Friday, June 6, 2008

Javanese Hominid Sites

1. Sangiran

The Sangiran area has yielded a number of human fossil bones of Pithecanthropus and Meganthropus. To clarify the stratigraphic horizons of these human fossil-bearing beds, the Indonesia-Japan Joint research team spent about 170 days, between 1976 and 1979, in surveying the area. As a result, the team was able to subdivide the Kalibeng, Pucangan, Kabuh and Notopuro Formations by means of pyroclastic markers, and to reveal the complicated geological structure of the Sangiran Dome.

Geologic Setting and Previous Investigation

The Sangiran area is a hilly area around the Sangiran village located about 10 km north of Surakarta (Solo). Its maximum altitude is 183 m, and structural dome trending NNE-SSW occupies its central part. This structure which is called the Sangiran Dome is approximately 8 km long and 4 km wide. It has been dissected by tributaries of the Solo River, namely the Cemoro, Brangkal, Pohjajar Rivers and many smaller streams. Consequently, the strata around the dome are well exposed.
Van Es (1931) who first published a geological map of the Sangiran area, 1:20,000 in scale, divided its strata in ascending order into: a) Bluish gray (marine) clay, b) Turritella beds (argilaceous sand), c) Balanus limestone, d) Corbicula beds, e) Volcanic breccia, f) Black (freshwater) clay with intercalations of g (Diatom beds), h (Tuffaceous layer), and i (Yellow marine clay), k) Lower conglomerate-tuff series, and l) Upper conglomerate-boulder breccia-tuff series. He recognized unconformable relationship between b and c, c and d, and f and k, and assigned a-b to the lower Pliocene, c to the middle Pliocene, d-f to the upper Pliocene and k-l to the Pleistocene.
Von Koenigswald (1940) who published a geological map of the Sangiran area on the same scale as that of van Es (1931), subdivided the strata into the Upper Kalibeng beds (marine sand and clay, Balanus limestone and Corbicula beds), the Pucangan beds (lower volcanic breccia, black freshwater clay with marine intercalation), the Kabuh beds (Grenzbank, lower conglomerate and tuff), and the Notopuro beds (upper volcanic breccia, upper conglomerate and tuff) in ascending order. He found erosional hiatuses between the Upper Kalibeng and the Pucangan beds and between the Kabuh and Notopuro beds. He estimated the total thickness of these strata at about 350 m. The subdivisions by von Koenigswald are based on Duyfjes lithostratigrapic units (1936), the type localities of which were established in the eastern part of the Kendeng Hills, 100 to 180 km east of the Sangiran area. In this type area, Duyfjes (1936 and 1938a-d) assigned the Kalibeng Formation, the Pucangan Formation and the Kabuh-Notopuro Formations to be Pliocene, lower Pleistocene and middle Pleistocene respectively. Von Koenigswald (1940) regarded the Pucangan beds containing Jetis fauna as early Pleistocene age, and the Kabuh beds containing Trinil fauna as middle Pleistocene age, on the basis of his vertebrate stratigraphy in Central and East Java. The overlying Notopuro beds in Central and East Java were assigned by van Bemmelen (1949) to the upper middle and lower upper Pleistocene.
Sartono (1961, 1970 and 1975) who published geological maps of the Sangiran area divided the strata, in ascending order, into the Upper Kalibeng beds (marine clays and marls, marine sand with Turritella, Balanus limestone, and Corbicula beds), the Pucangan beds (volcanic breccia and black limnic clay with marine intercalations), the Kabuh beds (sandstone and volcanic tuff, and lower conglomerate) and the Notopuro beds (upper conglomerate and volcanic layers). He assigned the Upper Kalibeng beds to the upper Pliocene, the Pucangan beds to the lower Pleistocene and the Kabuh and Notopuro beds to the middle Pleistocene. In a recent paper which contains a geological map of the central part of the Sangiran area, Sartono (1978) changed the "beds" into "Formation".

