Edited by: Daniel Nývlt, Masaryk University, Czechia
Reviewed by: Cynthia M. Fadem, Earlham College, United States; Nadia Solovieva, University College London, United Kingdom
This article was submitted to Quaternary Science, Geomorphology and Paleoenvironment, a section of the journal Frontiers in Earth Science
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Oldupai Gorge is located within the Ngorongoro Conservation Area, a UNESCO World Heritage Site in northern Tanzania along the western margin of the East African Rift System. Oldupai's sedimentary record contains inter-stratified stone tool industries associated with the Earlier, Middle, and Later Stone Age. While diachronic technological change is perceptible, the totality of locally available rocks remained largely unchanged through time. Here, thin section petrography, Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy, and Electron Probe Micro Analysis were employed to characterize source lithologies in the Oldupai region. One of our goals was to determine if outcrops have rock types with unique mineral assemblages amenable for sourcing lithic artifacts. Petrographic analysis of 62 lithologic samples collected in primary and secondary positions reveal discriminatory differences. More precisely, five outcrops have quartzites with unique mineral assemblages, five outcrops have meta-granites with unique mineral assemblages, Engelosin phonolite samples are texturally and mineralogically unique, and magmatic samples recovered in secondary position may be sourced to their volcanic center. Our results demonstrate it is feasible to discriminate source materials using mineralogy, which implies that sourcing lithic artifacts is possible. For proof of concept, we assign the source/s of previously described fuchsitic quartzite artifacts from three archaeological sites at Oldupai to two nearby outcrops. Additional archaeological testing will allow researchers to glean new understandings of hominin behavior and stone procurement in the Oldupai paleobasin.
Rocks used for artifact manufacture are alternatively known as lithic raw materials and occur as mineral aggregates of igneous, metamorphic, and sedimentary origin that are non-renewable and spatially exhaustible over a non-geological timeframe (Kyara,
In this study, we characterize a range of lithologies that were available to hominins at Oldupai Gorge using a combination of thin section petrography, Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and Electron Probe Micro Analysis (EPMA). One of our goals was to determine the feasibility of sourcing lithic artifacts based on their mineralogy (cf. Soto et al.,
We show that several outcrops near Oldupai Gorge have lithologies that can be identified by a unique combination of minerals which implies that sourcing lithic artifacts based on mineralogy is a viable technique. This is evidenced by the similarity of rock specimens from the Naibor Soit Kubwa and Naibor Soit Ndogo outcrops to previously described Oldowan and Acheulean quartzite artifacts from three archaeological sites. Our results not only establish the merit of further archaeological testing scaffolded by additional characterization efforts, but also contribute to the growing body of work which shows that quartzitic outcrops can be differentiated from each other despite their assumed homogeneity on a regional scale (Ebright,
Oldupai Gorge is located on the boundary between the Tanzania Craton to the west and the Mozambique Belt to the east (
Variably overlying the basement rocks of the Tanzania Craton and the Mozambique Belt and obscuring their contacts are volcanic rocks of the Ngorongoro Volcanic Highlands (NVH) associated with the East African Rift System, which is an active intra-continental extension zone (
The Main and Side Gorge cut into the basement rocks of Eastern Serengeti Plains and provide good exposures of the stratigraphy. During the Early Pleistocene, Oldupai was an endorheic, rift-shoulder sedimentary basin that hosted a saline alkaline lake fed by stream networks from the NVH to the west, and characterized by abruptly rising metamorphic inselbergs associated with the Mozambique Belt (Hay,
Lithic industries including Earlier Stone Age (ESA), Middle Stone Age, and Later Stone Age assemblages are preserved in Oldupai's sedimentary record spanning from the Early Pleistocene to the Holocene (Leakey,
Our ability to understand hominin behavior from a techno-ecological perspective is hindered by two factors. First, it is well-documented that raw material morphometry and mechanical properties, at and beyond Oldupai, affect the classification of artifact assemblages (Leakey,
As part of the
Sample position, outcrop/source, ID, rock type, raw material group, number of thin sections per sample, and samples analyzed by SEM-EDS/EPMA.
