Size‐fraction‐specific isotope variations as a framework to interpret early Eocene bulk sediment carbon isotope records

ABSTRACT This study focuses on marine sediments of the late Paleocene-early Eocene (∼55.5–49 Ma) interval from the Jaisalmer Basin of western India. It demarcates the Paleocene Eocene Thermal Maximum (PETM) using foraminiferal biostratigraphy and carbon isotope stratigraphy. A negative carbon isotope excursion of 4.5‰ delineates the PETM within the basin. We demarcate five foraminiferal biofacies using the detrended correspondence analysis. These reflect characteristics of ecology, bathymetry, relative age, and environment of deposition of the foraminifera. They record the response of foraminifera to the warmth of the PETM. Biofacies A was deposited within an inner neritic setting ∼55.5 Ma and includes benthic foraminifera Haplophragmoides spp., Ammobaculites spp., and Lenticulina spp. The presence of Pulsiphonina prima and Valvulineria scorbiculata in Biofacies B suggests an increase in runoff conditions in the basin. Fluctuating trophic conditions prevailed between ∼54–50 Ma. It is evidenced by alternating Biofacies C (endobenthic and chiloguembelinids of eutrophic conditions) and Biofacies D (epibenthic and acarininids of oligotrophic conditions). Biofacies E is dominated by deep-dwelling parasubbotinids, indicating an increase in bathymetry, possibly corresponding to the Early Eocene Climatic Optimum (∼49 Ma).

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Technical note: Accelerate coccolith size separation via repeated centrifugation

10.5194/bg-2020-341 ◽

2020 ◽

Author(s):

Hongrui Zhang ◽

Chuanlian Liu ◽

Luz Maria Mejia ◽

Heather Stoll

Keyword(s):

Stable Isotopes ◽

Angular Velocity ◽

Carbon Cycle ◽

Marine Sediment ◽

Size Fraction ◽

Technical Note ◽

Bulk Sediment ◽

Matlab Code ◽

Clumped Isotope ◽

Carbon Analysis

Abstract. Coccolithophore play a key role in the marine carbon cycle and ecosystem. The carbonate shells produced by coccolithophore, named as coccolith, could be well preserved in the marine sediment for million years and become an excellent archive for paleoclimate studies. The micro filtering and sinking-decanting method have been successfully designed for coccolith separation and promoted the development of geochemistry studies on coccolith, such as the stable isotopes and Sr / Ca ratio. However, these two methods are still not efficient enough for the sample-consuming methods. In this study, the trajectory of coccoliths movement during a centrifugation process was calculated in theory and carefully tested by separations in practice. We offer a matlab code to estimate the appropriate parameter, angular velocity at a fixed centrifugation duration, for separating certain coccolith size fractions from bulk sediment. This work could improve the efficiency of coccolith separation, especially for the finest size fraction and make it possible to carry the clumped isotope and radio carbon analysis on coccolith in sediment.

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Astronomically tuned age model for the early Eocene carbon isotope events: A new high-resolution δ13 Cbenthic record of ODP Site 1263 between ~ 49 and ~ 54 Ma

Newsletters on Stratigraphy ◽

10.1127/nos/2016/0077 ◽

2016 ◽

Vol 49 (2) ◽

pp. 383-400 ◽

Cited By ~ 36

Author(s):

V. Lauretano ◽

F.J. Hilgen ◽

J.C. Zachos ◽

L.J. Lourens

Keyword(s):

High Resolution ◽

Carbon Isotope ◽

Early Eocene ◽

Age Model

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Discussion on the Late Palaeocene–Early Eocene and Toarcian (Early Jurassic) carbon isotope excursions: a comparison of their time scales, associated environmental change, causes and consequencesJournal, Vol. 164, 2007, 1093–1108

Journal of the Geological Society ◽

10.1144/0016-76492007-157 ◽

2008 ◽

Vol 165 (4) ◽

pp. 875-880 ◽

Cited By ~ 5

Author(s):

J.M. McArthur ◽

A.S. Cohen ◽

A.L. Coe ◽

D.B. Kemp ◽

R.J. Bailey ◽

...

Keyword(s):

Environmental Change ◽

Carbon Isotope ◽

Time Scales ◽

Early Jurassic ◽

Early Eocene

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Geochemical indications for the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals in terrestrial sediments of the Canadian Arctic

Geosphere ◽

10.1130/ges02398.1 ◽

2022 ◽

Author(s):

Lutz Reinhardt ◽

Werner von Gosen ◽

Andreas Lückge ◽

Martin Blumenberg ◽

Jennifer M. Galloway ◽

...