Stratigraphy of Late Cenozoic Strata

Since the late Cenozoic strata of the Kendeng Hills between Surabaya and Trinil were subdivided into the Kalibeng, Pucangan, Kabuh and Notopuro Formations by Duyfjes (1936), these lithostratigraphic units have been widely used for the subdivisions of human fossil-bearing formations west of Trinil. In the course of our survey in the Sangiran area, well exposed sections, however, were chosen as the standard for each formation in the area. While the formation names by Duyfjes were used for convenience during the field survey. Furthermore, the aggregation of the above mentioned units can be named the Kendeng Group.
The late Cenozoic strata of the Sangiran area are subdevided, in ascending order, into the Kalibeng, Pucangan, Kabuh and Notopuro Formations, and the Terrace and Recent alluvial deposits. The lower part of the Kalibeng Formation (late Miocene and early Pliocene) and the basement rocks (early Miocene, Oligocene, Eocene and pre-Tertiary) are not exposed in the Sangiran area. They are observed only as rock fragments and matrix in clastic substance of mud volcanoes.

Geological Stucture of the Sangiran Dome

The Sangiran Dome is an elliptical structure, approximately 4 km wide and 8 km long, trending in a NNE direction. Its geostructural center with mud volcanoes is situated in the southwestern part of the dome. This dome is made up of an outer elliptical ridge and an inner circular ridge, as well as the central hills. The outer ridge is comprised of the Kabuh and Notopuro Formations and coincides with the outline of the dome. The inner ridge consists of the Lower Lahar of the Pucangan Formation. The central hills, which are distributed along faults of two fault systems, are mainly built up by the Lower Lahar of the Pucangan Formation. A lowland between the outer and inner ridges is underlain by the Black Clay of the Pucangan Formation, and a lowland inside the inner circular ridge is mainly occupied by muddy and clayey sediments of the Kalibeng and Pucangan Formations. The lowland have been subjected to landsliding. In general, the geological structure and lithofacies of strata in the Sangiran dome are reflected in the above -mentioned topographic features.
The central part of the Sangiran Dome has a complicated geological structure which is obscured by landslide masses from place to place. Its elucidation is, however, important for obtaining the complete geological columns of the Kalibeng and Pucangan Formations. These geological columnar sections will clarify the stratigraphy of Pf mandible by Sartono (1978), a hominid skull by Jacob (unpublished), and a hominid skull by Jubiantono (unpublished), as well as the origin of mud volcanoes. The Sangiran Dome is characterized by radial and concentric faults, mud volcanoes and central depression blocks. The mud volcanoes erupted plastic mud with exotic blocks such as marl, shale, sandstone, nummulitic limestone, andesite, etc. The biggest block, 2.7 m long, is of Eocene nummulitic limestone. The natural methane gas is currently escaping from the smallest mud volcano northeast of Ngampon village. These erupted substances indicated that the diapiric flow originated from considerable depths. Thus, it is inferred that the process of updoming resulting from a diapiric rise of deepseated muddy sediments led to radial and concentric faults, eruption of mud volcanoes and depression of central blocks. This successive updoming process must have occurred after the deposition of the Notopuro Formation and before the deposition of the Terrace deposits.

2. Sambungmacan

In 1973, a fossil human skull was found during construction of a short canal at the meander site of the Solo River near Sambungmacan in Central Java. Although it is now possible to pinpoint the exact discovery point of the skull, there has been a continuing discussion concerning the age of this specimen and the stratigraphical sequence of the Sambungmacan area.
The first report on the stratigraphy of the area was by Hasibuan (1973), followed by Djubiantono (1977) and Jacob et al. (1978) with their combined study on stone artifacts.
An intensive geological survey of the area was undertaken by the CTA-41 Project during the 1976 and 1977 field seasons, and a preliminary report was issued by the Indonesia - Japan Cooperation Programme CTA-41 (1979). Sartono (1979) discussed the age of the skull and the stratigraphy of the area on the basis of these data, adding his own observations during a brief excursion and concluding as follows:
a) The geology of the area consists of the Upper Kalibeng Formation of the Late Pliocene age and the terrace deposits of Late Pleistocene age, and lacks the Pucangan and Kabuh Formations.
b) The skull from the short cut site belongs to Solo man (Homo erectus ngandongensis) of Late Pleistocene age on the basis of its morphology.
This conclusion, especially concerning stratigraphy, is not in accord with the previously expressed opinions by most of the above-mentions authors. Therefore, it is regarded as necessary that the present authors describe in details below the field evidence from their own intensive field work.

