Kuzey Zelten Platformunda (Sirt Baseni, Libya) Kretase Dönemi Periyodik Transgresif ve Regresif Sekansları

Yıl 2010, Cilt: 25 Sayı: 4, 9 - 16, 01.12.2010

Senusi M. Harsha

Öz

Kretase döneminde iki adet denizel ilerleyen ve gerileyen istif yer almaktadır. Biri Sirt bölgesi hala yay konumunda olduğu Erken Kretase’yi temsil ederken diğeri de Erken Üst Kretase ‘nin başlangıcı ve Üst Kretase (Kampaniyen) ‘de ki, Kuzey Tibesti‐Sirt yükseliminin sona ermesinden sonrasını temsil etmektedir. Maestrichtian denizi, ilk sellenme yüzeyini kuzeyden gelerek şekillendirmiştir. Yukarı doğru gittikçe, gerileyen ve sığlaşan özellik gösteren Kalash Formasyonuna ait karbonatlardan daha önce oluşan koyu gri şeyler (Sirt şeyli) hendekte çökelmişlerdir. Hidrokarbonlar, Kretase yaşlı hazne kayaçlar ve alttaki Kambroordovizyen yaşlı Gargaf kumtaşları içerisinde hapsolmuşlardır. Sirt şeylleri bu hidrokarbonlar için hem örtü ve hem de hazne kayaç özelliği taşımaktadır. Alttan üste doğru Üst Kretase yaşlı formasyonlar, Bahi, Sirt ve Kalash formasyonlardır.

Anahtar Kelimeler

İstif, Bahi, Sirt ve Kalash, Sirt, Libya

CYCLIC TRANSGRESSIVE AND REGRESSIVE SEQUENCES DURING CRETACEOUS TIME, NORTHERN ZELTEN PLATFORM, SIRT BASIN, LIBYA

Öz

Two marines transgressive and regressive cycles are recognized during the Cretaceous time; one is represented during Early Cretaceous, when the Sirt area was still an arch. In this cycle, the sedimentation had only taken place on the line base of the arch. The Jurassic sediments partially transgressed the arch but had their depositional edge on the flank of the arch. The other cycle is represented after the northern Tibesti‐Sirt uplift collapsed in the beginning of the Early Upper Cretaceous and during the Upper Cretaceous (Campanian) time. The Maestrichtian Sea encroached from the North and further to design the first flooding surface in the area. Thick of dark grey shale (Sirt Shale) followed by deposition of shallowing upward regressive carbonate of the Kalash Formation were deposited in the troughs. The Sirt shale acts as both a seal and source rocks for hydrocarbons trapped in the Cretaceous reservoirs and underlying the Cambro‐Ordovician Gargaf Sandstone. The Upper Cretaceous formations are Bahi, Sirt, and Kalash in ascending order. The top of the Kalash Limestone marks the Maestrichtian/ Danian boundary in the study area.

Anahtar Kelimeler

Sequence, Bahi, Sirt ve Kalash, Sirt, Libya.

Kaynakça

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