Physiography of Coastal Sediments and Development of Potential Soil Acidity1
- L. J. Pons,
- N. Van Breemen and
- P. M. Driessen2
Potentially acid sedimentary material contains pyrite in excess of acid-neutralizing substances. Formation of such material requires (1) ingredients for pyrite formation (sulfate, sulfate reducers, organic matter, iron, and anaeroby alternating with limited aeration), (2) low contents of acid-neutralizing substances, and (3) removal of dissolved alkalinity formed during sulfate reduction. Intertidal environments with mangroves or reeds are particularly favorable for pyritization of ferric iron. Highest pyrite contents build up where tidal flushing is strong. Rapid rises in relative sea level, as after the last glaciation, caused deposition of extensive, thick and highly pyritic sediments (examples: interior parts of the Chao Phraya, Mekong and Orinoco deltas, parts of Sumatra, old sea clay of Holland). After stabilization of the sea level, some 5,000 years B.P., pyrite contents remained low where high rates of sedimentation and coastal accretion caused a rapid shift of the intertidal zone (Irrawaddy and Mekong deltas, Guyana coast). High pyrite contents in the most recent sediments are associated with low sedimentation rates (e.g., along the Saigon, Niger, and Gambia rivers), or with a high density of tidal creeks. In humid climates very low sedimentation rates result in the formation of pyritic peaty material on top of older pyritic clay (Niger delta, western Netherlands).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 1982. . Copyright 1982 by the Soil Science Society of America, Inc., 5585 Guilford Rd., Madison, WI 53711 USA