Primary | Endonyo Osunyai | Endonyo Osunyai 1 | Quartzite | W3 | 1 | No |
Endonyo Osunyai 2 | Quartzite | W3 | 1 | No | ||
Endonyo Osunyai 4A/B | Quartzite | GR2 | 2 | No | ||
Engelosin | Engelosin 2 | Phonolite | n/a | 1 | No | |
Engelosin 5A/B | Phonolite | n/a | 2 | No | ||
Engelosin 6A/B | Phonolite | n/a | 2 | No | ||
Engelosin 10A/B | Phonolite | n/a | 2 | No | ||
Gol Mountains | DDD1 | Quartzite | GR2 | 1 | No | |
JJJ1 | Meta-monzo-granite | n/a | 1 | No | ||
KKK1 | Meta-quartz-rich granitoid | n/a | 1 | No | ||
OOO1 | Feldspar | n/a | 1 | No | ||
PPP1 | Quartzite | W3 | 1 | No | ||
RRR1 | Quartzite | G1 | 1 | No | ||
SSS1 | Quartzite | GR2 | 1 | No | ||
TTT1 | Meta-quartz-rich granitoid | n/a | 1 | No | ||
UUU1 | Meta-quartz-rich granitoid | n/a | 1 | No | ||
Granite Falls | Granite Falls 1A/B | Granite gneiss | n/a | 2 | No | |
Granite Falls 2 | Granite gneiss | n/a | 1 | No | ||
Kelogi | Kelogi 1 | Granite gneiss | n/a | 1 | No | |
Kelogi 3 | Granite gneiss | n/a | 1 | No | ||
Kelogi 10 | Granite gneiss | n/a | 1 | Yes | ||
Naibor Soit Kubwa | Naibor Soit Kubwa N042 | Quartzite | R3 | 1 | No | |
Naibor Soit Kubwa E039 | Quartzite | W1 | 1 | No | ||
Naibor Soit Kubwa S06 | Quartzite | W3 | 1 | No | ||
Naibor Soit Kubwa 1 | Quartzite | R3 | 1 | No | ||
Naibor Soit Kubwa 2 | Quartzite | W3 | 1 | No | ||
Naibor Soit Kubwa 6 | Quartzite | GR1 | 1 | Yes | ||
Naibor Soit Kubwa 8 | Quartzite | R3 | 1 | No | ||
Naibor Soit Kubwa 11 | Quartzite | W3 | 1 | No | ||
Naibor Soit Kubwa 13 | Quartzite | R3 | 1 | No | ||
Naibor Soit Kubwa 14 | Quartzite | W2 | 1 | No | ||
Naibor Soit Kubwa 24 | Quartzite | W2 | 1 | No | ||
Naibor Soit Kubwa 27 | Quartzite | R3 | 1 | No | ||
Naibor Soit Kubwa 28 | Quartz amphibolite | n/a | 1 | No | ||
Naibor Soit Kubwa 31 | Quartzite | G1 | 1 | No | ||
Naibor Soit Kubwa 32 | Quartzite | GR1 | 1 | No | ||
Naibor Soit Kubwa 33 | Quartzite | GR1 | 1 | No | ||
Naibor Soit Ndogo | Naibor Soit Ndogo 6A/B | Quartzite | W3 | 2 | No | |
Naibor Soit Ndogo 8 | Quartzite | W3 | 1 | No | ||
Naibor Soit Ndogo 13 | Quartzite | W2 | 1 | Yes | ||
Naibor Soit Ndogo 14 | Quartzite | G1 | 1 | No | ||
Naibor Soit Ndogo 15 | Quartzite | W3 | 1 | No | ||
Naisiusiu | Naisiusiu 3 | Meta-syeno-granite | n/a | 1 | No | |
Naisiusiu 4 | Quartzite | GR2 | 1 | Yes | ||
Naisiusiu 7 | Quartzite | GR1 | 1 | Yes | ||
Naisiusiu 8 | Mica schist | n/a | 1 | No | ||
Naisiusiu 9 | Quartzite | W4 | 1 | No | ||
Naisiusiu 13 | Quartzite | GR1 | 1 | No | ||
Naisiusiu 14 | Quartzite | W3 | 1 | No | ||
Oittii | Oittii 1A/B | Quartzite | GR2 | 2 | No | |
Oittii 3 | Quartzite | W4 | 1 | No | ||
Oittii 4 | Quartzite | GR2 | 1 | No | ||
Oittii 5A/B | Quartzite | GR2 | 2 | No | ||
Secondary | Gol Mountains | III1 | Hornblende granofels | n/a | 1 | Yes |
Granite Falls | Granite Falls 3A/B | Nephelinite | n/a | 2 | No | |
Granite Falls 4A/B | Quartzite | W3 | 2 | No | ||
Kelogi | Kelogi 9 | Quartzite | GR3 | 1 | Yes | |