Keyword(s):

Carbon Isotope ◽

Early Eocene ◽

Isotope Data ◽

Complete Section ◽

Thermal Maximum ◽

Terrestrial Sediments ◽

Deformation Features ◽

Isotope Record ◽

Hydrological System ◽

Hyperthermal Events

During the late Paleocene to early Eocene, clastic fluvial sediments and coals were deposited in northern high latitudes as part of the Margaret Formation at Stenkul Fiord (Ellesmere Island, Nunavut, Canada). Syn-sedimentary tectonic movements of the Eurekan deformation continuously affected these terrestrial sediments. Different volcanic ash layers occur, and unconformities subdivide the deposits into four sedimentary units. Rare vertebrate fossils indicate an early Eocene (Graybullian) age for the upper part of the Stenkul Fiord outcrop. Here, we present carbon isotope data of bulk coal, related organic-rich mud and siltstones, a plant leaf wax-derived alkane, and additional plant remains. These data provide a complete carbon isotope record of one stratigraphic section with defined unconformity positions and in relation to other Eurekan deformation features. A previously dated ash layer MA-1 provided a U-Pb zircon age of 53.7 Ma and is used as a stratigraphic tie point, together with a discrete negative carbon isotope excursion found above MA-1 in a closely sampled coal seam. The excursion is identified as the likely expression of the I-1 hyperthermal event. Based on our isotope data that reflect the early Eocene dynamics of the carbon cycle, this tie point, and previous paleontological constraints from vertebrate fossils, the locations of the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals and their extent along the complete section are herein identified. Within the intervals of the PETM and ETM-2 hyperthermal events, increasing amounts of clastic sediments reached the site toward the respective end of the event. This is interpreted as a response of the fluvial depositional system to an intensified hydrological system during the hyperthermal events. Our study establishes an enhanced stratigraphic framework allowing for the calculation of average sedimentation rates of different intervals and considerations on the completeness of the stratigraphic record. As one of the few high-latitude outcrops of early Eocene terrestrial sediments, the Stenkul Fiord location offers further possibilities to study the effects of extreme warming events in the Paleogene.

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Paleoenvironmental response of midlatitudinal wetlands to Paleocene–early Eocene climate change (Schöningen lignite deposits, Germany)

Climate of the Past ◽

10.5194/cp-15-1741-2019 ◽

2019 ◽

Vol 15 (5) ◽

pp. 1741-1755 ◽

Cited By ~ 2

Author(s):

Katharina Methner ◽

Olaf Lenz ◽

Walter Riegel ◽

Volker Wilde ◽

Andreas Mulch

Keyword(s):

Carbon Isotope ◽

North Sea ◽

Terrestrial Ecosystems ◽

High Pco2 ◽

Organic Carbon Content ◽

Early Eocene ◽

Thermal Maximum ◽

Early Paleogene ◽

Sea Coast ◽

North Sea Coast

Abstract. The early Paleogene is marked by multiple negative carbon isotope excursions (CIEs) that reflect massive short-term carbon cycle perturbations that coincide with significant warming during a high-pCO2 world, affecting both marine and terrestrial ecosystems. Records of such hyperthermals from the marine–terrestrial interface (e.g., estuarine swamps and mire deposits) are therefore of great interest as their present-day counterparts are highly vulnerable to future climate and sea level change. Here, we assess paleoenvironmental changes of midlatitudinal late Paleocene–early Eocene peat mire records along the paleo-North Sea coast. We provide carbon isotope data of bulk organic matter (δ13CTOC), organic carbon content (%TOC), and palynological data from an extensive peat mire deposited at a midlatitudinal (ca. 41∘ N) coastal site (Schöningen, Germany). The δ13CTOC data show a carbon isotope excursion of −1.3 ‰ (mean decrease in δ13CTOC; −1.7 ‰ at the onset of CIE) coeval with a conspicuous Apectodinium acme. Due to the exceptionally large stratigraphic thickness of the CIE at Schöningen (10 m of section) we established a detailed palynological record that indicates only minor changes in paleovegetation leading into and during this event. Instead, paleovegetation changes mostly follow natural successions in response to changes along the marine–terrestrial interface. The available age constraints for the Schöningen Formation hamper a solid assignment of the detected CIE to a particular hyperthermal such as the Paleocene–Eocene Thermal Maximum (PETM) or any succeeding hyperthermal event such as the Eocene Thermal Maximum 2 (ETM2). Compared to other nearby peat mire records (Cobham, UK; Vasterival, F) it appears that wetland deposits around the Paleogene North Sea have a consistent CIE magnitude of ca. −1.3 ‰ in δ13CTOC. Moreover, the Schöningen record shares major characteristics with the Cobham Lignite PETM record, including evidence for increased fire activity prior to the CIE, minor plant species change during the hyperthermal, a reduced CIE in δ13CTOC, and drowning of the mire (marine ingressions) during much of the Schöningen CIE event. This suggests that either the Schöningen CIE reflects the PETM or that early Paleogene hyperthermals similarly affected paleoenvironmental conditions of a major segment of the paleo-North Sea coast.

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