Opportunities and Challenges of a Highly Resolved Geological Timescale

2006 ◽  
Vol 12 ◽  
pp. 171-180
Author(s):  
Douglas H. Erwin
Keyword(s):  
High Resolution ◽  
Mass Extinction ◽  
Radiometric Dating ◽  
Early Paleozoic ◽  
Oceanic Anoxic Event ◽  
The Past ◽  
Anoxic Event ◽  
Cambrian Radiation ◽  
Correlation Techniques ◽  
Geological Timescale

The advent of greatly improved radiometric dating techniques with lower uncertainties, the development of new dating and correlation techniques, including vastly expanded quantitative biostratigraphic methods, and the possibility of reliable extension of orbital cyclostratigraphy into the Paleozoic all promise a great improvement in the ability of geologists to construct high-resolution temporal frameworks far deeper into the past. Such techniques have already allowed the generation of a high-resolution temporal framework for the Ediacaran-Cambrian radiation of metazoa, helped greatly narrow the duration of the great Permo-Triassic mass extinction and eliminated several hypothesized causes, and narrowed the duration of the oceanic anoxic event at the Cenomanian-Turonian (Late Cretaceous boundary). Temporal resolution of 100 kyr (0.02%) or even better into the early Paleozoic now seems likely, opening a host of new questions for reliable investigation. Further exploiting the possibilities of these techniques will require paleontologists to improve methods to integrate these disparate techniques, improve our understanding of the analysis of evolutionary rates, and confront the challenges of settings where geochronologic resolution may be greater than paleontologic resolution.

Onset of Oceanic Anoxic Event 2 in the Lower Saxony Basin – Insights fromhigh-resolution stable isotope stratigraphy and geochemical modelling

2021 ◽  
Author(s):  
Pia Müller ◽  
Ulrich Heimhofer ◽  
Christian Ostertag-Henning
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Stable Isotope ◽  
Carbon Cycle ◽  
Geochemical Modelling ◽  
Positive Anomaly ◽  
Lower Saxony ◽  
Data Set ◽  
Oceanic Anoxic Event ◽  
Anoxic Event

<p>The Oceanic Anoxic Event (OAE) 2 spanning the Cenomanian-Turonian boundary (93.5 Ma)<br>represents a major perturbation of the global carbon cycle and is marked by organic-rich<br>sediments deposited under oxygen-depleted conditions. In many studies the eruption of the<br>Caribbean LIP is considered to be the cause for rapidly increasing CO2 concentrations and<br>resulting global warming accompanied by widespread oceanic anoxia. In the Lower Saxony<br>Basin of northern Germany, the deposits of the OAE 2 are exposed in several industry drill<br>cores. In this study, the lower part of the OAE 2 has been studied in the HOLCIM 2011-3 drill<br>core. Sedimentary rocks are composed of limestones, marly limestones, marls and black<br>shales and have been analysed with a high-resolution stable isotope approach<br>(approximately one sample every 2 cm) combined with geochemical modelling. Using stable<br>carbon isotopes, bulk rock parameters and petrographic analysis, the onset of OAE 2 has<br>been investigated in detail. The high-resolution δ<sup>13</sup>C curve exhibits overall stable values<br>around 3 ‰ before the onset of the Plenus event. This background level is interrupted by<br>three short-lived and small but significant negative carbon isotope excursions (CIEs) down to<br>δ<sup>13</sup>C values of 2.5 ‰, 2.7 ‰ and 1.9 ‰. Immediately before the main rise in the Plenus bed,<br>a longer-lasting negative CIE down to 2.8 ‰ is observed, preceding the large positive CIE of<br>the OAE 2 to values of 5.2 ‰ over 33 ka. Thereafter, the δ<sup>13</sup>C values decrease to 3.5 ‰ over<br>a period of approximately 130 ka. The results can be correlated with the lower-resolution<br>data set of Voigt et al. (2008) but enable a more accurate characterization of the subtle<br>features of the CIE and hence events before and during this time interval. Carbon cycle<br>modelling with the modelling software SIMILE using a model based on Kump & Arthur (1999)<br>reveals that the negative excursion before the Plenus bed can be explained by a massive<br>volcanic pulse releasing of 0.95*10<sup>18</sup> mol CO2 within 14 ka. This amount corresponds to only<br>81 % of the calculated volume of CO<sub>2</sub> release during emplacement of the Caribbean LIP by<br>Joo et al. (2020). In the model the volcanic exhalation increases atmospheric CO<sub>2</sub><br>concentrations. This will increase global temperatures, intensify the hydrological cycle and<br>thus increase nutrient input into the ocean, resulting in an expansion of the oxygen minimum<br>zone, the development of anoxic conditions and an increase in the preservation potential for<br>organic material. In the model enhanced primary productivity and organic matter preservation<br>can be controlled by the implemented riverine phosphate input and the preservation factor for<br>organic matter. For the positive anomaly, the riverine phosphate input must be nearly<br>doubled (from 0.01 μmol/kg PO<sub>4 </sub>to 0.019 μmol/kg) for the period of the increasing δ<sup>13</sup>C<br>values (app. 33 ka), with a concomitant rise of the preservation factor from 1 % to 2 %. This<br>model scenario accurately reproduces the major features of the new high-resolution δ<sup>13</sup>C<br>record over the onset of the OAE 2 CIE.</p>

