Graduate School and Faculty of Science

Paleontologists typically treat major episodes of extinction as single and distinct events in which a major environmental perturbation results in a synchronous evolutionary response. Alternatively, the causes of biotic change may be multifaceted and extinction may lag behind the changes ultimately responsible because of nonlinear ecological dynamics. We examined these alternatives for the major episode of Caribbean extinction 2 million years ago (Ma). Isolation of the Caribbean from the Eastern Pacific by uplift of the Panamanian Isthmus was associated with synchronous changes in Caribbean near shore environments and community composition between 4.25 and 3.45 Ma. Seasonal fluctuations in Caribbean seawater temperature decreased 3-fold, carbonate deposition increased, and there was a striking, albeit patchy, shift in dominance of benthic ecosystems from heterotrophic mollusks to mixotrophic reef corals and calcareous algae. All of these changes correspond well with a simple model of decreased upwelling and collapse in planktonic productivity associated with the final stages of the closure of the isthmian barrier. However, extinction rates of mollusks and corals did not increase until 3-2 Ma and sharply peaked between 2 and 1 Ma, even though extinction overwhelmingly affected taxa commonly associated with high productivity. This time lag suggests that something other than environmental change per se was involved in extinction that does not occur as a single event. Understanding cause and effect will require more taxonomically refined analysis of the changing abundance and distribution patterns of different ecological guilds in the 2 million years leading up to the relatively sudden peak in extinction.

The marine environment is an abundant source of diverse biologically active compounds that demonstrate great potential applications in pharmaceutics and medicine. Although novel biologically active secondary metabolites can be potentially found in bryozoans, there have been a few studies on these organisms. Bryozoans are sessile colonial animals commonly found in great diversity in shallow waters. In this study, samples of the bryozoan Cryptosula zavjalovensis Kubanin were collected from Akkeshi, Japan, and were extracted using ethanol. The crude extract was separated using ethyl acetate (EtOAc) and water to obtain organic and aqueous fractions, respectively. In the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the EtOAc fraction demonstrated cytotoxicity towards MCF7 breast cancer cells. The EtOAc extract was subsequently fractionated through solid-phase extraction using a gradient of methanol and water (E1 80:20 v/v and E2 100:0 v/v) and using methanol and chloroform (E3 50:50 v/v). Toxicity profiling revealed that the toxicity toward the human MCF7 breast cancer cells of the E2 and E3 fractions is comparable to that of cisplatin, indicating the excellent cytotoxic activity of the EtOAc fractions of C. zavjalovensis. Further studies are thus warranted to isolate the novel compounds in these fractions and determine their potential chemotherapeutic application.

The 2011 Tohoku-oki tsunami caused severe damage to the coastal regions of eastern Japan and left a sediment veneer over affected areas. We discuss differences in depositional characteristics of the 2011 Tohokuoki tsunami from the viewpoint of the sediment source, coastal topography and flow height. The study area on the Misawa coast, northern Tohoku, includes a 20 km long coastline with sandy beaches, coastal dunes and a gently sloping lowland. This landscape assemblage provides an opportunity to examine the effects of topography on the characteristics of the tsunami deposit. During field surveys conducted from April 10 to May 2, 2011, we described the thickness, facies, and structure of the tsunami deposit. We also collected sand samples at approximately 20 m intervals along 13 shore-perpendicular transects extending up to 550 m inland, for grain size and mineral assemblage analysis. The tsunami flow height was estimated by measuring the elevation of debris found in trees, broken tree limbs, or water marks on buildings. The nature of the coastal lowland affected the flow height and inundation distance. In the southern part of the study area, where there is a narrow, 100 m wide low-lying coastal strip, the run-up height reached 10 m on the landward terrace slopes. To the north, the maximum inundation reached 550 m with a run-up height of 3.2 m on the wider, low-lying coastal topography. The average flow height was 4-5 m. The tsunami eroded coastal dunes and formed small scarps along the coast. Immediately landward of the coastal dunes the tsunami deposit was more than 20 cm thick, but thinned markedly inland from this point. Close to the dunes the deposit was composed largely of medium sand (1-2 Φ) with planar and parallel bedding, but with no apparent upward fining or coarsening. The grain size was similar to that of the coastal dune and we infer that the dunes were the local source material for the tsunami deposit at this point. The mineral assemblage of the tsunami deposit was dominated by orthopyroxene and clinopyroxene and was also similar to the dune and beach sand. At sites more than half the inundation distance inland, the thinner tsunami deposit consisted mainly of fine sand (2.375 Φ) with some upward fining. The difference in grain size and sedimentary characteristics was probably caused by differences in sediment transportation and depositional processes. We infer that the well-sorted, finer sediments were deposited out of suspension, whereas the relatively coarse sands were laid down from traction flows. The depositional characteristics of the 2011 Tohoku-oki tsunami deposit appeared to have been affected mainly by the coastal topography and the extent of erosion at any one point, as opposed to flow height.

