SULFUR IN THE CHANGUINOLA PEAT DEPOSIT, PANAMA, AS AN INDICATOR OF THE ENVIRONMENTS OF DEPOSITION OF PEAT AND COAL

The sulfur (S) content of coal is often used to infer aspects of paleo climate, tSophic state, and proximity to marine influence, of the mire in which it was deposited. In this study, the S content of peat in a large back-barrier mire complex on the Caribbean coast of Panama is re lated to climatic, biological, and tectonic factors of the depositiona l environment. Earthquake-generated subsidence is greatest to the sout heast, leading to drowning of the deposit beneath Almirante Bay, and 4 0% of the peat is now below sea level, Coastal mangrove peats with mod erately high S content (1-5 wt % S) and high salinity (> 1.0 wt %) dom inate the eastern margin and extend beneath the salt water and shallow marine sediments of the adjoining bay. Marine influence extends only a short distance onshore, except in the vicinity of brackish blackwate r creeks that drain the swamp. Peats associated with these tidal chann els are low in salinity (< 1.0 wt %) and very high in S (5 to similar to 14 wt % S), apparently the result of a biogeochemical chain of S re actions leading to the concentration of C-S sulfides. The western part of the deposit is domed, and the vegetation and the peat are concentr ically zoned. Stunted, sawgrass-dominated vegetation that produces fib ric, very low S (< 0.25 wt % S) peat occupies the central bog plain. A round the bog plain, mixed-forest and palm-forest swamps produce dense hemic and fine hemic peat with higher S content (0.25-0.5 wt % S). Th e S content is in proportion to the degree of humification of the peat , and both are independent of the pH of the groundwater, The distribut ion of forms of organic and inorganic sulfur in the tropical peats are found to be comparable to published values for temperate and subtropi cal peats, despite differences in vegetation and climate. The distribu tion of high-sulfur peats in the eastern part of the deposit and low-s ulfur peats in the western part, and the SE-NW transgression parallel to the trend of the coastline, reflects the regional structural trend of coseismic subsidence greatest to the southeast.