Geology and Stratigraphy

During the 1976 and 1977 field seasons, an intensive geological investigation was carried out to establish in detail the stratigraphic sequence of sediments exposed along a short cut canal of the area.
The oldest rocks exposed in the bottom of the canal consists of white to yellowish marly limestone with molluscan fossils. This limestone is correlated with the Kalibeng Formation on contained fossil. The gray silt intercalating with thin tuff and sand layers rest unconformably upon the tilted Kalibeng marly limestone. The abuntment relation between the silt and the Kalibeng limestone is clearly visible at the northern part of the canal.
Disconformably on the above-mentioned strata lie cross-laminated sand and gravel beds of weakly consolidated medium- to coarse-grained sand, pebble to cobble-size gravel and silt. The basal part of these beds, yielding many mammalian fossils, is slightly more consolidated. It gives a "grenzbank" appereance in some places.
All those older strata were then covered discordantly by horizontal river terrace deposits which consists of loose sand and gravel beds including black clays.
Field evidence indicates that the gray silt must be separated as a stratigraphic unit from the Kalibeng Formation because of the unconformable relation between them. It follows that the gray silt may be an equivalent of the Pucangan Formation, but definite conclusion must be postponed owing to a lack of fossil evidence and fission track dating. The cross-laminated sand and gravel beds are tentatively correlated with the Kabuh Formation by reason of stratigraphic position and their lithofacies.
The horizon of the skull of Solo man which was found from the short cut canal is still a problem needing clarification.

3. Trinil

Trinil in East Java has been known to paleoanthropologists since 1894 when Dubois announced the first discovery of a Pithecanthropus erectus skull on the east bank of the Solo River. The site lies about 60 km ENE of Solo and 3 km north of the Solo-Ngawi highway and has an almost flat topography in the meander area of the Solo River. The fossil site lies 175 m ENE from the present Pe monument.
The geology and stratigraphy of the Trinil and surrounding areas were first studied by Carthaus (1911) and Dozy (1911) who were members of the Selenka expedition to the area in 1907 and 1908, and had made some excavations at the Pithecanthropus site. Afterwards van Es (1931) and Duyfjes (1936) published the results of their investigations on the geology of the area. Most other investigators who studied the area after 1936 used Duyfjes' description as the basis of their investigations.
In 1976 and 1977, the former Geological Survey of Indonesia in collaboration with Quaternary scientists of Japan (CTA 41 Project), conducted a field survey in the Trinil area and produced a geological map on the scale of 1:250. The aim of the joint survey was to reconfirm the stratigrapic position of Pithecanthropus erectus of Dubois (1894).