Naisiusiu | Naisiusiu 12 | Nephelinite | n/a | 1 | Yes | |
Olbalbal | A1A/B | Nephelinite | n/a | 2 | Yes | |
A2 | Basalt | n/a | 1 | No | ||
A5A/B | Basalt | n/a | 2 | No | ||
A6 | Trachyandesite/basalt | n/a | 1 | Yes |
We conducted a macroscopic description of our samples as part of our multi-scalar characterization of raw materials (Soto et al.,
Ten thin sections analyzed for this study were prepared at the Geoscience Research Laboratory (University of Calgary). The remaining samples were thin sectioned at the Tropical Archaeology Lab (University of Calgary) where these were cut flat (Trim Saw, TS10, Lortone Inc.; IsoMet 4000 Linear Precision Saw), slide-mounted on frosted slides (27 × 46 mm) (Cast N' Vac 1000 Castable Vacuum System), ground to 30–35 μm (PetroThin Thin Sectioning System), and polished (Metaserv 2000 Grinder Polisher).
Visually estimated modal percentages per sample.
Primary | Endonyo Osunyai | Endonyo Osunyai 1 | Quartzite | Quartz (98); muscovite (2); opaque (<1); rutile (<1) |
Endonyo Osunyai 2 | Quartzite | Quartz (98); muscovite (2); opaque (<1) | ||
Endonyo Osunyai 4A | Quartzite | Quartz (79); alkali feldspar (15); muscovite (5); hematite (1) | ||
Endonyo Osunyai 4B | Quartzite | Quartz (78); alkali feldspar (10); muscovite (10); hematite (2) | ||
Engelosin | Engelosin 2 | Phonolite | Sanidine (5); nepheline (1); titanite (<1); sericite (<1) | |
Engelosin 5A | Phonolite | Sanidine (2); nepheline (1); augite (1); titanite (<1); sericite (<1) | ||
Engelosin 5B | Phonolite | Nepheline (1); sanidine (1); augite (1); sericite (<1); titanite (<1) | ||
Engelosin 6A | Phonolite | Sanidine (1); nepheline (<1); augite (<1); sericite (<1); titanite (<1) | ||
Engelosin 6B | Phonolite | Nepheline (1); sanidine (1); augite (<1); sericite (<1) | ||
Engelosin 10A | Phonolite | Sanidine (5); augite (<1); titanite (<1); nepheline (<1) | ||
Engelosin 10B | Phonolite | Sanidine (5); titanite (1); augite (1); nepheline (<1) | ||
Gol Mountains | DDD1 | Quartzite | Quartz (90); muscovite (10); alkali feldspar (<1) | |
JJJ1 | Meta-monzo-granite | Quartz (45); alkali feldspar (40); biotite (15); plagioclase (<1); rutile (<1) | ||
KKK1 | Meta-quartz-rich granitoid | Quartz (60); alkali feldspar (20); biotite (12); hornblende (6); plagioclase (2) | ||
OOO1 | Feldspar | Microcline (73); albite (25); hematite (1); opaque (1); sanidine (<1) | ||
PPP1 | Quartzite | Quartz (95); muscovite (5); rutile (<1); opaque (<1) | ||
RRR1 | Quartzite | Quartz (90); muscovite (10); rutile (<1) | ||
SSS1 | Quartzite | Quartz (92); muscovite (8); rutile (<1) | ||
TTT1 | Meta-quartz-rich granitoid | Quartz (70); biotite (10); plagioclase (10); alkali feldspar (8); opaque (2) | ||
UUU1 | Meta-quartz-rich granitoid | Quartz (70); biotite (10); alkali feldspar (10); plagioclase (5); opaque (3); muscovite (2) | ||
Granite Falls | Granite Falls 1A | Granite gneiss | Quartz (50); alkali feldspar (30); biotite (15); muscovite (5); plagioclase (<1) | |