scholarly journals Smectite appearance in the footwall of the Úrkút manganese ore deposit, Bakony Mts., Hungary

2019 ◽  
Vol 62 (1) ◽  
pp. 100-118
Author(s):  
Máté Zsigmond Leskó ◽  
Richárd Zoltán Papp ◽  
Boglárka Anna Topa ◽  
Ferenc Kristály ◽  
Tamás Vigh ◽  
...  
Keyword(s):  
Flow System ◽  
Manganese Carbonate ◽  
Manganese Ore ◽  
Ore Formation ◽  
Ore Deposit ◽  
Oceanic Anoxic Event ◽  
The Past ◽  
Anoxic Event ◽  
Core Storage ◽  
The Relationship

The Úrkút manganese ore deposit (Transdanubian Range, Hungary) is one of the largest manganese accumulations to be formed during the Toarcian Oceanic Anoxic Event. In the past 60 years, the area was investigated intensively. The core storage facility of the manganese mine had more than 20,000 sample pieces. Most of these samples have never been investigated. During this study, which is the first widespread clay mineral study in the footwall of the Úrkút manganese ore deposit, we investigated 40 samples from seven boreholes (footwall rocks, black/gray shales below and above the first ore bed, and manganese carbonate ores). Although previous studies assumed that smectite is associated only with the ore beds, our research revealed its appearance in the footwall (Pliensbachian) as well. Simultaneously, tripoli (the local name of completely bleached chert) can also be found in the footwall. Based on the investigated samples, a sharp geochemical difference was detected between Pliensbachian and Toarcian sediments. In this paper, we try to trace the relationship between the smectite content of the footwall and the ore bed and compare these results with the observed geochemical changes. Based on the new data, we assume that the ore accumulation was caused by a flow system (upwelling-controlled ore formation).

The impact of the Pliensbachian-Toarcian crisis on belemnite diversity and size distribution

2020 ◽  
Author(s):  
Kenneth De Baets ◽  
Patrícia Rita ◽  
Luís Vítor Duarte ◽  
Pascal Neige ◽  
Laura Piñuela ◽  
...  
Keyword(s):  
High Resolution ◽  
Species Turnover ◽  
Adult Size ◽  
Oceanic Anoxic Event ◽  
Species Cluster ◽  
Anoxic Event ◽  
Major Bottleneck ◽  
Scaling Analyses ◽  
The Impact ◽  
Lusitanian Basin

