Leaf waxes as recorders of paleoclimatic changes during the Paleocene–Eocene Thermal Maximum: Regional expressions from the Belluno Basin

Krishnan, Srinath; Pagani, Mark; Agnini, Claudia

doi:10.1016/j.orggeochem.2014.12.005

Cited by 14 publications

(13 citation statements)

References 104 publications

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“…The CMU, which marks the "core" of the PETM and ca. 80-100 kyr, showing a higher sedimentation rate than much of the remaining record (Dallanave et al, 2009;Krishnan et al, 2015).…”

Section: Integrated Stratigraphy and A Carbon Isotope Templatementioning

confidence: 88%

“…15 m Myr −1 . Although the deposition of hemipelagic sediment might suggest relatively constant SRs over time, the PETM and possibly other hyperthermal events in the Belluno Basin were characterized by higher SRs (Giusberti et al, 2007;Agnini et al, 2009;Tipple et al, 2011;Krishnan et al, 2015). The Scaglia Rossa at Cicogna appears to record fairly continuous sediment accumulation at moderately high deposition rates.…”

Section: The Cicogna Sectionmentioning

confidence: 95%

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Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)

Agnini

Spofforth²,

Dickens

et al. 2016

Clim. Past

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Abstract. We present records of stable carbon and oxygen isotopes, CaCO 3 content, and changes in calcareous nannofossil assemblages across an 81 m thick section of upper Paleocene-lower Eocene marine sedimentary rocks now exposed along the Cicogna Stream in northeast Italy. The studied stratigraphic section represents sediment accumulation in a bathyal hemipelagic setting from approximately 57.5 to 52.2 Ma, a multi-million-year time interval characterized by perturbations in the global carbon cycle and changes in calcareous nannofossil assemblages. The bulk carbonate δ 13 C profile for the Cicogna section, once placed on a common timescale, resembles that at several other locations across the world, and includes both a long-term drop in δ 13 C and multiple short-term carbon isotope excursions (CIEs). This precise correlation of widely separated δ 13 C records in marine sequences results from temporal changes in the carbon composition of the exogenic carbon cycle. However, diagenesis has likely modified the δ 13 C record at Cicogna, an interpretation supported by variations in bulk carbonate δ 18 O, which do not conform to expectations for a primary signal. The record of CaCO 3 content reflects a combination of carbonate dilution and dissolution, as also inferred at other sites. Our detailed documentation and statistical analysis of calcareous nannofossil assemblages show major differences before, during and after the Paleocene-Eocene Thermal Maximum. Other CIEs in our lower Paleogene section do not exhibit such a distinctive change; instead, these events are sometimes characterized by variations restricted to a limited number of taxa and transient shifts in the relative abundance of primary assemblage components. Both long-lasting and short-lived modifications to calcareous nannofossil assemblages preferentially affected nannoliths or holococcoliths such as Discoaster, Fasciculithus, Rhomboaster/Tribrachiatus, Sphenolithus and Zygrhablithus, which underwent distinct variations in abundance as well as permanent evolutionary changes in terms of appearances and disappearances. By contrast, placoliths such as Coccolithus and Toweius, which represent the main component of the assemblages, were characterized by a gradual decline in abundance over time. Comparisons of detailed nannofossil assemblage records at the Cicogna section and at ODP Site 1262 support the idea that variations in the relative and absolute abundances, even some minor changes, were globally synchronous. An obvious link is through climate forcing and carbon cycling, although the linkages between variations in calcareous nannoplankton, changes in δ 13 C records and oceanography will need additional work.

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“…The CMU, which marks the "core" of the PETM and ca. 80-100 kyr, showing a higher sedimentation rate than much of the remaining record (Dallanave et al, 2009;Krishnan et al, 2015).…”

Section: Integrated Stratigraphy and A Carbon Isotope Templatementioning

confidence: 88%

Section: The Cicogna Sectionmentioning

confidence: 95%

Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)

Agnini

Spofforth²,

Dickens

et al. 2016

Clim. Past

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“…Despite hundreds of papers published about the PETM since its discovery in the early 1990s (McInerney & Wing, ), there exist only 13 published PETM n ‐alkane records globally. Since 2011, when a global compilation of plant lipid records (from mostly terrestrial and open marine depositional environments) revealed an average CIE magnitude of –5.1‰ [McInerney and Wing], additional lipid δ 13 C records have added to the complexity of the global picture (Garel et al, ; Handley et al, ; Krishnan et al, ; Schoon et al, ; Sluijs et al, ; Tipple et al, ). The completeness and sampling resolution among these records varies tremendously.…”

