STUDI KETIDAK SELARASAN ANTARA TANAH DAN BATUAN KARBONAT YANG MEMBAWAHINYA PADA JALUR BARON – WONOSARI GUNUNGKIDUL
Abstract
Tujuan penelitian adalah mengaji ketidakselarasan antara tanah dan batuan karbonat yang
membawahinya. Analisis baik tanah maupun batuan karbonat meliputi komposisi mineral dan kimia. Komposisi
mineral fraksi pasir tanah di atas batugamping dirajai oleh labradorit sedangkan fraksi lempungnya oleh haloisit
dan kaolinit. Kristobalit juga dijumpai terutama pada tanah-tanah di lingkungan karst. Berdasarkan macam
mineral tersebut diduga bahan induk tanah banyak dipengaruhi oleh bahan volkanik. Komposisi batugamping
dirajai kalsit dan kuarsa. Terdapat perbedaan yang tegas antara komposisis mineral tanah dan batugamping,
nisbah Fe tanah dan batugamping sangat rendah, adanya lithic contact yang sangat tegas. Terdapat mintakat
pelapukan napal yang membawahi tanah, nisbah Fe tanah/ napal jauh lebih tinggi dibanding terhadap
batugamping, kadar CaCO3 napal rendah, dan baik tanah mapun napal mengandung smektit sehingga dikatakan
bahwa napal bersifat mewariskan pada tanah yang terbentuk. Labradorit juga melimpah pada tanah di atas napal.
Berdasarkan faktor-faktor tersebut maka disimpulkan bahwa ada ketidakselarasan antara tanah dan batugamping
yang membawahinya kecuali pada napal. Bahan volkanik sangat berpengaruh sebagai bahan induk tanah.
Kata kunci: batuan karbonat, bahan volkanik, batugamping, tanah, ketidakselarasan
ABSTRACT
The aim of research was to study of the unconformity of soil–carbonate rock underlying relationship.
Analysis both soil and carbonate rock cover minerals and chemical composition. Sand fraction mineral
composition of soil overlying limestone dominated by labradorite whereas clay fraction by halloysite and
kaolinite. Chrystobalite also was found especially on soils of karst area. Based of those minerals, soil parent
material predicted much be influenced by volcanic material. Limestone mineral composition dominated by
calcite and quartz. There are distict differences of carbonate mineral composition and soils, ratio Fe of soil/
limestone is very low, and there is a sharply lithic contact of soil and limestone underlying. Soils overlying marl
show paralithic contact, there is a zone of marl weathering, and ratio Fe of soil to marl is higher than ratio Fe of
soil to limestone, and CaCO3 concentration lower than limestone. Both soils and marl underlying contain
smectite. Based factors above be said that marl have inheritate characteristic. Sand fraction minerals of soil
overlying marl are also dominated by labradorite. Based on boundary of soil and rock material underlying and
kind of minerals concluded that there are unconformity between soils and limestone underlying, but relationship
between soils and marl underlying are conformity. Soils underlying carbonate material much be influenced by
volcanic material.
Key words: carbonate, volcanic materials, limestone, soil, unconformity
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