Research Article |
Corresponding author: Meutia Farida ( meutia.farida@unhas.ac.id ) Academic editor: Florian Witzmann
© 2024 Meutia Farida, Asri Jaya, Asmita Ahmad, Jimmi Nugraha.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Farida M, Jaya A, Ahmad A, Nugraha J (2024) The Eocene to Oligocene boundary and paleoclimatic indications based on calcareous nannofossils of Tonasa Formation, South Sulawesi, Indonesia. Fossil Record 27(1): 221-231. https://doi.org/10.3897/fr.27.e96985
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The biostratigraphy of the Tonasa Formation in the Jeneponto Regency of South Sulawesi, Indonesia, is still poorly known, and there are barren ages, such as much of the Oligocene to Early Miocene. The Tonasa Formation is well exposed along the coast of the Jeneponto Regency, in which the Karama area consists of the most important outcrops of this formation which in this area consists of interbedded marl and limestone. Our study focuses on the biostratigraphy of the Karama area section A based on nannofossil. Samples were collected by measured stratigraphy methods and then subjected to investigation using smear slides. The assemblages of species were determined by semiquantitative analysis. Data analysis obtained three nannofossil datums (boundaries): The First Occurrence (FO) of Sphenolithus pseudoradians NP19/NP20), the First Occurrence of Sphenolithus distentus (CP.16/CP.17), and the Last Occurrence (LO) Sphenolithus predistentus (NP.23/NP.24. The zonal boundary was determined based on calcareous nannoplankton; the Late Eocene to Middle Oligocene boundary of the Tonasa Formation was found in this section. Interestingly, throughout this period, the marker species in this section is Sphenolithus. In addition, the presence of Sphenolithus, Discoaster, and Zygrhablithus bijugatus indicated that the basin was in warm water condition.
Calcareous nannoplankton, Carbonate platform, Nannofossil datum, Tonasa Formation, Warm water
Indonesia is located between three major plates: the Pacific Plate from the east, the Indo-Australia Plate moving to the north, and the Eurasia Plate, which is relatively passive. They have been actively moving, have caused complex geological conditions, and they have strongly influenced the geological history. One of the results of the collision of the three plates is the formation of Sulawesi Island with its unique K-shaped outline. The consequences of this geological condition are reflected in the stratigraphic setting that is found on Sulawesi Island.
The stratigraphic sequence of the southern arm of Sulawesi is from the Late Cretaceous to the present (
The age of the Tonasa Formation in Karama area is latest Eocene (P17) based on planktonicforaminifera (
One of the most important components of carbonate rock is nannofossils, which were primary producers. They are useful as a tool for determining the biostratigraphy, paleoceanography, and paleoclimate of marine sediments (
Carbonate rocks are widely distributed in the southern arm of Sulawesi (Fig.
Regionally, the Tonasa Formation is composed of partly layered and massive limestone, coral bioclastic, and calcarenite with Globigerina marl intercalation (
Stratigraphically, the southern part of Sulawesi is composed of rock formations from the Mesozoic to the Cenozoic. Tertiary-aged rocks are most widely distributed in this area. The Tertiary stratigraphy of the western part of South Sulawesi is divided into (1) the Tonasa Formation that was deposited interfingering with the Early Eocene Malawa Formation, and (2) the Camba Formation that was deposited above the Tonasa Formation during the Middle to Late Miocene. Carbonate development was terminated by the influx of volcaniclastic materials. In the eastern part of South Sulawesi, the Tonasa Formation interfingered with the middle part of the Salo Kalupang Formation around the Middle Eocene, and an unconformity was found at the upper part of the Tonasa Formation with respect to the younger rock formations (
A systematic calcareous nannofossil analysis was conducted starting from field data collection, sample preparation, and determination of the different species composing the assemblage. Samples were collected at each layer of the Karama A section by using measured stratigraphy methods at interbedded limestone and marl. A total of 23 layers were sampled and prepared using the smear slide method with a cover glass of 24 mm × 24 mm in size. Observation under a polarized microscope with 1000× magnification was carried out to recognize the species present in the assemblage (Bown 1999; Farida at al. 2019). The age was determined based on the First Occurrence (FO) and the Last Occurrence (LO) of marker species, following the standard zonation by
As a result of investigating the calcareous nannofossil content of the Tonasa Formation, 20 species were identified. These are Braarudosphaera bigelowii, Coccolithus pelagicus, Coccolithus sp., Cyclicargolithus abisectus, Cyclicargolithus floridanus, Dyctiococcites bisecta, Dyctiococcites scrippsae, Cyclicargolithus luminis, Reticulofenestra sp., Reticulofenestra hillae, Reticulofenestra spp., Discoaster deflandrei, Discoaster tanii, Discoaster sp., Sphenolithus moriformis, Sphenolithus distentus, Sphenolithus predistentus, Sphenolithus pseudoradians, Sphenolithus tribulosus, Zygrhablithus bijugatus. Fig.