Granite Falls 1B | Granite gneiss | Quartz (60); alkali feldspar (20); biotite (10); muscovite (8); plagioclase (2) | ||
Granite Falls 2 | Granite gneiss | Quartz (69); alkali feldspar (15); plagioclase (10); muscovite (5); biotite (1) | ||
Kelogi | Kelogi 1 | Granite gneiss | Quartz (40); aegirine (20); plagioclase (15); alkali feldspar (15); hornblende (10) | |
Kelogi 3 | Granite gneiss | Quartz (45); aegirine (20); hornblende (12); plagioclase (12); hematite (8); alkali feldspar (3) | ||
Kelogi 10 | Granite gneiss | Plagioclase (25); quartz (25); hornblende (20); aegirine (20); alkali feldspar (10); titanite (<1); biotite (<1); zircon (<1) | ||
Naibor Soit Kubwa | Naibor Soit Kubwa N042 | Quartzite | Quartz (85); muscovite (15); hematite (<1) | |
Naibor Soit Kubwa E039 | Quartzite | Quartz (92); muscovite (8) | ||
Naibor Soit Kubwa S06 | Quartzite | Quartz (95); muscovite (5) | ||
Naibor Soit Kubwa 1 | Quartzite | Quartz (93); muscovite (5); hematite (1); rutile (1) | ||
Naibor Soit Kubwa 2 | Quartzite | Quartz (95); muscovite (5); rutile (<1); opaque (<1) | ||
Naibor Soit Kubwa 6 | Quartzite | Quartz (92); muscovite (5); rutile (1); opaque (1); fuchsite (1); anhydrite (<1) | ||
Naibor Soit Kubwa 8 | Quartzite | Quartz (94); muscovite (6); opaque (<1); rutile (<1) | ||
Naibor Soit Kubwa 11 | Quartzite | Quartz (98); muscovite (2); rutile (<1) | ||
Naibor Soit Kubwa 13 | Quartzite | Quartz (92); muscovite (8); rutile (<1) | ||
Naibor Soit Kubwa 14 | Quartzite | Quartz (92); muscovite (8) | ||
Naibor Soit Kubwa 24 | Quartzite | Quartz (99); muscovite (1); opaque (<1) | ||
Naibor Soit Kubwa 27 | Quartzite | Quartz (70); muscovite (30) | ||
Naibor Soit Kubwa 28 | Quartz amphibolite | Hornblende (40); epidote (32); quartz (24); opaque (3); plagioclase (1); calcite (<1) | ||
Naibor Soit Kubwa 31 | Quartzite | Quartz (92); muscovite (8) | ||
Naibor Soit Kubwa 32 | Quartzite | Quartz (85); muscovite (14); rutile (1); fuchsite (<1) | ||
Naibor Soit Kubwa 33 | Quartzite | Quartz (97); muscovite (3); magnetite (<1) | ||
Naibor Soit Ndogo | Naibor Soit Ndogo 6A | Quartzite | Quartz (95); muscovite (5) | |
Naibor Soit Ndogo 6B | Quartzite | Quartz (95); muscovite (5) | ||
Naibor Soit Ndogo 8 | Quartzite | Quartz (98); muscovite (2) | ||
Naibor Soit Ndogo 13 | Quartzite | Quartz (96); muscovite (3); fuchsite (1); rutile (<1); opaque (<1); anhydrite (<1) | ||
Naibor Soit Ndogo 14 | Quartzite | Quartz (98); muscovite (2); fuchsite (<1) | ||
Naibor Soit Ndogo 15 | Quartzite | Quartz (95); muscovite (5); opaque (<1); hematite (<1); rutile (<1) | ||
Naisiusiu | Naisiusiu 3 | Meta-syeno-granite | Quartz (45); alkali feldspar (35); plagioclase (10); opaque (7); biotite (2); hornblende (1) | |
Naisiusiu 4 | Quartzite | Quartz (85); biotite (13); muscovite (1); opaque (Cr-bearing rutile) (1); secondary mica (1); plagioclase (<1); albite (<1); apatite (<1); anhydrite (<1); tschermakite (<1) | ||
