scholarly journals Radiolarian Age Constraints of Mid-Cretaceous Black Shales in Northern Tunisia

10.5772/34707 ◽  
2012 ◽  
Author(s):  
Ben Fadhel ◽  
Soua Mohamed ◽  
Zouaghi Taher ◽  
Layeb ◽  
Mohsen ◽  
...  
Keyword(s):  
Black Shales ◽  
Northern Tunisia ◽  
Age Constraints

Geochronologic constraints on the Shuram excursion in Oman

2020 ◽  
Author(s):  
Marjorie Cantine ◽  
Alan Rooney ◽  
Ulf Linneman ◽  
Mandy Hofmann ◽  
Richard Albert ◽  
...  
Keyword(s):  
Inner Core ◽  
Black Shales ◽  
Depositional Environments ◽  
Driving Mechanism ◽  
Global Correlation ◽  
Carbon Isotope Excursion ◽  
Icp Ms ◽  
Absolute Age ◽  
Low Magnetic Field ◽  
Age Constraints

<p>            The rise of animals occurred during an interval of Earth history that witnessed highly dynamic atmosphere-ocean redox conditions; regional, transient glaciations; extraordinarily low magnetic field intensities potentially related to inner core formation; and perturbations to the global carbon cycle of a size not seen before or since. The largest of these, the Shuram carbon isotope excursion, has been invoked as a driving mechanism for, or consequence of, various biological and geological events during the Ediacaran Period. However, there are a number of major controversies regarding the Shuram, including its timing. Without age constraints on its onset or duration, it is impossible to confidently connect the Shuram Event with any biological or geological upheavals.</p><p>Here, we apply multiple methods, including Re-Os on black shales and U-Pb LA-ICP-MS dating on carbonates, to well-preserved Ediacaran stratigraphy from Oman, deriving new age controls in previously undated parts of the stratigraphy. Our new data show that paired Re-Os shale and U-Pb carbonate analyses constrain the onset and duration of the Shuram excursion in Oman. The results—which are consistent with recent age constraints on Shuram-bearing stratigraphy from Northwest Canada (Rooney et al. 2019, Goldschmidt)—demonstrate the utility of leveraging multiple geochronological techniques within a single basin to constrain deposition in deep to shallow depositional environments. The results also provide key absolute age constraints on the onset of the Shuram excursion in the stratigraphy where it was first defined, critical for testing global correlation schemes, constructing a temporal framework for the Ediacaran period, and identifying causal mechanisms during this interval of geobiological and geodynamic dynamism.</p><p> </p>

The Upper Cenomanian-Turonian (Upper Cretaceous) of the Saharan Atlas (Algeria)

2008 ◽  
Vol 179 (6) ◽  
pp. 593-603 ◽  
Author(s):  
Danièle Grosheny ◽  
Fettouma Chikhi-Aouimeur ◽  
Serge Ferry ◽  
Fatiha Benkherouf-Kechid ◽  
Mohamed Jati ◽  
...  
Keyword(s):  
Sea Level ◽  
Black Shale ◽  
Black Shales ◽  
Carbonate Platforms ◽  
Northern Tunisia ◽  
The North ◽  
Western Interior Basin ◽  
Platform Carbonates ◽  
Saharan Platform ◽  
Reference Section

Abstract A series of sections from the Ouled Nail, Hodna and Aurès massifs of Algeria have been studied to analyse the palaeogeographic evolution of the eastern part of the Saharan Atlas prior to and after the Cenomanian/Turonian (C/T) boundary event. Three periods are distinguished in the interval studied. During the middle to late Cenomanian, an overall ramp setting prevailed from the Saharan platform to the deeper environments of the Saharan Atlas. The latest Cenomanian and the earliest Turonian was marked by an episode of marked palaeogeographic change. Prior to the deposition of C/T boundary black shales, a rise in sea level occurred. Shallow-water carbonates were locally able to accommodate the sea-level rise. A “keep-up” response created a palaeogeography made up of isolated carbonate platforms separated by saddles, where a 1–20 m thick bed of deeper water mudstones was deposited as the lateral equivalent of the platform carbonates. At a larger scale, these saddles probably acted as corridors that allowed marine communication with the intra-Saharan basins (Tinrhert, Tademaït basins). Correlations show that the boundary black shales later filled up the saddles of the Saharan Atlas, and onlapped the carbonate platforms, before the deposition of lower Turonian open marine marls that everywhere blanket the successions. During the early to late Turonian, the palaeogeography again changed to restore a N-S oriented ramp setting, similar to that of the middle Cenomanian. Correlation with the deeper-water facies of nearby northern Tunisia, suggests that the uppermost Cenomanian mudstone immediately underlying the black shale facies in the Saharan Atlas is the lateral equivalent of the uppermost bed of the Fahdene Formation (the so-called “pre-Bahloul”) underlying the Bahloul black shale facies in the Tunisian Kalaat Senan reference section. Our platform-to-basin correlations show that the base of this bed is a regional transgressive surface, not a type II sequence boundary as suggested by previous authors. Finally, it is proposed that this mudstone bed correlates with Bed 63 of the Pueblo global reference section in the North American western Interior Basin, which also marks the beginning of the strong C/T boundary transgression.

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