The 2010 Mentawai earthquake (magnitude 7.7) generated a destructive tsunami that caused more than 500 casualties in the Mentawai Islands, west of Sumatra, Indonesia. Seismological analyses indicate that this earthquake was an unusual ''tsunami earthquake,'' which produces much larger tsunamis than expected from the seismic magnitude. We carried out a field survey to measure tsunami heights and inundation distances, an inversion of tsunami waveforms to estimate the slip distribution on the fault, and inundation modeling to compare the measured and simulated tsunami heights. The measured tsunami heights at eight locations on the west coasts of North and South Pagai Island ranged from 2.5 to 9.3 m, but were mostly in the 4-7 m range. At three villages, the tsunami inundation extended more than 300 m. Interviews of local residents indicated that the earthquake ground shaking was less intense than during previous large earthquakes and did not cause any damage. Inversion of tsunami waveforms recorded at nine coastal tide gauges, a nearby GPS buoy, and a DART station indicated a large slip (maximum 6.1 m) on a shallower part of the fault near the trench axis, a distribution similar to other tsunami earthquakes. The total seismic moment estimated from tsunami waveform inversion was 1.0 9 10 21 Nm, which corresponded to M w 7.9. Computed coastal tsunami heights from this tsunami source model using linear equations are similar to the measured tsunami heights. The inundation heights computed by using detailed bathymetry and topography data and nonlinear equations including inundation were smaller than the measured ones. This may have been partly due to the limited resolution and accuracy of publically available bathymetry and topography data. One-dimensional run-up computations using our surveyed topography profiles showed that the computed heights were roughly similar to the measured ones.

The research was carried out on the sediments of the Batuasih Formation cropping out at Batuasih Village, Cibatu River, Padaarang Sukabumi. Data obtained from field observation, as well as foraminifera and sedimentology analyses conducted in the laboratory, were used to interpret its depositional environment. The investigation was focused on planktonic and benthic foraminiferal assemblages for depositional environment interpretation that might not be used by previous researchers. The Batuasih Formation is composed of black shaly claystone, where the lower part is rich in clay ball, and limestone intercalations in the upper part of the formation. In Cibatu Section, no clay balls is recognized in the lower part, but intercalations of limestone still occur. However, a contrast difference is found in Padaarang section, where green claystone interbeds with fine-grained sandstone. The Batuasih Formation conformably overlies the Walat Formation containing conglomerate. Foraminifera fossil found in the Batuasih Formation consists of bad preserved black benthic and planktonic foraminifera, more abundant towards the lower part of formation. Based on foraminifera assemblage comprising genus Uvigerina, Cibicides, Elphidium, Operculina, Bulimina, Bolivina, Eponides, and Neoconorbina, supported by sedimentology data, the Batuasih Formation was deposited in a shallow to deep marine environtment, during Early Oligocene (P19) time. Upwards to be the Rajamandala Formation, the depositional environment tends to be shallower gradually.

This paper focuses on the Quaternary Baturetno Formation. An earlier research concluded that the black
clay of the Baturetno Formation formed as a ‘palaeolake’ deposit. The ‘palaeolake’ was interpreted to form due to
the shifting course of the Bengawan Solo Purba River in relation to Pliocene tectonic tilting in the southern Java.
The stratigraphy of the Baturetno Formation was observed in the western part of the Baturetno Basin, and based on
marker beds, the Baturetno Formation was classified into three units: (1) Gravel unit (GR) in the upper part, (2) clay
unit (CU) in the middle part, and (3) sand-gravel unit (SG) in the lower part. There are floating gravel fragments of
andesite, claystone, coral, and limestone with diameters of up to 10 cm in the clay unit. The particle size of sediment
reflects the environment, but the lake deposition occurs under very quiet conditions. The occurrence of these
fragments within the clay cannot be explained if the clay was deposited within a lake environment. The occurrence
of floating fragments in the black clay of Baturetno Formation can best be explained through mudflow process. The
cohesive strength of the mudflow is responsible for the ability of large fragments to float within the mud matrix. In
general, the Baturetno Formation is inferred to be an alluvial fan deposit. The presence of sand, gravel, and mud are
characteristics of alluvial fan deposits.

