Minor and Trace Element Compositions of Carbonates Formed During Burial Diagenesis of Deltaic Sediments

Abstract

Studies of long cores of river-dominated Mississippi River delta plain sediments (Ho and Coleman, 1969; Moore et al., 1992; Bailey et al., 1998) show a varied suite of early diagenetic minerals. In general, siderite is most abundant in these sediments, followed by pyrite. These minerals vary with depth and proximity to the present coast. Pyrite and accessory calcite and dolomite appear to form early, while siderite forms later during burial diagenesis. Siderite is the predominant carbonate in inland cores and at depth in a core along the present coast. Minor calcite and dolomite are the primary carbonates present in the upper part of the coastal core. Studies of tide-dominated Mahakam River delta plain sediments (Bailey and Roberts, 1996) show an early diagenetic suite that consists of pyrite, calcite, and siderite. Calcite predominates in shallow cores, but some Pleistocene cores show siderite that resembles siderite in onshore Mississippi River Delta cores. Concretions ti'om the marine portion of the Rajang Delta also show calcite with minor siderite. Studies are being extended through collection of minor and trace element data for these concretions and examination of these data in the framework of the coastal setting and burial diagenesis.