ESTIMATION OF MINERALOGICAL, MORPHOLOGICAL, AND MAGNETIC PROPERTIES OF THE MINERAL SEDIMENTS OF GUANO CAVES IN THE KARST AREA

Abstract

Guano sediments can record environmental changes in caves and be investigated through the magnetic mineral properties contained therein. The properties of magnetic guano depend on the type, concentration, shape and size of the magnetic mineral grains. These properties can provide clues to the cave-forming environment, both lithogenic and anthropogenic influences. Therefore, this study aims to analyse the magnetic properties, mineralogy, and magnetic mineral morphology of guano sediments in caves in the karst region of Maros, Indonesia, especially Bat caves and Dream caves. Guano samples were taken according to the condition of the cave floor. Magnetic susceptibility measurements are used to analyse the magnetic properties of guano sediments. X - Ray Diffraction (XRD) and Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM - EDS) measurements were used to analyze the mineralogy and morphology of the magnetic mineral guano sediments, respectively. The results show that the magnetic susceptibility value at low frequencies ranges from (0.072 - 1.476) x 10^-6 m³ kg^-1 for Bat cave guano. The χLF value of Dream cave guano ranged from (2.867 - 85.507) x 10^-6 m³ kg^-1. The χFD (%) of Bat cave guano samples (2.78 - 8.70) %, while χFD (%) of Dream cave guano samples (0 - 4.18) %. The analysis of magnetic susceptibility, mineralogy, and magnetic mineral morphology showed that the guano samples from both caves tended to be affected by the ferrimagnetic mineral of the iron-titanium oxide group, namely magnetite (Fe₃O₄). The grain  hapes
of the guano samples from the two caves are similar; they are oval and irregular, and there are also fractures and heterogeneous grain distribution. Thus, the magnetic mineral sources in Bat cave and Dream cave guano tend to come from magnetic minerals controlled by lithogenic and anthropogenic components.