Section: Discussionmentioning

confidence: 99%

“…In modern settings, the 14 C dating of fluvial and aeolian transported n ‐alkanes has shown that organic carbon from multiple sources is delivered contemporaneously to aquatic sediments, particularly near continents (Eglinton et al, ; French et al, ; Pearson & Eglinton, ; Pearson et al, ). Depending on the extent and rate of weathering and redeposition of older n ‐alkanes in the near‐shore environments, the relative proportion of fossil n ‐alkanes could differ among locations and is one possible explanation for the variability in the nearshore PETM records from France, Italy, Venezuela, and New Zealand (Garel et al, ; Handley et al, ; Jaramillo et al, ; Kaiho et al, ; Krishnan et al, ; Tipple et al, ). In contrast, the open marine records (Handley et al, ; Hasegawa et al, ; Pagani et al, ) may better preserve the full expression of CIE because they are comprised of aeolian transported n ‐alkanes almost exclusively derived from contemporaneous terrestrial vegetation (i.e., little to no contribution from reworked fossil material; Kawamura et al, ; Schefuß et al, ).…”

Section: Discussionmentioning

confidence: 99%

Carbon Isotope Record of Trace n‐alkanes in a Continental PETM Section Recovered by the Bighorn Basin Coring Project (BBCP)

Baczynski

McInerney

Freeman

et al. 2019

Paleoceanog and Paleoclimatol

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Continental sedimentary records of early Paleogene hyperthermals are typically limited to weathered, often discontinuous, outcrop exposures. In 2011, the Bighorn Basin Coring Project (BBCP) collected the first continuous terrestrial records of the Paleocene‐Eocene Thermal Maximum (PETM) in the Bighorn Basin, Wyoming. Organic matter preservation was poor during the PETM, even in core material. Concentrations of leaf waxes during the PETM are too low for compound‐specific carbon isotope analysis by conventional means. However, the recent development of picomolar‐scale compound‐specific isotope analyses (pico‐CSIA) has reduced sample requirements and enabled measurements of carbon isotope ratios of n‐alkanes across the PETM in the Basin Substation core. While the prominent, negative carbon isotope excursion in total organic carbon that typically identifies the PETM in the sedimentary record is absent from the core, lithostratigraphic, biostratigraphic, and chemostratigraphic data suggest that the most likely position of the PETM is from ~87.82‐ to ~50‐m composite depth. This ~40‐m interval coincides with the lowest weight percent organic carbon, n‐alkane abundances, and n‐alkane δ13C values and the highest n‐alkane average chain lengths. Comparison of the n‐alkane isotope record from the core with that from organic‐rich rocks exposed in the SE Bighorn Basin suggests that n‐alkanes in the core fail to express the full magnitude of the carbon isotope excursion. We hypothesize that floodplain sediments at Basin Substation contain a mixture of PETM and reworked fossil n‐alkanes. Low total organic carbon suggests that PETM climate accelerated organic matter decay rates and floodplains may have acted as a carbon source during the PETM.

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“…Recently, a number of high‐resolution terrestrial organic n alkane records across hyperthermal events during the early Eocene (PETM and Eocene Thermal Maximum 2) have indicated pronounced decreases in δ D during peak warming [ Pagani et al, ; Smith et al, ; Tipple et al, ; Krishnan et al, 2014 , 2015]. These hyperthermal events involved large pulses of carbon to the atmosphere‐ocean reservoir and global warming on the order of 5–8 K over a geologically short timescale (10 3 –10 4 years) [ Zachos et al, ].…”

Section: Discussionmentioning

confidence: 99%

A mechanistic analysis of early Eocene latitudinal gradients of isotopes in precipitation

Winnick

Caves

Chamberlain

2015

Geophysical Research Letters

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We use a one‐dimensional reactive transport model of isotopes in precipitation (δ18O) to investigate the physical mechanisms controlling global meridional isotope profiles under early Eocene hothouse conditions. Simulations of early Eocene precipitation isotopes display reduced meridional gradients relative to the modern climate with the largest increases in δ18O occurring at high latitudes, matching proxy data. These reduced gradients are controlled primarily by polar amplification that increases high‐latitude length scales of specific humidity and match our compilation of proxy‐based reconstructions. Comparing Eocene general circulation model simulations run with pCO2 of 2240 and 4480 ppm, we find that meridional isotopic profiles are insensitive to the associated 5°C change in global temperatures due to the relative lack of polar amplification. Finally, we hypothesize that observed negative δD anomalies in precipitation during peak warming of early Eocene hyperthermal events are the result of a theorized reduction in the strength of midlatitude transient eddies.

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Leaf waxes as recorders of paleoclimatic changes during the Paleocene–Eocene Thermal Maximum: Regional expressions from the Belluno Basin

Cited by 14 publications

References 104 publications

Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)

Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)

Carbon Isotope Record of Trace n‐alkanes in a Continental PETM Section Recovered by the Bighorn Basin Coring Project (BBCP)

A mechanistic analysis of early Eocene latitudinal gradients of isotopes in precipitation

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