Geology and Stratigraphy

Physiographically, Trinil and the surrounding areas belong to the southernmost part of the Kendeng anticlinorium. In this area, the Pliocene-Pleistocene sedimentary and volcanic rocks exhibit a homoclinal structure which gently dips southwards, although good outcrop can only be observed along the Solo River. Several geologic measured sections were made by the authors along the lower and upper stream of the Solo River between the villages of Papungan and Karanggeneng Kliteh. The older rock assemblage exposed in this area is a clay member of the so called Kalibeng Formation, unbedded and a deep marine facies. To the north of Pentuk village, the Solo River exposes the uppermost part of this member. This exposures consists of yellowish grey clay rich in planktonic foraminifera. The occurrence of Globorotalia plesiotumida, G. tumida, Sphaeroidinella dehiscens and Pulleniatina obliquiloculata indicates Early Pliocene age of Zone N.19 of Blow (1969).
The siltstone and limestone member of the Kalibeng Formation overlies conformably the clay member. It is typically of shallow marine sediment about 25 to 47 m thick. The siltstone itself is 0.5 to 37 m thick and contains abundant molluscs and benthonic foraminifera. Among the benthonic foraminiferal species Pseudorotalia indopacifica, P. gaimardii, Eponides praecintus and Cellanthus craticulatus are conspicuous. The limestone, about 1.5 to 15 m thick, is dominated in the lower part by corals and molluscs. This fauna, however, is lacking in the upper part of the unit. The uppermost part of the limestone unit is actually marl bearing carbonate fragments containing frequent planktonic foraminifera. Among the species recognized are Neogloboquadrina acostaensis, Globigerina praecalida, Globorotalia tumida, Hastigerina aequilateralis and Pulleniatina. Based on the above association, this part of the Kalibeng Formation is considered to be Pliocene in age.
The siltstone and limestone member is further covered conformably by another clay member of the same formation. This unit is a bluish-grey clay containing rounded fragments of carbonate rock ranging in size from a few millimeters to about 5 cm. It also contains abundant allochthonous planktonic foraminifera whose test surfaces had been eroded during transportation. The thickness of this unit ranges from 3 to 7 m.
The Pucangan Formation is the next younger unit conformably overlying the Kalibeng Formation. It is 22 to 32 m thick, consisting of volcanic breccia with intercalations of clay and grey siltstone. The breccia is dominantly composed of tuffaceous matrix with subrounded to rounded rock fragments mostly andesitic in composition, ranging in size of a few millimeters to more than 5 cm.
The Kabuh Formation which unconformably overlies the Pucangan Formation, 45 to 53 m thick, is dominantly composed of sandstone and siltstone with gravel bed intercalations. The sandstone is fine- to medium-grained and often exhibits cross-bedded structures. The Pithecanthropus erectus I of Dubois (1894) was confirmed to have been unearthed from the gravel bed located at the base of the Kabuh Formation.
The Notopuro Formation, more than 10 m thick, is composed of sand and gravel and frequently contains pumice balls.
The terrace deposits unconformably overlies the Kalibeng-Notopuro Formations. It is composed of gravel and sand not less than 4 m thick.

4. Mojokerto

A geological survey was carried out in an area around the site of Pithecanthropus modjokertensis north of Perning near Mojokerto, East Java. The purpose of this survey was to clarify the horizon of P. modjokertensis discovered in 1936 by Andoyo. The site of this fossil is shown in the geological maps of Duyfjes (1936) and von Koenigswald (1940). According to the lattter geological map, the site is located on the left side of a tributary of the Klagen River about 3 km north of Perning village. The horizon is also shown by Duyfjes (1936) as occurring in the d member, about 100 m thick, of the Pucangan Formation exposed in the northern wing of the Kedungwaru Anticline.
The Pucangan Formation in this area was divided into 7 members by Duyfjes (1936), designated a, b, c, d, e, f and g members in ascending order. The lithofacies of each member is as follows:

g. Coarse and fine-grained tuffaceous sandstone about 35 m thick.

f. Dolomite and/or tuffaceous sandstone with marine molluscs (Molluscan Horizon III). The thickness is about 10 m.

e. Greenish clay about 10 m thick.

d. Coarse-grained sandstones with irregular beds of sorted conglomerate containing andesite gravels. This member, in the lower part, contains intercalations of thin fine-grained tuffaceous sandstone beds. Its thickness is about 100 m.

c. Fine-grained tuffaceous sandstones with occasional clay intercalations. Its thickness is about 10 m.

b. Dolomitic, clayey, tuffaceous sandstones with marine molluscs and many coral pillars (Molluscan Horizon II). It is about 15 m thick and occasionally contains gravel.

a. Clayey, tuffaceous sandstones containing thin layers of tuffaceous sandstone. The thickness is about 25 m.

Stratigraphy

The study area is occupied by the Kabuh Formation and the volcanic facies of the Pucangan Formation of Duyfjes (1936). The axis of the Kedungwaru Anticline, trending approximately in an east-west direction, is located in the center of the surveyed area. The Pucangan and Kabuh Formations are distributed symmetrically in the north and south flanks of the anticline which is cyllindrical in shape with the dip of strata steeper further from the axis.
A rather continuous succession was observed along the road between Perning and Sumbertengah. Many outcrops occur, especially, on the northern flank of the anticline. The lithofacies of the Pucangan and Kabuh Formations discovered along the road crossing the northern flank are as follows.
The lowest member, consisting of a bluish gray, fine-grained sand with molluscs and foraminifera, corresponds to the Molluscan Horizon II of Duyfjes (1936). Overlying this are alternating layers of light gray sand and silt. Sand dominates in the upper layers.



