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ABSTRAKAir tanah merupakan sumber utama cadangan air tawar yang bekerja dalam siklus hidrostatik. Air tanah disediakan untuk konsumsi manusia, pertanian, industri dan banyak ekosistem yang bergantung pada air tanah, terutama selama musim kemarau. Kecamatan Hulonthalangi secara geografis terletak bagian selatan Kota Gorontalo berbatasan langsung dengan Teluk Tomini terdiri dari 5 kelurahan yakni Donggala, Pohe, Siendeng, Tenda dan Tanjung Kramat. Jumlah penduduknya 16.304 yang dilalui tiga sungai yakni Sungai Bone, Bolango dan Tamalate. Penelitian ini bertujuan mengetahui kedalaman muka air tanah dangkal secara pasti dengan mengukur langsung sumur warga. Selain itu penelitian ini juga bertujuan mengetahui kualitas air tanah dengan analisis parameter fisika dan kimia. Metode yang digunakan adalah analisis secara kualitatif dan kuantitatif. Analisis kualitatif mengamati kualias air tanah berdasarkan parameter fisika seperti warna, bau, rasa dan keterdapatan endapan serta mewawancara warga. Untuk analisis kuantitatif mengukur dan memplot koordinat, elevasi, kedalaman air tanah dan kandungan kimia. Hasil dan pembahasan penelitian menunjukan kedalaman muka air tanah rata-rata 2,87 - 4,04 meter. Pola aliran air tanah terbagi dua yakni dari tenggara ke barat laut dan dari timur ke barat. Analisis kualitas air, untuk warna 16% sampel terindikasi perlu tindaklanjut analisis laboratorium. Parameter bau 12% sampel tidak memenuhi syarat, untuk rasa 24% sampel tidak memenuhi syarat dan untuk endapan 14% sampel terindikasi tindaklanjut analisis laboratorium. Pemanfaatan air tanah 24% untuk kebutuhan pokok temasuk air minum. Analisis kimia di Stasiun 46 Kelurahan Pohe merupakan depot air minum mengandung besi 0,02 mg/l, nitrat 1,2 mg/l dan arsen 0 mg/l memenuhi standar kesehatan. ABSTRACT Ground water is the main source of freshwater reserves that work in the hydrostatic cycle. Groundwater is provided for human consumption, agriculture, industry and many ecosystems that depend on ground water, especially during dry seasons. Hulonthalangi Subdistrict is geographically located south of Gorontalo City adjacent to Tomini Bay consists of 5 villages namely Donggala, Pohe, Siendeng, Tenda and Tanjung Kramat. The population of 16,304 passes through three rivers namely Bone, Bolango and Tamalate Rivers. This study aims to determine the depth of shallow groundwater face with certainty by directly measuring the residents' wells. In addition, this study also aims to determine the quality of groundwater with the analysis of physical and chemical parameters. The method used is qualitative and quantitative analysis. Qualitative analysis observes the quality of groundwater based on physical parameters such as color, odor, taste and sediment deposit and interviewing citizens. For quantitative analysis measures and ploting the coordinates, elevation, depth of ground water and chemical content. Results and discussion of the study showed the depth of groundwater averaging 2.87 - 4.04 meters. The pattern of groundwater flow is divided into two, namely from southeast to northwest and east to west. Analysis of water quality, for the color of 16% samples indicated need follow-up laboratory analysis. The odor parameter of 12% samples was not eligible, for a taste of 24% unqualified samples and for precipitation 14% samples indicated follow-up laboratory analysis. Utilization of ground water 24% for basic needs including drinking water. Chemical analysis at Station 46 Pohe Village is drinking water depot contain 0.02 mg/l iron, 1.2 mg/l nitrate and 0 mg/l arsen meets health standards.

The potential of reef limestone in Gorontalo Province is very large. The proof is in two research stations in Kelurhan Buli'ide and Tanjung Kramat Village. Research on the potential of reef limestone using two methods of analysis petrology and geochemistry of XRF. Based on the results of the research both stations have the name of the rock and the composition of the chemical compounds is different. The results of the study differ from previous studies. Differences are found in the composition of CaO compounds higher than 80%. The chemical composition of compounds in two research stations has the potential to be developed into industrial material. Use of reef limestone can be used as building stones, road stabilizers, agricultural lime, ceramic materials, water purification and the process of deposition of non-ferrous metal ores.

The research location is the northern part of the Basin of Limboto Lake; the focus of the research is the limestone outcrop with 24 meter thickness in Yosonegoro area. The purpose of the study is to find out facies, standard microfacies and depositional environment on Limboto limestone. The research method carried out consisted of three methods namely the measured section, petrographic analysis and biostratigraphy analysis. The limestone facies in the Yosonegoro area consist of two facies. Then, based on sedimentary structure, composition, color, precipitation texture, terrestrial origin components and the organism content, the two facies can divided into three different microfacies. Paleobathymetry shows a deepening from the middle shelf-upper slope to the upper slopelower slope due to the sea level rise. Compilation of standard microfacies and paleobathymetry types shows changes in depositional environment from the slope environment to the toe of slope environment. The result of this study will be led researchers to propose the name of the new formation, which is the Limboto Limestone Formation according to specific location and characteristics from the previous formation name of the Clastic Limestone Formation.

The research area is located in northern Limboto Lake in Gorontalo Province, which has complex geological characteristics. The geological complexities include stratigraphy and tectonics which influence the formation of the Limboto Basin. Limestone research in the Late Tertiary Limboto Basin is very intriguing to be done because of the lack of research in limestone. Gorontalo limestone outcrops, which become the focus of the research, have a total thickness of 30 meters. The research objective is to analyze facies, microfacies, and depositional environment of tertiary limestone. These two research objectives are attained by using two research methods, namely measurd section and petrography analysis. The research result exhibits that there are four Gorontalo limestones facies, including coralline rudstone intercalated with thin mudstone facies, sandy micrite intercession facies, coralline rudstone intercession facies and sandy allochem limestone intercession facies. According to the limestone micro- facies standard, the depositional environment of Gorontalo limestone is platform interior restricted (facies zone 8).

