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ABSTRACT: Unexpected Evaporites within the Terrestrial Strata of the Passaic Formation, Newark Basin, New Jersey: Significance in Basin Analysis

EL TABAKH, MOHAMED, and B. CHARLOTTE SCHREIBER, Queens College, Flushing, NY, and PAUL OLSEN, Lamont-Doherty Geological Observatory, Columbia University, Palisades, NY

The variation in the types, quantities and mode of occurrence of evaporites in the Passaic Formation makes it possible to understand a part of the paleoenvironmental evolution of the Newark rift basin because their sedimentological, geochemical, and early diagenetic aspects are directly linked to variations in the basin paleohydrology and also to the area of the depositional surface of the basin. The Passaic Formation is about 11,000-ft thick and is composed of terrigenous mudstones, siltstones, shales, evaporites, and limestones that interfinger at the basin margins with coarser clastic deposits. The quantity of evaporite sediments increases upwards through the section, showing a cyclic patterns in distribution and a diversity in crystal morphology.

Four drilled cores of the Newark basin continental drilling project (1990-1991) sampled approximately 10,000 ft of the Passaic Formation (1,000 ft remains unsampled). The lower 2,000 ft contains evaporites found as disseminated fine cements and 1-2 mm-sized blebs. The middle 6,000 ft contains large amounts of evaporites (30-40%) mostly present as pseudomorphs of various evaporite crystal forms that are found as massive beds and as disseminated coarse crystals (1-5 cm long). In the upper 2,000 ft of the formation, evaporites are less common than in the middle section, and are present as bedded nodular forms. These evaporites are indicative of evolving water composition due to both changing input and selected ionic depletion that are the product of the evolving basinal morphology and as ociated drainage system as well as the more general climatic forcing cycles.

 

AAPG Search and Discovery Article #91013©1992 AAPG Eastern Section Meeting, Champaign, Illinois, September 20-22, 1992 (2009)