Naisiusiu 7 | Quartzite | Quartz (94); chlorite (4); muscovite (1); opaque (1); calcite (<1); alkali feldspar (<1); plagioclase (<1); apatite (<1); glauconite (<1) | ||
Naisiusiu 8 | Mica schist | Muscovite (75); quartz (15); biotite (10); plagioclase (<1) | ||
Naisiusiu 9 | Quartzite | Quartz (95); muscovite (5) | ||
Naisiusiu 13 | Quartzite | Quartz (97); muscovite (2); hematite (1); opaque (<1) | ||
Naisiusiu 14 | Quartzite | Quartz (94); muscovite (5); opaque (1) | ||
Oittii | Oittii 1A | Quartzite | Quartz (93); muscovite (3); hematite (3); rutile (1) | |
Oittii 1B | Quartzite | Quartz (93); muscovite (3); hematite (3); rutile (1) | ||
Oittii 3 | Quartzite | Quartz (85); muscovite (10); alkali feldspar (5); plagioclase (<1) | ||
Oittii 4 | Quartzite | Quartz (96); muscovite (2); hematite (1); rutile (1) | ||
Oittii 5A | Quartzite | Quartz (85); muscovite (15); alkali feldspar (<1) | ||
Oittii 5B | Quartzite | Quartz (85); muscovite (15); alkali feldspar (<1) | ||
Secondary | Gol Mountains | III1 | Hornblende granofels | Hornblende (50); quartz (48); opaque (ilmenite) (2); alkali feldspar (<1); plagioclase (<1) |
Granite Falls | Granite Falls 3A | Nephelinite | Nepheline (5); opaque (3); aegirine-augite (<1); sanidine (<1) | |
Granite Falls 3B | Nephelinite | Nepheline (5); opaque (3); aegirine-augite (<1); sanidine (<1) | ||
Granite Falls 4A | Quartzite | Quartz (95); muscovite (5) | ||
Granite Falls 4B | Quartzite | Quartz (95); muscovite (5) | ||
Kelogi | Kelogi 9 | Quartzite | Quartz (86); staurolite (8); muscovite (3); kyanite (2); opaque (ilmenite) (1); apatite (<1); zircon (<1) | |
Naisiusiu | Naisiusiu 12 | Nephelinite | Nepheline (5); aegirine-augite (1); sanidine (<1); hornblende (<1); opaque (ilmenite) (<1); alkali feldspar (<1); apatite (<1); secondary quartz (<1) | |
Olbalbal | A1A | Nephelinite | Nepheline (65); aegirine-augite (10); hornblende (1); titanite (<1); titanoaugite (<1); wollastonite (<1); apatite (<1); calcic plagioclase (<1); Cl-bearing silicates (<1) | |
A1B | Nephelinite | Nepheline (65); aegirine-augite (10); hornblende (1); titanite (<1); titanoaugite (<1); wollastonite (<1); apatite (<1); calcic plagioclase (<1); Cl-bearing silicates (<1) | ||
A2 | Basalt | Plagioclase (20); opaque (1); augite (1); olivine (1) | ||
A5A | Basalt | Plagioclase (1); augite (<1) | ||
A5B | Basalt | Plagioclase (1); augite (<1) | ||
A6 | Trachyandesite/basalt | Plagioclase (1); kaersutite (1); augite (<1); alkali feldspar (<1); pyroxene (<1); ilmenite (<1); magnetite (<1) |
A total of 74 thin sections were analyzed using a Leitz HM-POL petrographic microscope (2.5, 4, 10, 40×) (
Ten thin sections (
The 10 thin sections analyzed by SEM-EDS were also studied by EPMA (
The following sections, organized alphabetically by outcrop name, provide the geologic context for each outcrop and petrographic descriptions of samples.