Penelitian batugamping di Cekungan Limboto tepatnya di daerah Limboto Barat Kabupaten Gorontalo sangat menarik diteliti. Penyebaran batugamping di bagian tengah danau jelas menunjukkan kompleksitasi geologi daerah penelitian. Limboto Barat yang saat ini merupakan bagian dari danau air tawar jelas menarik diteliti mengingat keberadaan batugamping yang mengandung fosil foraminifera merupakan makluk hidup yang berasal dari laut. Untuk itu tujuan penelitian ini membuktikan sekaligus menganalisis lingkungan purba batugamping daerah Limboto Barat pada jutaan tahun lalu. Tujuan penelitian tersebut akan dicapai menggunakan dua metode yakni survei lapangan dan analisis laboratorium berupa analisis biostratigrafi. Berdasarkan hasil dan diskusi dari penelitian ini menunjukan bahwa terdapat tujuh spesies fosil foraminifera bentonik dengan lingkungan purbanya adalah brackish lagoons and estuaries. Kata-kata kunci: Batugamping, Limboto Barat, Lingkungan Purba PENDAHULUANKepulauan Indonesia secara geologis terletak di pusat dari pergerakan tiga lempeng aktif yakni Lempeng Eurasia, Lempeng Samudra Pasifik dan Lempeng Hindia-Australia [1]. Pengaruh pergerakan tiga lempeng membuat Pulau Sulawesi membentuk huruf K [1,2]. Bukti pengaruh tektonik pengangkatan di utara Cekungan Limboto yang saat ini tersingkap di permukaan dengan kecepatan pengangkatan 0,0699-0,0724 mm/tahun [3].Berdasarkan penelitian terakhir yang dilakukan terdapat beberapa jenis dan fasies pengendapan batugamping. Beberapa fasies batugamping yakni fasies coralline rudstone, perulangan mudstone-packstone, fasies, sandy micrite dan sandy allochem limestone [4,5,6,7].Penelitian ini sangat menarik untuk melengkapi penelitian sebelumnya mengenai batugamping dari segi komposisi fosil foraminifera. Penelitian mengenai paleobatimetri batugamping di selatan Danau Limboto pada zona neritik tengah-neritik luar [8,9].Umur batugamping di sekitar Danau Limboto berdasarkan penelitian terakhir yakni Miosen Akhir-Pliosen Awal [10] sedangkan penelitian sebelumnya berumur Pliosen-Pleistosen [11]. Perbedaan umur ini membuat penelitian terakhir mengusulkan nama formasi baru yakni Formasi Batugamping Limboto dari nama formasi sebelumnya yakni Formasi Batugamping Klastik [10,11].Keberadaan batugamping yang ada di bagian tengah Danau Limboto Kabupaten Gorontalo sangat menarik diteliti. Karena Limboto saat ini merupakan danau air tawar padahal batugamping yang terbentuk di sekitar Danau Limboto mencirikan lingkungan laut dengan keterdapatan melimpahkan pecahan koral di batugamping. Penelitian detail batugamping sangat menarik untuk mengetahui kondisi lingkungan purba jutaan tahun lalu. Mengacu latar belakang tersebut maka tujuan penelitian yang diangkat yakni menganalisis lingkungan purba batugamping daerah Limboto Barat Kabupaten Gorontalo. Analisis lingkungan purba akan memaksimalkan data kandungan fosil foraminifera di daerah penelitian. METODOLOGILokasi penelitian di Daerah Limboto Barat Kabupaten Gorontalo. Lokasi penelitian merupakan bagian utara Cekungan Limboto. Cekungan Limboto be...

The location of the study area is surging hills in Bongomene area, Gorontalo, Indonesia. In this study, a geological survey and sampling were taken, and then an analysis of the content of benthic foraminifera was performed in each sample. The study aims to discover the species of benthic foraminifera fossils and to determine the paleobathymetry to the studied regions. The results of the analysis contained seven fossils species, namely Ammomassilina alveoliniformis, Stelligerum astrononion, Haynesia germanica, Nonion fabum, Praeglobobulimina ovata, Rhabdammina discreata and Saccorhiza ramosa. Based on the content of benthic foraminifera fossils, paleobathymetry is determined as Middle Shelf to Outer Shelf in Bongomeme 1, while in Bongomeme 2 and 3 is Middle Shelf.

The limestone research within the Limboto Basin of Gorontalo Province becomes a new challenge, particularly for the study of planktonic foraminiferal biostratigraphy. This study uses the data obtained from the measured section in the north-western part of Limboto Lake. The purpose of this study is to determine the planktonic foraminiferal biozonation and the relative age of Limboto limestones. The analyzed planktonic foraminiferal fossils can be classified as well to moderately preserved of various species, in the context of abundance, categorized as frequent to abundant. There are three recognized planktonic foraminiferal biozones, i.e., two biozones for Miocene age (M13b and M14) and one biozone for Pliocene age (PL1). The Miocene biozones are named as Globorotalia plesiotumida partial range zone (M13b) and Pulleniatina primalis-Globoquadrina dehiscens concurrent range zone (M14), while the name of Pliocene biozone is Globorotalia acostaensis partial range zone (PL1). The results of this study can be a reference to propose an age of Limboto Limestone Formation. Identification and demarcation of the Limboto Limestone Formation are based on the time interval and relative age of the formation based on planktonic foraminifera.