Photomicrograph of nannofossils of the Karama A section with 1000× magnification: A. Braarudosphaera bigelowii. B, C. Coccolithus pelagicus. D. Coccolithus sp. E. Cyclicargolithus abisectus. F. Cyclicargolithus floridanus. G. Reticulofenestra bisecta. H. Dyctiococcites scrippsae. I. Cyclicargolithus luminis. J. Reticulofenestra sp. K. Reticulofenestra hillae. L. Reticulofenestra spp. M. Discoaster deflandrei. N, O. Discoaster tanii. P–R. Discoaster sp. S, T. Sphenolithus moriformis. U. Sphenolithus pseudoradians. V. Sphenolithus distentus. W. Sphenolithus predistentus. X. Sphenolithus tribulosus. Y. Zygrhablithus bijugatus.
Biozonation schemes were used to determine biostratigraphy of the Tonasa Formation in the Karama A section on the basis of calcareous nannofossils from the NP zonation of
Zonal boundary NP.19/NP.20
This zone is characterized by the FO of Sphenolithus pseudoradians (
Zonal boundary CP.16/CP.17
The next zonal boundary is CP16/CP17, which is marked by the FO of Sphenolithus distentus (
Zonal boundary NP23/NP24
This zonal boundary is based on the LO of Sphenolithus predistentus (
Calcareous nannofossils are known as a good tool to reconstruct paleoclimate, paleoenvironment, paleoceanography, or paleoecology. The presence of calcareous nannofossils that live in a typical climate indicates the climatic conditions when these rocks were deposited. For instance, Discoaster, Sphenolithus, and Zygrhablithus bijugatus, typically lived in warm water conditions. These species are present and almost abundant from the bottom to the top of the Karama A section, although their diversity declined and some species decreased in abundance.
As mentioned above, Discoaster is one of the typical species that lived in warm water. In the study area, Discoaster is observed almost all throughout the Karama A section, even though they are not abundant, and the numbers tended to decrease and finally disappeared (Fig.
A previous study investigated the biostratigraphy of the Tonasa Formation in the Karama area using planktonicforaminifera and identified a Late Eocene (
The calcareous nannoplankton shows a clear latitudinal distribution, related to the specified tolerance at different temperatures (
Some Discoaster and Sphenolithus are poorly preserved, which is why determining the species is difficult. Therefore, preservation has an effect on species quantification. Additionally, diagenetic processes such as overgrowth also make the identification of species impossible. The existence of Discoaster as a typical warm water species is important for the reconstruction of seawater temperature. However, it is not found in all layers and is not abundant. Therefore, we assume that the conditions of the studied area experienced a decrease in temperature, thus reducing the number of Discoaster individuals. Coccolithus pelagicus as typical cold-water species (
In this study, we identify three calcareous nannofossil datums, which are the FO of Sphenolithus pseudoradians (NP.19/NP.20), FO of Sphenolithus distentus (CP.16/CP.17), and LO Sphenolithus predistentus (NP.23/NP.24). The age of the Tonasa Formation in the Karama area (section A) is Late Eocene to Middle Oligocene. The diversity and number of specimens tend to decrease from the Eocene to the Oligocene but some increased again in the upper part of the Middle Oligocene, i.e. Discoaster, Sphenolitus, and Zygrhablithus, and the presence of these species indicate that the climate was under warm water to water cooling conditions through the Late Eocene to the Middle Oligocene.