Thursday, June 5, 2008

Early Men of Java

The island of Java was one of the big islands that were located in the Indonesian archipelago. The javanese inhabitants lived in the middle and eastern part of the island. The discovery of Pithecanthropus fossils by Eugene Dubois at the end of 19-th century was an epochmaking event in the history of the search for evidence of human evolution. Despite its importance, the find was for a long time the subject of controversies as to the genealogical position of specimens, for they were composed of a skull-cap having mixed characteristics of man and ape, and a femur possessing features comparable to those of modern man.

The most discussed of all human fossils was discovered in 1891 by E. Dubois, a Dutch army surgeon stationed on the island of Java. He had opened a quarry for vertebrate fossils in a 3-feet bed of gravel exposed in the bank of the Solo River, and there he came upon several human bones - a skull cap, a left thigh bone, fragment of nasal bones, and three teeth. Although each bone was isolated, and the thigh bone was found almost 50 feet from the skull, Dubois assumed that they belonged to one species if not to one individual, and recent application of the fluorine test confirms his inference that they are at least of the same age.

Java Man skullcap


Discovered by Eugene Dubois in 1891 near Trinil in Java. Its age is uncertain, but thought to be about 700,000 years. This find consisted of a flat, very thick skullcap, a few teeth, and a thigh bone found about 12 meters away (Theunissen, 1989). The brain size is about 940 cc. Trinkaus and Shipman (1992) state that most scientists now believe the femur is that of a modern human, but few of the other references mention this.

The skull cap was remarkably thick, the brow ridges very massive, and the forehead low and receding. The brain of this skull, estimated to have had a volume of 900 cubic centimeters, is intermediate in size between that of the largest apes (about 600 cubic centimeters) and the average for the lowest type of living men (about 1240 cubic centimeters). Moreover, the scars of attachment for the great neck muscles at the base of the skull clearly imply that the head was carried forward, as in the apes, instead of being well balanced on the neck, as in modern man.

Soon after discovery, this find was hailed as a "missing link" between the apes and man and was given the name Pithecanthropus erectus [Gr. pithecos, an ape + anthropos, a man]. Almost at once it became a subject of controversy. Skeptics argued that it was an abnormal individual, perhaps an idiot; but statisticians pointed out the extreme improbability of an abnormal individual being the sole survivor of a population to be preserved and discovered. All uncertainty was cleared up by the extensive and careful restudy of the area by Koenigswald between the years 1935 and 1940, which brought to light three additional skulls. The last nad most importance of these includes the upper jaw, part of the lower jaw, and several teeth, along with the posterior and basal part of the braincase. It is somewhat larger and more massive than the original skull and is believed to be that of a male, whereas the original was female. These skulls, fully confirm the interpretation previously made of the brain size and the shape of the head and face of Pithecanthropus, and prove beyond possible doubt that this is a well-defined but primitive human type.

Sangiran 2

Sangiran 2, "Pithecanthropus II", Homo erectus
A very similar but more complete braincase was found at Sangiran in Java in 1937 by G.H.R. von Koenigswald. It is even smaller, with a brain size of only 815 cc.


The small brain, low forehead, heavy brow ridges, protruding mouth, and receding chin give the skull a striking resemblance to that of a great ape, yet the brain is far larger than that of any great ape, the toothline is even, the canine teeth are relatively small and the dentition is in all respect human rather than simian; moreover, the straight thigh bone proves that he walked upright. Volcanics associated with the fossils indicate an age of about 500.000 years. There is no longer any doubt that Pithecanthropus was human and he is now placed in the genus Homo.

Six faunal zones are now known in the Pleistocene deposits of Java, and all the remains of Pithecanthropus are from a single one of these, the so called Trinil horizon. Other human remains of more modern type are found in some of the higher zones.