Expanding knowledge of facies variation in tsunami deposit is meaningful not to overlook tsunami traces in sedimentary records and then to reconstruct more precise tsunami history. In general, it is assumed that tsunami deposits are coarser than background sediments because of its sedimentation under higher energy condition. Hunting for paleotsunami deposit actually tends to focus on sand layers in muddy

Penelitian yang dilakukan pada percontoh singkapan batulempung Formasi Batuasih di daerah Suka bumi bertujuan untuk mengetahui potensi batuan sumber hidrokarbon dan karakteristiknya. Formasi Batuasih yang terendapkan secara selaras di atas Formasi Walat, secara litologi tersusun oleh batulempung berwarna abu-abu kehitaman, menyerpih, brittle, mengandung clay ball, urat-urat kalsit, dengan sisipan batugamping. Hasil analisis geokimia terhadap dua belas percontoh batulempung menunjukkan nilai TOC sebesar 0,49-1,14 % .T maks empat percontoh yang mempunyai kisaran 431-434 o C menunjukkan tingkat kematangan termal yang belum matang, sedangkan delapan percontoh lainnya masuk kategori sudah matang (436-441 o C). Nilai HI berkisar dari 77-191 mg HC/TOC, dan berada dalam fasies C dan CD. Dari hasil tersebut terlihat bahwa batuan induk di daerah penelitian dapat menghasilkan minyak dan gas dalam kuantitas kecil. Potensi hidrokarbon di daerah penelitian menunjukkan kategori kekayaan material organik rendah hingga menengah, dengan kerogen yang termasuk ke dalam tipe II dan III. Kualitas batuan sumber percontoh berdasarkan nilai HI termasuk dalam kategori gas prone.

Cekungan di antara busur yang berada di dalam lingkungan zona cekungan laut dalam busur belakang atau zona kompresi Majalengka-Banyumas terbentuk akibat peregangan pasangan patahan geser Gabon dan Pamanukan-Karangbolong yang berarah baratlaut-tenggara pada Miosen Awal. Salah satu sub-cekungan tersebut adalah Sub cekungan Majenang tempat diendapkan sedimen volkanoklastik berupa endapan arus gravitasi epiklastik dalam suatu kipas bawah laut berumur Miosen Akhir-Pliosen. Endapan tersebut berasal dari batuan yang berasosiasi dengan volkanik busur belakang bersifat kalk alkalin yang tumbuh di dalam zona patahan tersebut atau memisahkan sub-sub cekungan dan sumber lain berasal dari Pegunungan Selatan. Pasangan patahan geser Gabon dan Pamanukan-Karangbolong menjadi tidak aktif setelah berkembangnya patahan regional Bogor-Bandung-Majalengka berarah barat-timur akibat penunjaman normal Lempeng Australia. Studi rinci pola struktur geologi, anomali gayaberat dan kinematika struktur geologi yang berkembang di Zona Majalengka-Banyumas, proses sedimentasi dan stratigrafi endapan arus gravitasi kipas bawah laut, serta hasil analisis petrologi dan kimia batuan piroklastik dan epiklastik di dalam zona ini memberikan bukti kuat terbentuknya suatu sub-sub cekungan di antara busur di wilayah cekungan laut dalam busur belakang pada saat Miosen Akhir di bagian barat Pulau Jawa.

ABSTRAK Lokasi penelitian terletak di sebelah selatan Kota Tarahan, Lampung merupakan daerah yang terkena dampak gelombang tsunami letusan Gunung Krakatau 1883. Penelitian ini dilakukan untuk mengetahui karakteristik endapan tsunami Krakatau 1883 dengan mengamati profil stratigrafi pada dinding sungai dan parit uji pada 12 lokasi di 3 (tiga) transek. Analisis laboratorium meliputi analisis besar butir, mikrofauna (foraminifera dan moluska) dan mineral berat. Endapan tsunami yang teridentifikasi berupa lapisan pasir dengan pecahan cangkang dan fragmen karang. Lapisan pasir ini berasosiasi dengan lapisan abu vulkanik dan lapisan batuapung yang merupakan material hasil letusan Krakatau 1883. Kandungan foraminifera bentik dan moluska memperlihatkan bahwa gelombang tsunami menggerus dasar laut hingga kedalaman 30-40 m. Berdasarkan pengamatan singkapan dan analisis besar butir, terdapat empat pola perulangan struktur penghalusan besar butir ke arah atas dalam satu lapisan endapan tsunami. Hal itu menunjukkan bahwa kemungkinan ada empat gelombang tsunami yang terjadi pada saat itu. Hasil analisis mineral berat cenderung memperlihatkan pola perubahan komposisi ke arah atas mengikuti perubahan besar butir.