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The Sangiran dome, in Java's Solo basin, has yielded nearly 80 Homo erectus fossils, around 50 of which have known findspots. With a 1.66 [+ or -] 0.04 Ma [.sup.40]Ar/[.sup.39]Ar date on pumice reportedly associated with S27 and S31 (Swisher et al. 1994 - Science 283: 1118-1121) the dome may offer evidence that early Homo dispersed to East Asia during the earliest Pleistocene. Unfortunately, this pumice was sampled at Jokotingkir Hill, a central locality with complex litho-stratigraphic deformation and dubious specimen provenance (Larick et al. 2000 - Int. J. Primatol 21: 731-759). We address the sedimentary framework and [.sup.40]Ar/[.sup.39]Ar age for Homo erectus in the dome's SE quadrant, where fossiliferous Bapang (Kabuh) sediments have their largest exposure, least deformation, most complete tephro-stratigraphy, and greatest number of hominin findspots. At five locations, we identify a sequence of sedimentary cycles in which 28 hominin fossils are associated with epiclastic pumice. Eight hornblende separates produce [.sup.40]Ar/[.sup.39]Ar plateau ages ranging from 1.51 [+ or -] 0.08 Ma at the Bapang/Sangiran Formation contact zone, to 1.02 [+ or -] 0.06 Ma for the top of the hominin-bearing sequence. An intermediate level, which produced S17 and three nearly complete new crania, has an [.sup.40]Ar/[.sup.39]Ar age of about 1.25 Ma. The newly dated crania are from the following locations: Tanjung, Tjg-1993.05, comprising the calvarium, most of the maxilla with four teeth, and separate left temporal; Grogolwetan, Gwn-1993.09, conserving the left frontal, the sagittal part of the right frontal, parietals, posterior temporals and the occipital; and Sendangbusik, Sbk-1996.02, consisting of the temporals, portions of the parietals, and the occipital. The Bapang Formation represents an aggraded fluvial system built up on a number of energetic cycles. The new [.sup.40]Ar/[.sup.39]Ar dates are consistent within cycles and the sequence of dates matches the stratigraphy. Finally, new taphonomic evidence derived from the cycles suggests that H. erectus was living at or adjacent to areas where its fossils are found.

The stratigraphically lowest H. erectus fossils in the Solo basin occur in the upper Sangiran Formation and date to < 1.58 Ma. H. erectus fossils increase in abundance in the overlying Bapang Formation and occupy the area until 1.0 Ma. Archaeological sites in the Solo basin, such as Ngebung, are concentrated in the terraced gravels or the conglomeratic Grenzbank zone of the Bapang Formation. No lithologies reflecting low energy depositional environments have been identified or associated with any hominin locality. In August 2001 our team identified paleosols in the middle Bapang Formation and in the upper Sangiran Formation. These ancient soils mark the presence of habitable land surfaces in the Solo basin. Two paleosol horizons were found at Pucung, Bapang Formation. The soil features of these horizons are pedogenic carbonate accumulations, risoliths (root casts) of grassy plants, and insect burrows. Two other paleosol horizons were identified at stratigraphically-lower Bukuran, upper Sangiran Formation. Here the soils are associated with lake margin environments and exhibit characteristics of poor drainage, including gray colors, redoximorphic features, and the preservation of detrital organics including in situ tree trunks. The identification of paleosols in the Solo basin provides a robust depositional and environmental context for Homo erectus in Java. The buried soils will provide information about local and regional paleoenvironments prior to and during Homo erectus' occupation of central Java. Paleosol frequency through time will yield information about Homo erectus occupation patterns, and their identification should result in the discovery of new Homo erectus localities with primary contexts.

Recent fieldwork in the Ombilin Basin of west-central Sumatra resulted in the discovery of two distinct types of avian footprints, both referable to the ichnogenus Aquatilavipes. The footprints were discovered in the Oligocene Sawahlunto Formation in a creek side outcrop near the Kandi Ombilin Mine. Aquatilavipes wallacei is a small species of Aquatilavipes (∼ 19 mm wide; 27 mm long) with elongate third digits, wide total divarication angles (120–150°) and inwardly curved peripheral digits. Aquatilavipes ichnospecies A are also small traces (average 21 mm wide; 31 mm long) with elongate third digits and straight to slightly outwardly curved peripheral digits. These traces are similar in morphology to those of small modern shorebirds such as rails (Rallidae), sandpipers (Scolapacidae) or plovers (Charadriinae). The Sawahlunto traces occur in very fine-grained to fine-grained sandstone characterized by low-relief current ripples, many of which exhibit mud-draping. A low diversity invertebrate trace fossil assemblage consisting of Arenicolites, Diplocraterion, Planolites, Monocraterion, Skolithos and Coenobichnus co-occurs with the bird footprints. This succession is interpreted as intertidal sand flats. Probe and peck marks preserved on the same bedding planes as the bird footprints support the interpretation that these birds occupied the Kandi intertidal flats for foraging purposes. [ABSTRACT FROM PUBLISHER]

