The evolution of interdunal peat-forming environments in the Maputaland coastal plain, Mozambique

In the Elephant Game Reserve (EGR) in Mozambiquan Maputaland, several small peatlands have been developed between dunes. The aim of the study is to determine the peat-forming conditions and elucidate the evolution of the peatlands. Herbaceous vegetation (reeds and sedges) thrive on the surface of the mires. Fifty-five organic and inorganic samples were picked up from nine manually-retrieved cores up to 4.4 m deep, across several locations in the EGR. The maximum thickness of the organic sediments is 2.5 m. The determinations performed included proximate and ultimate analyses, pH and electrical Conductivity (eC) measurements, organic-petrography examination, as well as mineralogical and geochemical analyses applying X-ray diffraction and X-ray fluorescence spectrometry, respectively. The peat samples display ash yields between 10.1 and 46.8 % (on dry basis), sulphur content up to 8.9 % (db), pH and eC values from 2-7.3 and 142–2360 μS/cm, respectively. Quartz, K-feldspars and pyrite are the major minerals contained in peat; accordingly, silica is the major element with iron, aluminum, calcium and magnesium being minors. The maceral composition of peat reveals the predominance of the huminite group (57.6–78.6 vol%, on mineral matter-free basis), followed by inertinite (13.8–38.2 vol%) and liptinite (<9.6 vol%). The prevalence of the detrohuminite subgroup, particularly of attrinite, along with inertodetrinite, points to intense mechanical decomposition of the plant remains and periodical lowering of the local watertable with subsequent fires, during which the mire surface was exposed to oxidation. Overall, peat accumulation took place under rheo- to mesotrophic conditions.