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ABSTRACT: Structural, Depositional, And Diagenetic Analysis of the Pennsylvanian Morrow within the Cedar Lake Area in the Delaware Basin of Southeast New Mexico


In the Delaware Basin of southeast New Mexico, the Lower Pennsylvanian Morrow sandstones can be divided into two distinct facies, called the Lower Morrow and Middle Morrow, separated by a widespread radioactive marine unit called the Middle Morrow Shale. The Lower Morrow interval is generally characterized by coarse grained sandstones which often lack the normal coarsening upward pattem usually deposited in a deltaic environment. This study indicates that the Lower Morrow represents a low-sinuosity, coarse-grained fluvial system. The deltaic environment in the Lower Morrow interval observed is characterized by backstepping, retrogradational parasequences, with transgressive lags at the top and bottom of each parasequence. The Pennsylvanian sandstones rests unconformably on the Mississippian surface, known as the Barnett and/or the Chester. The upper facies, called the Middle Morrow is dominated by fine-grained sandstones and displays a coarsening-upward pattem. The Middle Morrow interval's deltaic sequence displays a more typical progradational parasequence pattern building toward the basin. In Pennsylvanian Morrow sands, the primary loss of porosity is due to pressure solution and silicification. Generally, the poor discovery rate and productivity in the Pennsylvanian Morrow sands has been due to complexities of the fluvial-deltaic environment and complex structural and tectonic elements. Strike-slip faulting has overprinted the normal and reverse faulting in the area creating small- to moderate-sized reservoir targets. This research has integrated the complex structural, environmental and diagenetic elements displayed in the Pennsylvanian Lower and Middle Morrow in the Cedar Lake area of southeast New Mexico.

AAPG Search and Discovery Article #90947©1997 AAPG Southwest Section Meeting, San Angelo, Texas