Pengaruh Perbedaan Kondisi Mire terhadap Karakteristik Gambut di Lahan Gambut Mahakam Tengah - Delta Sungai Mahakam, Kalimantan Timur

Taufiq Aryo Wibowo, Prof. Dr. Ir. Ferian Anggara, S.T., M.Eng., IPM. ; Dr.Ing. Ir. Donatus Hendra Amijaya, S.T., M.T., IPM.

2026 | Skripsi | TEKNIK GEOLOGI

Penelitian ini dilakukan pada lahan gambut Mahakam Tengah hingga Delta Sungai Mahakam, Kalimantan Timur, yang merepresentasikan tiga kondisi mire berbeda, yaitu Danau Semayang, Sungai Bilas, dan Delta Mahakam. Penelitian ini bertujuan untuk mengetahui pengaruh perbedaan kondisi mire terhadap karakteristik fisik, kimia, dan petrologi organik gambut. Pengambilan sampel dilakukan melalui pengeboran dengan interval 50 cm hingga mencapai dasar gambut. Sampel gambut dideskripsi secara megaskopis berdasarkan klasifikasi tekstural gambut (Wust dkk., 2003), kemudian dianalisis menggunakan analisis proksimat, ultimat, dan petrologi organik. Perbedaan karakteristik gambut antarlokasi dievaluasi menggunakan uji non-parametrik Kruskal-Wallis dan dilanjutkan dengan Dunn Test untuk mengetahui pasangan lokasi yang berbeda signifikan.

Hasil penelitian menunjukkan bahwa gambut Danau Semayang terbentuk pada ombrotrophic mire di lingkungan lacustrine inland, Sungai Bilas terbentuk pada rheotrophic mire di lingkungan fluvial-deltaic, sedangkan Delta Mahakam terbentuk pada rheotrophic mire di lingkungan deltaic coastal. Danau Semayang dan Sungai Bilas didominasi oleh gambut sapric, partikel halus, matrix, dan maseral humodetrinite yang menunjukkan tingkat degradasi material organik lebih tinggi. Sebaliknya, Delta Mahakam didominasi oleh gambut hemic hingga fibric, partikel lebih kasar, jaringan wood, serta maseral textinite, corpohuminite, dan suberinite yang menunjukkan preservasi jaringan tumbuhan lebih baik. Hasil uji Kruskal-Wallis menunjukkan perbedaan signifikan pada kadar abu, kadar lengas, nitrogen, dan sulfur, sedangkan karbon dan hidrogen tidak menunjukkan perbedaan signifikan antarlokasi. Kadar abu tertinggi terdapat pada Sungai Bilas (median 57,34 wt.%), diikuti Delta Mahakam (median 44,72 wt.%), dan terendah pada Danau Semayang (median 8,19 wt.%).

Mire dengan pengaruh sungai dan suplai sedimen lebih kuat cenderung menghasilkan gambut dengan kandungan material anorganik lebih tinggi, sedangkan mire air tawar yang lebih stabil menghasilkan gambut yang lebih terdekomposisi dengan kadar abu lebih rendah. Pada Delta Mahakam, pengaruh sistem deltaik dan pasang surut mendukung akumulasi material organik kasar serta preservasi jaringan tumbuhan. Perbedaan kondisi mire mengontrol karakteristik gambut melalui variasi hidrologi, kestabilan genangan, suplai sedimen, tingkat dekomposisi, serta pengaruh aliran sungai dan pasang surut laut.

This study was conducted in the peatland area of Central Mahakam to the Mahakam River Delta, East Kalimantan, which represents three different mire conditions, namely Semayang Lake, Bilas River, and the Mahakam Delta. This study aims to determine the influence of different mire conditions on the physical, chemical, and organic petrological characteristics of peat. Peat sampling was carried out by drilling at 50 cm intervals until the base of the peat was reached. The peat samples were megascopically described based on the textural classification of peat by Wust et. al., (2003), and were then analyzed using proximate, ultimate, and organic petrology analysis. Differences in peat characteristics among locations were evaluated using the non-parametric Kruskal-Wallis test, followed by Dunn’s Test to identify significantly different location pairs.

The results show that the peat of Semayang Lake formed in an ombrotrophic mire within a lacustrine inland environment, Bilas River formed in a rheotrophic mire within a fluvial-deltaic environment, whereas the Mahakam Delta formed in a rheotrophic mire within a deltaic coastal environment. Semayang Lake and Bilas River are dominated by sapric peat, fine particles, matrix, and humodetrinite macerals, indicating a higher degree of organic material degradation. In contrast, the Mahakam Delta is dominated by hemic to fibric peat, coarser particles, wood tissue, as well as textinite, corpohuminite, and suberinite macerals, indicating better preservation of plant tissues. The Kruskal-Wallis test results show significant differences in ash yield, moisture content, nitrogen, and sulfur, whereas carbon and hydrogen do not show significant differences among locations. The highest ash yield occurs in Bilas River (median 57.34 wt.%), followed by the Mahakam Delta (median 44.72 wt.%), and the lowest in Semayang Lake (median 8.19 wt.%).

Mires with stronger river influence and sediment supply tend to produce peat with higher inorganic material content, whereas more stable freshwater mires produce more decomposed peat with lower ash yield. In the Mahakam Delta, the influence of the deltaic system and tides supports the accumulation of coarse organic material and the preservation of plant tissues. Differences in mire conditions control peat characteristics through variations in hydrology, waterlogging stability, sediment supply, degree of decomposition, and the influence of river flow and tidal processes.

Kata Kunci : gambut, mire, Danau Semayang, Sungai Bilas, Delta Mahakam, karakteristik gambut.