KETERKAITAN PERUBAHAN IKLIM PADA GLASIAL AKHIR - HOLOSEN TERHADAP TINGKAT KEANEKARAGAMAN FORAMINIFERA DI LAUT HALMAHERA

Fitria Ratna Pratiwi, Suwarno Hadisusanto, Luli Gustiantini, Nazar Nurdin, Mira Yosi

Abstract


Laut Halmahera terletak pada Western Pacific Warm Pool (WPWP), yaitu pusat konveksi panas di Samudera Pasifik Barat tropis. Laut ini merupakan salah satu jalur masuk Arlindo yang menghubungkan massa air Samudera Pasifik dengan Samudera Hindia. Sehingga area ini penting untuk rekonstruksi paleoklimat. Peristiwa perubahan glasial akhir-interglasial (Holosen) merupakan peristiwa di masa lalu yang sangat mempengaruhi kondisi Laut Halmahera. Salah satu proksi yang dapat digunakan untuk mencatat perubahan iklim di masa lalu adalah sisa-sisa makhluk hidup, termasuk foraminifera. Perubahan yang terjadi pada foraminifera dapat diamati dari tingkat  keanekaragaman, kemelimpahan, dominansi, dan keseragaman. Penelitian dilakukan dengan menggunakan sampel sedimen bor MD10-3339, yang diambil di Laut Halmahera (00o26,67’LS dan 128o50,33’BT) pada kedalaman 1.919 m, dalam survei MONOCIR 2 tahun 2010. Sampel yang digunakan pada rentang 20 cm hingga 1.930 cm dengan interval 60 cm pada tiap sampel, yang dianggap mewakili waktu terjadinya glasial-interglasial. 30 sampel kemudian diamati dan dilakukan analisis secara kuantitatif. Teridentifikasi 52 spesies yang terdiri dari 32 spesies foraminifera bentonik dan 21 spesies foraminifera planktonik. Nilai indeks keanekaragaman, nilai indeks keseragaman, dan indeks dominansi menunjukkan nilai yang fluktuatif sejak glasial-interglasial, dengan nilai rata-rata 1,66; 0,35; dan 0,3. Walaupun tidak menunjukkan pola glasial-interglasial, namun pada sekitar umur 12.519 BP, nilai indeks keanekaragaman dan nilai keseragaman menunjukkan nilai yang lebih rendah dibandingkan dengan nilai yang lain yaitu 1,102 dan 0,26. Sebaliknya, indeks dominansi mencapai nilai tertinggi yaitu 0,55.  Selain itu, persentase P. obliqueloculata pada umur ini menjadi sangat dominan yaitu 73,05%. Hal tersebut kemungkinan berkaitan dengan peristiwa Younger Dryas.

Kata Kunci : Foraminifera, Younger Dryas, Laut Halmahera.


Halmahera Sea lies in the centre of Western Pacific Warm Pool (WPWP), the warmest area in Tropical Pacific Ocean that play a role as center of heat convection. It is also one of the Indonesian throughflow pathways connecting water mass from Pacific Ocean to The Indian Ocean, therefore this area is considered important for climatic reconstruction. Glacial-interglacial cycle is one of the major events in the past that strongly influence the Halmahera Sea. Potential proxies for paleoclimatic reconstruction are including living organisms remain, such as foraminifera. Respond of foraminifera can be observed from their diversity, abundance, dominance, and their evenness. This study was conducted by analizing sediment core MD10-3339, collected from the Halmahera Sea (00o26.67” S, 128o50.33” E) in 1,919 m water depth, during the cruise MONOCIR 2 in 2010. Samples were analized from 20 cm to 1,930 cm at 60 cm intervals. A total of 30 samples were observed and analyzed. 52 species of foraminifera are found, composed of 32 species of benthonic foraminifera and 21 species of planktonic foraminifera. The analyses of diversity index, evenness, and dominance indicate fluctuated values between glacial-interglacial, with averages values are 1.66, 0.35, and 0.3 respectively. Although the values do not indicate glacial-interglacial trend, however, in 12,519 BP diversity index and evenness index showed the lowest number compared to the other ages (1.102 and 0.26, respectively),in contrast the highest dominance index (0.55). Furthermore, at this time, the percentage of Pulleniatina obliquiloculataincrease (73.05%) and become dominant. This occurrence might be related to the Younger Dryas event.

Keywords: Foraminifera, Younger Dryas, Halmahera Sea.


Keywords


Foraminifera; Younger Dryas; Laut Halmahera

Full Text:

PDF

References


Baohua, L., J. Zhimin, and W. Pinxian. 1997. Pulleniatina obliquiloculata as a paleoceanographic indicator in the southern Okinawa trough during the last 20.000 years. Marine Micropaleontology 32:59-69.

