<b>Comparison of authigenic minerals in sandstones and interbedded mudstones, siltstones and shales, East Berlin formation, Hartford Basin, USA</b>

Abstract

The East Berlin formation consists mainly of alternating sequences of fluviatile, lacustrine and playa sediments. Diagenetic sequences reconstruction revealed the same range of authigenic minerals in the studied sandstones and the interbedded fine-grained sediments (mudstones and siltstones). This indicates that the diagenetic processes that took place in the sandy facies also took place in fine-grained sediments. Mechanically infiltrated clays, grain-coating clay/hematite, quartz and feldspar overgrowths, carbonate cements and pore-filling and pore-lining clay minerals that precipitated in the sandy facies also precipitated in the fine-grained sediments. The abundance of authigenic minerals in decreasing order include: sandstone > siltstone > mudstone > shale. Except minor amounts of authigenic illite-smectite and illite, the shaly facies dominated by detrital clay, carbonate, quartz and feldspars framework grains. Authigenic minerals such as quartz, albite and K-feldspar are absent in the shaly facies, possibly related to early destruction of porosity. The lacustrine sandstones, siltstones and mudstones followed marine diagenetic trend, whereas playa and fluviatile sandstones, siltstones and mudstones followed red bed diagenetic trend. Mechanically compacted mudstones, siltstones and shales expelled large volume of mineralized pore water, which might migrated into the sandstone-rich section. Part of the ions for the precipitation of quartz overgrowths and carbonate cements in the sandy facies possibly contributed from the interbedded siltstones, mudstones and shales facies.

KEY WORDS: Authigenic minerals, Mudstone, Sandstone, Siltstone, East Berlin formation, Hartford Basin

Bull. Chem. Soc. Ethiop. 2007, 21(1), 39-61.