdued middle–late Eocene MAAT cooling relative to SST. Both dinocyst assemblages and brGDGT indices (the isomerization index) suggest a mid-shelf depositional environment with strong river-runoff during the Paleocene-early Eocene, becoming more open marine thereafter. This trend reflects gradual drying and more seasonal precipitation regime in the northward drifting Australian hinterland. The overall correlation between dinocyst assemblages, biodiversity and SST changes suggests that temperature and associated environmental changes exert a strong influence on the surface-water ecosystem.</p>


Author(s):  
Paul F. Green ◽  
Peter Japsen

Apatite fission-track analysis (AFTA) data in two Upper Jurassic core samples from the 231 m deep Blokelv-1 borehole, Jameson Land, East Greenland, combined with vitrinite reflectance data and regional AFTA data, define three palaeo-thermal episodes. We interpret localised early Eocene (55– 50 Ma) palaeotemperatures as representing localised early Eocene heating related to intrusive activity whereas we interpret late Eocene (40–35 Ma) and late Miocene (c. 10 Ma) palaeotemperatures as representing deeper burial followed by successive episodes of exhumation. For a palaeogeothermal gradient of 30°C/km and likely palaeo-surface temperatures, the late Eocene palaeotemperatures require that the Upper Jurassic marine section in the borehole was buried below a 2750 m thick cover of Upper Jurassic – Eocene rocks prior to the onset of late Eocene exhumation. As these sediments are now near outcrop at c. 200 m above sea level, they have been uplifted by at least 3 km since maximum burial during post-rift thermal subsidence. The results are consistent with estimates of rock uplift on Milne Land since the late Eocene and with interpretation of Ocean Drilling Program (ODP) data off South-East Greenland suggesting that mid-Cenozoic uplift of the margin triggered the marked influx of coarse clastic turbidites during the late Oligocene above a middle Eocene to upper Oligocene hiatus.


2011 ◽  
Vol 12 ◽  
pp. 15-23 ◽  
Author(s):  
C. Escutia ◽  
H. Brinkhuis ◽  
A. Klaus ◽  

Integrated Ocean Drilling Program (IODP) Expedition 318, Wilkes Land Glacial History, drilled a transect of sites across the Wilkes Land margin of Antarctica to provide a long-term record of the sedimentary archives of Cenozoic Antarctic glaciation and its intimate relationships with global climatic and oceanographic change. The Wilkes Land drilling program was undertaken to constrain the age, nature, and paleoenvironment of the previously only seismically inferred glacial sequences. The expedition (January–March 2010) recovered ~2000 meters of high-quality middle Eocene–Holocene sediments from water depths between 400 m and 4000 m at four sites on the Wilkes Land rise (U1355, U1356, U1359, and U1361) and three sites on the Wilkes Land shelf (U1357, U1358, and U1360). <br><br> These records span ~53 million years of Antarctic history, and the various seismic units (WL-S4–WL-S9) have been successfully dated. The cores reveal the history of the Wilkes Land Antarctic margin from an ice-free “greenhouse” Antarctica, to the first cooling, to the onset and erosional consequences of the first glaciation and the subsequent dynamics of the waxing and waning ice sheets, all the way to thick, unprecedented "tree ring style" records with seasonal resolution of the last deglaciation that began ~10,000 y ago. The cores also reveal details of the tectonic history of the Australo-Antarctic Gulf from 53 Ma, portraying the onset of the second phase of rifting between Australia and Antarctica, to ever-subsiding margins and deepening, to the present continental and ever-widening ocean/continent configuration. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.12.02.2011" target="_blank">10.2204/iodp.sd.12.02.2011</a>


Polar Record ◽  
1989 ◽  
Vol 25 (153) ◽  
pp. 99-106 ◽  
Author(s):  
Michael J. Hambrey ◽  
Birger Larsen ◽  
Werner U. Ehrmann

AbstractDuring Leg 119 of the Ocean Drilling Program, between December 1987 and February 1988, six holes were drilled in the Kerguelen Plateau, southern Indian Ocean, and five in Prydz Bay at the mouth of the Amery Ice Shelf, on the East Antarctic continental shelf. The Prydz Bay holes, reported here, form a transect from the inner shelf to the continental slope, recording a prograding sequence of possible Late Paleozoic to Eocene continental sediments of fluvial aspect, followed by several hundred metres of Early Oligocene (possibly Middle Eocene) to Quaternary glaciallydominated sediments. This extends the known onset of large-scale glaciation of Antarctica back to about 36–40 million years ago, the sedimentary record suggesting that a fully developed East Antarctic Ice Sheet reached the coast at Prydz Bay at this time, and was more extensive than the present sheet. Subsequent glacial history is complex, with the bulk of sedimentation in the outer shelf taking place close to the grounding line of an extended Amery Ice S helf. However, breaks in the record and intervals of no recovery may hide evidence of periods of glacial retreat.


2004 ◽  
Vol 213 ◽  
pp. 325-336 ◽  
Author(s):  
Rosalba Bonaccorsi

Although on Mars no near-surface life has been detected, some preservation of organics with depth is expected. Stratigraphic and geochemical information on low-organic carbon (50% samples with Total Organic Carbon = 0.05 − 0.12%) Fe-oxides/oxyhydroxide-rich horizons of deeply buried red paleosoils (late Paleocene-early Eocene(?) in age) are presented here. They were retrieved during the Ocean Drilling Program (ODP) Leg 197 (Emperor Seamounts, North Pacific Transect). Organic traces in Hole 1205A are likely to reflect a complex history of paleosoil formation. Materials from an extremely deep (sub-basement) diagenetic setting, i.e., 46.8 to 309.9 meters below seafloor (mbsf), could represent a model for possible deep subsurface soils preserved on Mars.


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