Worldwide, silicified woods are found in many geological formations. Significantly, the organic materials of wood are no longer dominant; almost all wood fossils have been mineralized into inorganic silica materials. These unique geological processes must be understood to develop better understanding on organic material fossilization, particularly in the micron scale. Therefore, our aim was to characterize the composition of silicified wood using comprehensive microanalysis. The methods utilized were XRF, ICP-MS, XRD, FTIR, and FE-EPMA. Specimens are from Jasinga, West Java, Indonesia. The results showed that wood silicification was controlled by the infiltration of silica from the host rock into the spaces of the wood structure. In Jasinga, they are controlled by Pliocene tuffaceous sedimentary rocks. The ratio of silica phases revealed a trend in the degree of silicification. Besides silica, the distribution of trace elements also demonstrates the geochemical interaction between the wood fossil and host rock. Wood fossils are affected by the gradual replacement of organic carbon-based materials with silica through silicification. Silica enrichment occurs in the internal of wood, facilitates permineralization and recrystallization. Silica replaces organic material and preserves the wood structures. The microanalytical approach provides comprehensive perspectives on wood petrification, leads to better insights for paleontological studies., (© 2024. The Author(s).)

Some of the earliest evidence for the presence of modern humans in rainforests has come from the fossil deposits of Lida Ajer in Sumatra. Two human teeth from this cave were estimated to be 73-63 thousand years old, which is significantly older than some estimates of modern human migration out of Africa based on genetic data. The deposits were interpreted as being associated with a rainforest environment based largely on the presence of abundant orangutan fossils. As well as the main fossil-bearing chamber, fossil-bearing passages are present below a sinkhole, although the relationship between the different fossil deposits has only been tenuously established. Here, we provide significant new sedimentological, geochronological and palaeoecological data aimed at reconstructing the speleological and environmental history of the cave and the clastic and fossil deposits therein. Our data suggest that the Lida Ajer fossils were deposited during Marine Isotope Stage 4, with fossils from the lower passages older than the main fossil chamber. Our use of stable carbon and oxygen isotope analyses of mammalian tooth enamel demonstrates that early humans probably occupied a closed-canopy forest very similar to those present in the region today, although the fossil orangutans may have occupied a slightly different niche. This article is part of the theme issue 'Tropical forests in the deep human past'.

Homo erectus is the founding early hominin species of Island Southeast Asia, and reached Java (Indonesia) more than 1.5 million years ago 1,2 . Twelve H. erectus calvaria (skull caps) and two tibiae (lower leg bones) were discovered from a bone bed located about 20 m above the Solo River at Ngandong (Central Java) between 1931 and 1933 3,4 , and are of the youngest, most-advanced form of H. erectus 5-8 . Despite the importance of the Ngandong fossils, the relationship between the fossils, terrace fill and ages have been heavily debated 9-14 . Here, to resolve the age of the Ngandong evidence, we use Bayesian modelling of 52 radiometric age estimates to establish-to our knowledge-the first robust chronology at regional, valley and local scales. We used uranium-series dating of speleothems to constrain regional landscape evolution; luminescence, 40 argon/ 39 argon ( 40 Ar/ 39 Ar) and uranium-series dating to constrain the sequence of terrace evolution; and applied uranium-series and uranium series-electron-spin resonance (US-ESR) dating to non-human fossils to directly date our re-excavation of Ngandong 5,15 . We show that at least by 500 thousand years ago (ka) the Solo River was diverted into the Kendeng Hills, and that it formed the Solo terrace sequence between 316 and 31 ka and the Ngandong terrace between about 140 and 92 ka. Non-human fossils recovered during the re-excavation of Ngandong date to between 109 and 106 ka (uranium-series minimum) 16 and 134 and 118 ka (US-ESR), with modelled ages of 117 to 108 thousand years (kyr) for the H. erectus bone bed, which accumulated during flood conditions 3,17 . These results negate the extreme ages that have been proposed for the site and solidify Ngandong as the last known occurrence of this long-lived species.

