BIOSTRATIGRAPHY OF CRETACEOUS- TERTIARY BOUNDARY IN SOUTHWESTERN OF TRIPOLI/SABRATH BASIN OFFSHORE LIBYA (CONCESSION NC41)

Abstract

The present study deals with Cretaceous- Tertiary unconformity in the southwestern part of the Tripoli- Sabratha Basin Off-Shore Libya (Concession 41). A detailed biostratigraphic study has mainly carried out by means of ditch cutting samples analysis from five wells: F1, N1, G1, P11and K1 NC41. Successive sediments above and below the Cretaceous / Tertiary boundary are related to the following formation: Metlaoui Formation, El Haria Formation (A&B Members), Abiod Formation, Aleg Formation, Doulelb Equivelant Formation and Zebbag or Zebbag Eq. Formation, that have a wide distribution in both  Off-Shore Libya and Tunisia Biostratigraphic analysis led to the identification of Upper and Lower Paleocene Bio-Zones, according to the biostratigraphic scheme proposed by Agip (1985) for the Mediterranean area.

In the study area the duration of the Cretaceous / Tertiary hiatus increases from east to west. The South- eastern side of NC41 (well F1) has a minimum hiatus of the Cretaceous/Tertiary unconformity. In the South-western side (Wells N1, G1, P1, &K1) the Cretaceous/Tertiary unconformity increases to reach the maximum hiatus in Well P1 where the Conacian/Santonian sediments (Douleb Eq) are overlain by the Lower Eocene sediment (Metlaoui Formation). Absolute value of the Cretaceous / Tertiary hiatus can be estimated by absence of successive bio-zones. Consequently, minimum approximates to 2 MY marked in Well F1, and maximum hiatus approximates to 30 MY marked in Well P1.

The occurrence and relative abundance of planktonic and several benthic foraminiferal taxa can be used to recognize the depositional environments. During most of the Upper Cretaceous and Lower Paleocene deep marine conditions prevailed. Conversely, the Lower Eocene was mainly characterized by shallow marine conditions.