<p>The Pliensbachian–Toarcian transition has been considered a major bottleneck in the early evolution of belemnites, probably related to major palaeoenvironmental and climatic changes during the Early Toarcian. Previous research has focused on the study of belemnites from higher, temperate latitudes, while high-resolution studies on diversity and size of subtropical belemnite assemblages in the northwest Tethys are comparatively rare. The lack of high-resolution (ammonoid subzone) abundance data on diversity and size distributions of belemnite assemblages does not allow separating changes during the Pliensbachian–Toarcian boundary event from those during the Toarcian anoxic event. Sample standardized diversity analyses on new data from Iberian sections suggest the Pliensbachian–Toarcian corresponds to a slight decrease in diversity and an adult size decrease within dominant species. Cluster and non-metric multidimensional scaling analyses, however, indicate that the largest changes in diversity and palaeogeographic distribution of belemnite assemblages occurred during the Toarcian oceanic anoxic event (TOAE) rather than the Pliensbachian–Toarcian boundary. In southern basins like the Lusitanian Basin and Riff Mountains, belemnites even disappear entirely during the TOAE. More generally, the TOAE corresponds with an increase in body size of belemnite assemblages driven by species turnover. The lack of widespread anoxia in southern basins of the northwest Tethys indicates that direct impact of warming or increased pCO2 triggered by volcanism as well as indirect effects on nutrient availability and productivity might have played an important role during both crises.</p>

scholarly journals High-resolution bio- and chemostratigraphy of an expanded record of Oceanic Anoxic Event 2 (Late Cenomanian–Early Turonian) at Clot Chevalier, near Barrême, SE France (Vocontian Basin)

2019 ◽  
Vol 52 (1) ◽  
pp. 97-129 ◽  
Author(s):  
Andrew S. Gale ◽  
Hugh C. Jenkyns ◽  
Harilaos Tsikos ◽  
Yvonne van Breugel ◽  
Jaap S. Sinninghe Damsté ◽  
...  
Keyword(s):  
High Resolution ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Se France

scholarly journals Red crust: evidence for an early Paleozoic oceanic anoxic event

2019 ◽  
Vol 67 (7) ◽  
pp. 995-1001 ◽  
Author(s):  
N. Langsford ◽  
T. Raimondo ◽  
J. Jago
Keyword(s):  
Early Paleozoic ◽  
Oceanic Anoxic Event ◽  
Anoxic Event

scholarly journals CO2-induced climate forcing on the fire record during the initiation of Cretaceous oceanic anoxic event 2

2019 ◽  
Vol 132 (1-2) ◽  
pp. 321-333 ◽  
Author(s):  
Sarah J. Baker ◽  
Claire M. Belcher ◽  
Richard S. Barclay ◽  
Stephen P. Hesselbo ◽  
Jiří Laurin ◽  
...  
Keyword(s):  
High Resolution ◽  
Fire History ◽  
Climate Changes ◽  
Hydrological Cycle ◽  
Geological Time ◽  
Oceanic Anoxic Event ◽  
Organic Carbon Burial ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Atmospheric Co2 Concentrations

Abstract Cretaceous oceanic anoxic event 2 (OAE2) is thought to have been contemporary with extensive volcanism and the release of large quantities of volcanic CO2 capable of triggering marine anoxia through a series of biogeochemical feedbacks. High-resolution reconstructions of atmospheric CO2 concentrations across the initiation of OAE2 suggest that there were also two distinct pulses of CO2 drawdown coeval with increased organic carbon burial. These fluctuations in CO2 likely led to significant climatic changes, including fluctuations in temperatures and the hydrological cycle. Paleofire proxy records suggest that wildfire was a common occurrence throughout the Cretaceous Period, likely fueled by the estimated high atmospheric O2 concentrations at this time. However, over geological time scales, the likelihood and behavior of fire are also controlled by other factors such as climate, implying that CO2-driven climate changes should also be observable in the fossil charcoal record. We tested this hypothesis and present a high-resolution study of fire history through the use of fossil charcoal abundances across the OAE2 onset, and we compared our records to the estimated CO2 fluctuations published from the same study sites. Our study illustrates that inferred wildfire activity appears to relate to changes in CO2 occurring across the onset of OAE2, where periods of CO2 drawdown may have enabled an increase in fire activity through suppression of the hydrological cycle. Our study provides further insight into the relationships between rapid changes in the carbon cycle, climate, and wildfire activity, illustrating that CO2 and climate changes related to inferred wildfire activity can be detected despite the estimated high Cretaceous atmospheric O2 concentrations.

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