Sangiran (Solo Basin, Central Java, Indonesia) is the singular Homo erectus fossil locale for Early Pleistocene Southeast Asia. Sangiran is the source for more than 80 specimens in deposits with (40)Ar/(39)Ar ages of 1.51-0.9 Ma. In April 2001, we recovered a H. erectus left maxilla fragment (preserving P(3)- M(2)) from the Sangiran site of Bapang. The find spot lies at the base of the Bapang Formation type section in cemented gravelly sands traditionally called the Grenzbank Zone. Two meters above the find spot, pumice hornblende has produced an (40)Ar/(39)Ar age of 1.51 ± 0.08 Ma. With the addition of Bpg 2001.04, Sangiran now has five H. erectus maxillae. We compare the new maxilla with homologs representing Sangiran H. erectus, Zhoukoudian H. erectus, Western H. erectus (pooled African and Georgian specimens), and Homo habilis. Greatest contrast is with the Zhoukoudian maxillae, which appear to exhibit a derived pattern of premolar-molar relationships compared to Western and Sangiran H. erectus. The dental patterns suggest distinct demic origins for the earlier H. erectus populations represented at Sangiran and the later population represented at Zhoukoudian. These two east Asian populations, separated by 5000 km and nearly 800 k.yr., may have had separate origins from different African/west Eurasian populations., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Skull IX (Tjg-1993.05) was unearthed from the upper stratigraphic zone (Bapang-AG levels) of the hominin-bearing sequence in Sangiran. This remarkably complete cranial specimen of Homo erectus from the early Pleistocene of Java preserves substantial portions of the vault and face. However, the distortion present in the original reconstruction has hampered detailed documentation of its morphological characteristics. We here report a new reconstruction of Skull IX that successfully recovers the original morphology and significantly differs from previous reconstructions. Detailed morphological description and the results of initial comparative analyses based on this new reconstruction are provided. The endocranial volume of Skull IX was measured as 870 cc using micro-CT data. The neurocranium of Skull IX is slightly smaller than the so far recorded smallest cranium from this zone, suggesting this individual was female. In most, but not all, aspects of the cranial vault form, details of the external surface structures, and facial morphology, Skull IX exhibits numerous similarities to the other Bapang-AG H. erectus specimens, indicating that it belonged to the Bapang-AG H. erectus population. Drawing on the expanded fossil sample of this chronoregional H. erectus group, we discuss their evolutionary status, degree of sexual dimorphism, and facial morphological variation in Afro-Asian earlier Homo specimens., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

A sequence of paleosols in the Solo Basin, Central Java, Indonesia, documents the local and regional environments present when Homo erectus spread through Southeast Asia during the early Pleistocene. The earliest human immigrants encountered a low-relief lake-margin landscape dominated by moist grasslands with open woodlands in the driest landscape positions. By 1.5 Ma, large streams filled the lake and the landscape became more riverine in nature, with riparian forests, savanna, and open woodland. Paleosol morphology and carbon isotope values of soil organic matter and pedogenic carbonates indicate a long-term shift toward regional drying or increased duration of the annual dry season through the early Pleistocene. This suggests that an annual dry season associated with monsoon conditions was an important aspect of the paleoclimate in which early humans spread from Africa to Southeast Asia.

The Sangiran dome is the primary stratigraphic window for the Plio-Pleistocene deposits of the Solo basin of Central Jawa. The dome has yielded nearly 80 Homo erectus fossils, around 50 of which have known findspots. With a hornblende (40)Ar/(39)Ar plateau age of 1.66 +/- 0.04 mega-annum (Ma) reportedly associated with two fossils [Swisher, C.C., III, Curtis, G. H., Jacob, T., Getty, A. G., Suprijo, A. & Widiasmoro (1994) Science 263, 1118-1121), the dome offers evidence that early Homo dispersed to East Asia during the earliest Pleistocene. Unfortunately, the hornblende pumice was sampled at Jokotingkir Hill, a central locality with complex lithostratigraphic deformation and dubious specimen provenance. To address the antiquity of Sangiran H. erectus more systematically, we investigate the sedimentary framework and hornblende (40)Ar/(39)Ar age for volcanic deposits in the southeast quadrant of the dome. In this sector, Bapang (Kabuh) sediments have their largest exposure, least deformation, and most complete tephrostratigraphy. At five locations, we identify a sequence of sedimentary cycles in which H. erectus fossils are associated with epiclastic pumice. From sampled pumice, eight hornblende separates produced (40)Ar/(39)Ar plateau ages ranging from 1.51 +/- 0.08 Ma at the Bapang/Sangiran Formation contact, to 1.02 +/- 0.06 Ma, at a point above the hominin-bearing sequence. The chronological sequence of (40)Ar/(39)Ar ages follows stratigraphic order across the southeast quadrant. An intermediate level yielding four nearly complete crania has an age of about 1.25 Ma.