M. F. initiated the research, conceptualized this study, and wrote the original manuscript. A.J., A.A., and J.N., are contributed to the discussion. All authors contributed to the writing of this paper.
We express our gratitude to the many parties who have helped conduct this study, the Research and Community Service Institution of Hasanuddin University for Penelitian Dasar UNHAS grant of Hasanuddin University in 2022, and to Akita University for the supporting equipment. We also thank the students who have participated in this study, either in the field or in the laboratory. Their hard work is highly appreciated. The authors also express their deepest gratitude to the Jeneponto Government for the research permit. Finally, we especially thank the anonymous reviewers for their comments to improve the quality of the manuscript.
Taxonomy of the nannofossil from The Tonasa Formation
Order COCCOSPHAERALES Haeckel, 1894
Family BRAARUDOSPHAERACEAE Deflandre, 1947
Genus Brarudospharea Deflandre, 1947
Braarudosphaera bigelowii, Deflandre, 1947
Layer: 1, 2, 3, 5, 6, 9, 10, 11, 12, 14, 16, 22, 23.
Order COCCOLITHALES Schwarz, 1932
Family COCCOLITHACEAE Poche, 1913
Genus Coccolithus Schwarz, 1954
Coccolithus pelagicus (Wallich) Schiller, 1930, Layer: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23.
Coccolithus sp., Layer 3, 4, 5, 6, 7, 8, 9, 10, 11, 19, 20, 21, 22.
Order DISCOASTERALES Hay, 1977
Family DISCOASTERACEAE Tan, 1927
Genus Discoaster Tan, 1927
Discoaster deflandrei Bramlette & Riedel, 1954, Layer: 1, 2, 3, 4, 9, 10, 11, 12, 14, 15, 16, 18, 19, 20, 21, 22, 23.
Discoaster sp. Layer: 3, 4, 9, 11, 12, 13, 14, 15, 18, 19, 20, 21, 22.
Discoaster tanii Bramlette & Riedel, 1954, Layer: 3, 6, 7, 12, 14, 15.
Family SPHENOLITHACEAE Deflandre, 1952
Genus Sphenolithus Deflandre, 1952
Sphenolithus moriformis Bramlette & Wilcoxon, Layer: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23.
Sphenolithus distentus (Martini, 1965) Bramlette & Wilcoxon, 1967, Layer: 12, 14, 16, 18, 21.
Sphenolithus predistentus Bramlette & Wilcoxon, 1967, Layer: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.
Sphenolithus pseudoradians Bramlette & Wilcoxon, 1967, Layer: 3, 4, 14, 15.
Sphenolithus tribulosus Roth, 1970, Layer: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.
Order ISOCHRYSIDALES Pascher, 1910
Family NOELAERHABDACEAE Jerkovic, 1970 emend. Young & Bown, 1997
Genus Reticulofenestra Hay, Mohler & Wade, 1966
Cyclicargolithus abisectus Wise, 1973, Layer:18, 19, 20, 21, 22, 23.
Cyclicargolithus floridanus Bukry, Layer: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23.
Cyclicargolithus luminis Bukry, Layer: 2, 3, 5, 6, 7, 8, 10, 11.
Reticulofenestra hillae Bukry & Percival, 1971, Layer: 4, 5, 6, 7, 10, 12, 13, 14,
Reticulofenestra sp. Layer: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23.
Reticulofenestra spp. Layer: 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23.
Reticulofenestra bisecta (Hay, Mohler & Wade, 1966) Roth, 1970, Layer: 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23.
Order COCCOLITHOPHYCEAE ORDO INCERTAE SEDIS Baky, 1988.
Genus Dictyococcites Black, 1967
Dictyococcites scrippsae Bukry & Percival, 1971, Layer: 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23.
Holococcoliths sensu Young et al., 2003
Genus Zygrhablithus Deflandre, 1959
Zygrhablithus bijugatus Deflandre, 1959, Layer: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23