Quantitative Temperature Records of mid Cretaceous Hothouse PaleoClimate

Quantitative temperature records of mid Cretaceous hothouse: Evidence from halite fluid inclusions

Authors:

Zhang et al

Abstract:

Quantitative temperature reconstructions for the mid Cretaceous are still rare although its typical greenhouse climate is regarded as one of the best analogues for future global warming. For the first time, mid Cretaceous temperatures were quantitatively reconstructed based on homogenization temperatures (Th) of halite fluid inclusions from the Lower Member of the Nong Bok Formation in the Thakhek mining area, Laos. Petrological features and primary textures of halite indicate a shallow water setting during halite formation that allows the use of homogenization temperatures as air temperature proxy. Obtained homogenization temperatures mainly range from 30 to 50 °C, probably representing local air temperature conditions of Laos during the mid Cretaceous. The determined temperatures are relatively similar to temperatures in many modern and ancient evaporative settings. The maximum homogenization temperature (ThMax) for the Nong Bok Formation of 62.1 °C is significantly higher than existing mid Cretaceous paleotemperature records from both continental and marine sediments and comparable with the temperature records from the contemporaneous Mengyejing Formation of Yunnan, Southern China. The correspondence of the temperature records from Laos and Yunnan implies that very high temperature conditions prevailed in the region. Our results and other reconstructed very high temperatures from potash deposits (e.g., 59 °C for the Silurian Michigan Basin and 58 °C for the Quaternary Lop Nur region) suggest that extremely high temperatures probably had an important impact on the formation of the large potash deposits of the world. However, more studies are needed to improve our understanding of the detailed and quantitative relationships between temperature conditions and potash formation.

How Fast was the Onset of the Paleocene-Eocene Thermal Maximum? Was a Comet to Blame?!?!

A Comet Caused the PETM!

Evidence for a rapid release of carbon at the Paleocene-Eocene thermal maximum

Authors:

Wright et al

Abstract:

The Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE) are often touted as the best geologic analog for the current anthropogenic rise in pCO2. However, a causal mechanism for the PETM CIE remains unidentified because of large uncertainties in the duration of the CIE’s onset. Here, we report on a sequence of rhythmic sedimentary couplets comprising the Paleocene/Eocene Marlboro Clay (Salisbury Embayment). These couplets have corresponding δ18O cycles that imply a climatic origin. Seasonal insolation is the only regular climate cycle that can plausibly account for δ18O amplitudes and layer counts. High-resolution stable isotope records show 3.5‰ δ13C decrease over 13 couplets defining the CIE onset, which requires a large, instantaneous release of 13C-depleted carbon. During the CIE, a clear δ13C gradient developed on the shelf with the largest excursions in shallowest waters, indicating atmospheric δ13C decreased by ∼20‰. Our observations and revised release rate are consistent with an atmospheric perturbation of 3,000-gigatons of carbon (GtC).

No! It Did NOT!

Onset of carbon isotope excursion at the Paleocene-Eocene thermal maximum took millennia, not 13 years

Authors:

Zeebee et al

Abstract:

The Paleocene-Eocene thermal maximum (PETM) may represent the best paleo-analog for rapid and massive carbon release to the ocean and atmosphere. Thus, constraining the carbon release rate at its onset is critical. Wright and Schaller (1) use records from apparently rhythmically layered shelf sediments to argue that the layering is annual and that the onset of the carbon isotope excursion (CIE, fingerprint for carbon release) in the surface ocean was complete in 13 y. Using basic carbon cycle and climate considerations, we show this is not feasible. In fact, Wright and Schaller’s isotope records indicate that the CIE onset took at least several millennia. This finding rules out a cometary origin of the carbon release.

Yes, it did!

Reply to Pearson and Nicholas, Stassen et al., and Zeebe et al.: Teasing out the missing piece of the PETM puzzle

Authors:

Wright et al

Abstract:

Understanding the Paleocene-Eocene Thermal Maximum (PETM) critically depends on knowing the rate at which the perturbation carbon was released. In our report (1) we argue that the layered Marlboro Clay may provide this important constraint. Our strongest evidence in support of the rapid release of carbon at the onset of the PETM is the differential response of the %CaCO3 and δ13C in the Millville core. The sharp %CaCO3 decrease occurred over 4 mm, compared with the δ13C decrease over an interval of 25 cm (figure 3 in ref. 1). Temporal differences are predicted by a rapid (instantaneous) release of light carbon, which would lower the surface ocean Graphic in a matter of months, in contrast to the carbon isotopic equilibrium exchange, which occurs on the scale of a decade (2) and can only be recorded in a core with a high sedimentation rates (1). Based on the rhythmic bedding in the Marlboro Clay, we argue that the drop in %CaCO3 occurred in less than a year and the δ13C equilibrium was on the order of a decade.

My guess is probably not given all we know of the PETM.

The Late Paleozoic Transition From Ice House to Extreme Hot House Paleoclimate in Gondwana

A paleoclimatic review of southern South America during the late Paleozoic: A record from icehouse to extreme greenhouse conditions

Authors:

Limarino et al

Abstract:

This paper provides a review of the Late Mississippian to Permian paleoclimatic history for southern South America based on lithologic indicators, biostratigraphic information, and chronostratigraphic data. The region is divided into three major types of basins: 1. Eastern intraplate basins (e.g., Paraná Basin), 2. Western retroarc basins (e.g., Paganzo Basin) and 3. Western arc-related basins (e.g., Río Blanco Basin). Four major types of paleoclimatic stages are recognized in these basins: 1. glacial (late Visean–early Bashkirian), 2. terminal glacial (Bashkirian–earliest Cisuralian) 3. postglacial (Cisuralian–early Guadalupian), and 4. semiarid–arid (late Guadalupian–Lopingian). The glacial stage began in the late Visean and continued until the latest Serpukhovian or early Bashkirian in almost all of the basins in southern South America. During the Bashkirian–earliest Cisuralian (terminal glacial stage), glacial deposits disappeared almost completely in the western retroarc basins (e.g., Paganzo Basin) but glaciation persisted in the eastern basins (e.g., Paraná and Sauce Grande Basins). A gradual climatic amelioration (postglacial stage) began to occur during the earliest Permian when glacial deposits completely disappeared across all of South America. During this interval, glacial diamictites were replaced by thick coal beds in the Paraná Basin while north–south climatic belts began to be delineated in the western basins, which were likely controlled by the distribution of mountain belts along the Panthalassan Margin of South America. Towards the late Permian, climatic belts became less evident and semiarid or arid conditions dominated in the southern South America basins. Eolian dunes, playa lake deposits, and mixed eolian–fluvial sequences occur in the Paraná Basin and in the western retroarc basins. Volcanism and volcaniclastic sedimentation dominated along the western margin of South America at that time. The stratigraphic record obtained in southern South America supports a long duration transition from icehouse to extreme greenhouse conditions.