High-Resolution Stratigraphic Architectures, Facies Anatomies of the Lower Cretaceous Biyadh and Shu’aiba Formations, and Their Implications on Platform Evolution and Global Correlation

2019 ◽  
pp. 3-39
Author(s):  
Nasser AL-Ghamdi ◽  
Mike Pope
Keyword(s):  
High Resolution ◽  
Lower Cretaceous ◽  
Global Correlation ◽  
Platform Evolution

scholarly journals High-resolution isotope stratigraphy of the Lower Ordovician St. George Group of western Newfoundland, Canada: implications for global correlation

2009 ◽  
Vol 46 (6) ◽  
pp. 403-423 ◽  
Author(s):  
Karem Azmy ◽  
Denis Lavoie
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Sea Level Changes ◽  
Global Correlation ◽  
Lower Ordovician ◽  
Isotope Stratigraphy ◽  
Platform Carbonates ◽  
The Baltic ◽  
Marine Platform ◽  
Bottom To Top

The Lower Ordovician St. George Group of western Newfoundland consists mainly of shallow-marine-platform carbonates (∼500 m thick). It is formed, from bottom to top, of the Watts Bight, Boat Harbour, Catoche, and Aguathuna formations. The top boundary of the group is marked by the regional St. George Unconformity. Outcrops and a few cores from western Newfoundland were sampled at high resolution and the extracted micritic materials were investigated for their petrographic and geochemical criteria to evaluate their degree of preservation. The δ13C and δ18O values of well-preserved micrite microsamples range from –4.2‰ to 0‰ (VPDB) and from –11.3‰ to –2.9‰ (VPDB), respectively. The δ13Ccarb profile of the St. George Group carbonates reveals several negative shifts, which vary between ∼2‰ and 3‰ and are generally associated with unconformities–disconformities or thin shale interbeds, thus reflecting the effect of or link with significant sea-level changes. The St. George Unconformity is associated with a negative δ13Ccarb shift (∼2‰) on the profile and correlated with major lowstand (around the end of Arenig) on the local sea-level reconstruction and also on those from the Baltic region and central Australia, thus suggesting that the St. George Group Unconformity might have likely had an eustatic component that contributed to the development–enhancement of the paleomargin. Other similar δ13Ccarb shifts have been recorded on the St. George profile, but it is hard to evaluate their global extension due to the low resolution of the documented global Lower Ordovician (Tremadoc – middle Arenig) δ13Ccarb profile.

Palaeoenvironmental significance of storm coquinas in a Lower Cretaceous coastal lagoonal succession (Vectis Formation, Isle of Wight, southern England)

2000 ◽  
Vol 137 (2) ◽  
pp. 193-205 ◽  
Author(s):  
JONATHAN D. RADLEY ◽  
MICHAEL J. BARKER
Keyword(s):  
High Resolution ◽  
Principal Components ◽  
Lower Cretaceous ◽  
Coastal Lagoons ◽  
Trace Fossils ◽  
Isle Of Wight ◽  
Southern England ◽  
Desiccation Cracks ◽  
Stratigraphic Framework

Thin bioclastic limestone beds (‘coquinas’) in the Vectis Formation (Wealden Group, Lower Cretaceous) of the Isle of Wight, southern England, exhibit a range of biofabrics and internal stratigraphies. These features are attributed to both simple and complex storm deposition of allochthonous biogenic and siliciclastic materials in coastal lagoons and on adjacent mudflats. These modes of deposition facilitated preservation of dinosaur trackways, desiccation cracks, shallow-tier trace fossils and in situ bivalve colonies through rapid burial. The coquinas thus preserve a record of surficial muds, commonly lost through reworking. The principal components of the coquinas comprise dispersed elements from within the argillaceous ‘background’ facies. Some of these beds are laterally traceable for up to 27 km, providing the foundations for a high-resolution event-stratigraphic framework.

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