Bernhard, J.M. and B.K. Sen Gupta. 1999. Foraminifera of oxygen-depleted environments. Modern Foraminifera 1 : 201-216.

Bolli, H.M., J.B. Saunders and K. Perch-Nelson. 1985. Plankton Stratigraphy. Cambridge University Press. Cambridge.

Boltovskoy, E. and R. Wright. 1976. Recent Foraminifera. Dr. W. June, B. V. Publisher. p: 515.

Buzas, M. A. Dan T.G. Gibson. 1969. Species diversity: benthonic foraminifera in Western North Atlantic. Science 163(3862) : 72–75.

Carlson, A.E. 2010. What caused the Younger Dryas Cold Event?. Geology 38(4) : 383-384.

Ding, X., F. Bassinot, F. Guichard, Q.Y. Li, N.Q. Fang, L. Labeyrie, R.C. Xin, M.K. Adisaputra, and K. Hardjawidjaksana. 2006. Distribution and ecology of planktonic foraminifera from the seas around the Indonesian Archipelago. Marine Micropaleontology 58 : 114-134.

Funnel, B.M. and W.R. Riedel (ed). 1971. The Micropaleontology of Oceans. Cambridge University Press. Cambridge.

Gustiantini, L., K.A. Maryunani, R. Zuraida, C. Kissel, F. Bassinot, dan Y. Zaim. 2015. Distribusi foraminifera di Laut Halmahera dari glasial akhir sampai resen. Jurnal Geologi Kelautan 13(1) : 25-36.

Gustiantini, L. 2018. Paleoclimate reconstructions by multiproxy approaches in the Halmahera Sea since the Late Pleistocene – Holocene (Disertation). ITB. Bandung.

Haq, B.U. and A. Boersma (ed). 1983. Introduction to Marine Micropaleontology. Elsevier Biomedical. New York.

Hayward, W.B. 2004. Foraminifera-based estimates of paleobathymetry using modern analogue technique, and the subsidence history of the early Miocene Waitemata Basin. New Zealand Journal of Geology & Geophysics 47 : 749- 767.

Herho, S.H.S. 2017. Paleoklimatologi untuk Pemula. Perkumpulan Studi Ilmu Kemasyarakatan ITB. Bandung.

Holbourn, A.E. and A.S. Henderson. 2002. Re-Illustration and Revised Taxonomy for Selected Deep-Sea Benthic Foraminifers. Paleontologica Electronica.

Jones, D.K. 1969. Introduction to Microfossils. Hefner Publishing Company. New York.

Jones, R.W. 2014. Foraminifera and Their Applications. Cambridge University Press. Cambridge.

Krebs, C.J. 1989. Ecologycal Methodology. Harper & Row Inc. Publisher. New York.

Linsley, B.K. 1990. The record of deglaciation in the Sulu Sea : evidence for the younger dryas event in the tropical western pacific. Paleoceanography 5(6):1.025-1.039.

Loeblich, A.R. and H. Tappan. 1988. Foraminiferal Genera and Their Classification. Van Nostrand Reinhold. New York.

Ludwig, J.A. and J.F. Reynolds. 1988. Statistical Ecology : A Primer Methods and Computing. John Wiley dan Sons. New York.

Murray, J. W. 1976. A method of determining proximity of marginal seas to an ocean. M. Geol. 22 : 103-119.

Postuma, J.A. 1971. Manual of Planltonik Foraminifera. Elsevier Publidhing Co. London.

Thirumalai, T., J.N. Richey, T.M. Quinn, and R.Z. Poore. 2014. Globigerinoides ruber morphotypes in the Gult of Mexico : a test of null hypothesis. Scientific report 4 (6018) : 1-7.

Todd, R. 1994. Planktonic Foraminifera from Deep-Sea Cores off Eniwetok Atoll. United States Government Printing Office. Washington.

Valchev, B. 2003. On the potential of small benthic foraminifera as paleoecological indicators: recent advances. Annual University of Mining and Geology “St. Ivan Rilski” 46 (1) : 189-194.

van Marle, L.J. 1988. Bathymetric distribution of benthic foraminifera on the Australian-Irian Jaya continental margin, Eastern Indonesia. Marine Micropaleontology 13 : 97-152.

Xu, J., W. Kuhnt, A. Holbourn, M. Regenberg, and N. Andersen. 2010. Indo-Pacific Warm Pool variability during the Holocene and Last Glacial Maximum. Paleoceanography 25 : 1-16.




DOI: http://dx.doi.org/10.32693/jgk.18.1.2020.635