Stiva Cave: a New Discover of Prehistoric Hominid Underwater Cave

Stiva Cave is an underwater cave (15,3 m below recent sea level), which located in Nusa Penida, Bali, Indonesia. Nusa Penida is a Karst landscape island in southern Bali Island. No many underwater caves are known and explored in this area, Stiva Cave is a first underwater cave which explored and discovered in Nusa Penida area. In this cave we found a number of fossils that we identified as vertebrate fossil and unique process that very potential for geotourism, especially for fun diving tourism. We mapped entire cave tunnel and measure a safety and risk for scuba diving, then we identified the fossil. At the result, there a several risk that need to be aware and several safety procedures that must be allow for observer. In other way, we found many similar fossils that and it spread in different tunnel that very potential for education in geotourism. We suggest that this cave is a shelter for hominid species when Last Glacial Maximum happens, before 21.000 years ago


Int r oduct i on
Nusa Penida located in southern Bali, mostly underground river system w hich has connection to other river system. Based on its genesis, Karst in Nusa Penida has three sequences w hich can derived based on its characteristics in lithology. In several discussions, this ecosystem start at M iocene (23,5 millon years ago). Until today, sedimentation of carbonate in this system still produce, almost in shoreline in Nusa Penida (P.H. Barber, 2000).
Stiva cave is an underw ater cave in Nusa Penida, Bali, Indonesia. It is has been found in 2016 by local diver. This cave located in below recent mean sea levels. Stiva cave is one attractive site for tourism in Toyapakeuh, Nusa Penida (N:-8.685659, W:115.479822), see Fig. 1. But until w e start to explore this cave, no one realized that there are several fossil w hich deposited in this cave because t hese fossil covered by sediment. So in this research w e aim to discover all the cave tunnels, fossil that deposited, and reconstructing how these fossil deposited in this cave. This research hopefully gave advice for guiding diver in moment entered the cave Fi g 1. Location of Stiva Cave, Toyapakeuh,Nusa Penida, Bali, Indonesia.

M et hod
Cave M appi ng. There are three parts mapping sections, this procedure necessary to do because w e need to calculated the oxygen tank, because it is our limitation w hen mapping in underw ater cave and it in dark condition (see Fig. 2). We measured the w idth and height in every part cave tunnels for sketching its tunnel morphology. In every section, w e collect ed sediment sam ple using tube coring, completed w ith thick of the sediment for further analysis. W e also collected several fossils for identification and reconstructing the paleoenvironment of this cave.
Fi g. 2. Stiva Cave condition, w e need plan more comprehensive for underw ater mapping Sedi m ent Analysi s. This procedure necessary to do. We can identify how this cave submerge at few step based their sediment characteristic. We classify sediment based their size (sand, silt, and clay) by its percentage.

Result
Stiva cave enterance at 15,3 m below mean sea level. It is heading to northeast and has height 280 cm and w idth 510 c has tw o branches heading t o east ( ) and south ( ). The Cave tunnel has 179 m, south tunnel is the longest tunnel in this system, 37,5 m and the other is 25,8 m. We can find several cham ber in along tunnel (see Fig. 3 The thickness of sediment layer from mouth to edge is gradually thinny and smoothy. Percentation of clay increase gradually into deep cave, follow by decreasing percentation of sand and silt. We can found several cham ber in each tunnel branch. The east tunnel/right -hand branch tunnel/left -E) has 2 cham ber too (see Fig. 3 and Fig. 4).
We also found several vertebrate, its looks accumulated in cham bers. There are Proboscidea mandibular that can be found in front cham ber, the sarchum of Turtoise in 1 st cham ber I right hand branch, t hen the fem ur and vertebrate of Cervidae in 2 nd cham ber. In left -hand branch w e also can found more Cervidae fossil and Probocidea Scapula, accumulated in 3 rd and 4 th cham ber (see Fig. 5).

Di scussi on
Stiva cave form from sub-surface hydrology system of karst landscape. The freshw ater from the rain penetrated into body of carbonate rock to crack and w eak rock then eroded and made it into a cave tunnel. W hen the carbonate rocks exposed into atmosphere, it w ill react w ith the air and the acid from rain. When t his cave form it w ill make tunnel bigger and bigger in time. But it very fragile and has potential to break if the tunnel This cave is big enough to entered by dw arf humanoid, but very difficult to enter by scuba. It needs special technique to access safely. Based on location of fossil in that cave, it has potential that in past time this cave is a prehistoric hominid cave. We predict, in the past time, this cave is a shelt er for cavern hominid. There are a group of hominid carrying the hunt ed pray into their shelt er, share, and eat them together. They share it to each other then, left the bone into cave floor. When the cave abounded, the bone deposited in this cave until the cave submerge, and gradually change into fossils.
Fi g. 6. the sea level change graphic began in Pleistocene (21.000 years ago) to recent mean sea level.
We suggest that t his cave is a terrestrial cavern system, specially at the end of Pleistocene, around 21.000 years ago, the sea level is -114 m below recent sea level (see Fig. 6), it know n as Last Glacial M aximum (Liu, J. P., & M illiman, J. D. 2004;Tjia, H. D. 1992;Tjia, H. 2014) In this condition, Stiva Cave still exposed to the atm osphere and can be access by t errestrial fauna include t he hominid (Fairbanks, 1989;Hanebut h, et al, 2000;Solihuddin, 2014). Cave in karst ecosystem is the best for hominid shelter, it w ill cool in heat atm osphere condition, and it w ill w arm if in cold condition. Karst can maintain the temperature more stable in fluctuative environment temperature. It must be good t o be shelter. After the Pleistocene ending, the global temperature is rising faster and make the ice in earth polar melting faster (Abdussam atov, 2011;Geyh, et al, 1979;Sathiam urthy and Voris, 2006). The implication of that, sea level rising faster and reach into recent sea level. When sea level rising, Stiva Cave w ill drow n by sea w ater and left the bone in that cave and fossilized, it can explain w hy in that cave w e can found fossil so many in specific type and accumulated in specific location in cave. The sediment in this cave can explain how sedimentation happen in t hat time. In front of cave w e can found more course sediment correlated in more deep tunnel. The beach sand can enter t he cave, but it more hard to enter , if sea more deep. This cave has geological value, especially in paleontology.

Conclusi on
Stiva Cave is one of underw ater cave that has rich vertebrate fossil. The fossil preserved w ell in cave condition, w hich expels from the sunlight and covered by sediment w hich has small grain. We suggest t hat the rich fossil in this cave is a result of prehistoric hominid activity, that carry they hunt ed and eat t hem in this cave. This cave must be exposed to the atm osphere at t hat time, w hen global mean sea level still far below compared w ith recent. It could be happened w hen last glacial maximum happens, 21.000 years ago. Then t his cave abounded by them, w hen t his cave close enough w ith shore or frequent ly flooded at high tides.