Abstract
Paleoecology of some Upper Cretaceous Formations from Selected Wells Northwest and Middle Iraq
Highlights
On the basis of the biocontents, lithological features and analysis of the microfacies, an attempt is made to establish the nature of paleoecology and depositional environments of some Upper Cretaceous formations from northwest and middle Iraq,of which the successions are represented by the formations from the oldest to the youngest are Khasib, Tanuma, Sa'di, Mushorah, Hartha and Shiranish
From the evidence presented above the paleoecology of Khasib Formation is characterized by well oxygened in a deep marine environment extend from the middle-outer shelf to the upper slope in the lower and middle parts and shallow marine environment appeared in some positions in the middle parts
The paleoecology of the Tanuma Formation represents the shelf environment; concentrated mainly in the inner and middle shelf; reflecting shallow marine to subbasinal environments which characterized by the anoxic conditions
Summary
AccoFridgi.5ng: StotrMatiognroapsthoirci s(e1c9t8io5n) othfeupppriemr aCryreataimceooufsthfoeremnavtiiroonnsminenwtaelllsDtudies by using Ostracode is to determine the association indicating former environmental types. The subdivision of marine environments from Sliter, 1985; Koutsoukos and Hart, 1990 (Fig. 6) was found more comprehensive and specific than the former subdivision .The applications of Ostracode as an indicator for paleobathymatery have been emerged through the basic following principles: 1- Index genera. Presence of Parakrithe in the lower and middle parts of the formation and the high proportion of individuals indicates deep water marine environment (Van Morkhoven, 1963). The occurrence of Hedbergella and Heterohelix which indicates continental shelf (outer shelf) environment (Sliter, 1972).In addition, different groups of faunas such as algae, bryozoa, calcisphere, sponge spicules, echinoderms and pelecypodes are present within the dominant grainstone facies in the upper parts of the formation indicates shallow water environment. The conformability of the distinguished facies from the present study with SMF types 2, 3, 6, 8, 9, 12 deposited within the FZ 1, 2, 3, 4, 6, 7 with model of (Wilson,1975) modified by (Flügel, 1982) suggested a widespread distribution of basinal and basin margin environments in particular in the lower and mid parts of the formation with the foreslope, winnowed platform and open platform as a depositional environments in the upper parts
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