Endonyo Osunyai consists of sporadically exposed quartzites and gneisses along a ~100 m long stretch northwest of Naibor Soit Kubwa (
Endonyo Osunyai:
Prior studies have identified gneiss and quartzite at Endonyo Osunyai, but no petrographic descriptions are available (Hay,
Endonyo Osunyai 2:
Engelosin is a 150 m-high, weathered and oxidized phonolitic volcanic neck north of Oittii (
Engelosin phonolite is green to gray, fine- to medium-grained, and exhibits a variety of porphyritic and vesicular textures. Previous studies show alkali feldspar (anorthoclase and sanidine), augite, nepheline, aegirine, analcime, titanite, and apatite as constituent minerals (Hay,
Textural data per magmatic sample.
Engelosin 2 | Phonolite | Microporphyritic | Flow-aligned | Light-green | Trachytic |
Engelosin 5A | Phonolite | Microporphyritic | Felty | Light-green | Felty |
Engelosin 5B | Phonolite | Microporphyritic | Felty | Light-green | Felty |
Engelosin 6A | Phonolite | Microporphyritic | Flow-aligned | Light-green | Trachytic |
Engelosin 6B | Phonolite | Microporphyritic | Flow-aligned | Light-green | Trachytic |
Engelosin 10A | Phonolite | Microporphyritic | Flow-aligned | Light-gray | Trachytic |
Engelosin 10B | Phonolite | Microporphyritic | Flow-aligned | Light-gray | Trachytic |
Granite Falls 3A | Nephelinite | Microporphyritic | Weakly aligned | Light-brown | Flow-aligned |
Granite Falls 3B | Nephelinite | Microporphyritic | Weakly aligned | Light-brown | Flow-aligned |
Naisiusiu 12 | Nephelinite | Microporphyritic | Flow-aligned | Brown-gray | Flow-aligned |
A1A | Nephelinite | Porphyritic | Weakly aligned | Dark-brown | Weakly aligned |
A1B | Nephelinite | Porphyritic | Weakly aligned | Dark-brown | Weakly aligned |
A2 | Basalt | Porphyritic | Flow-aligned | Light-gray | Trachytic |
A5A | Basalt | Porphyritic | Flow-aligned | Light-gray | Trachytic |
A5B | Basalt | Porphyritic | Flow-aligned | Light-gray | Trachytic |
A6 | Trachyandesite/basalt | Microporphyritic | Felty | Light-gray | Felty |
The Gol Mountains refers to primarily metamorphic inselbergs that transition northwards into a mountain range. These inselbergs begin to outcrop ~4 km north of Engelosin and belong to the Mozambique Belt (
One of the most iconic inselbergs of the Gol Mountains is Soit Nasera (
Previous studies reported quartzite at Olongojoo and near Soit Nasera but no detailed descriptions are available (Hay,
Meta-granites contain quartz, alkali feldspar, biotite, hornblende, plagioclase, rutile, and muscovite (
One sample of fine-grained leucocratic feldspar from Soit Nasera contains microcline, albite, hematite, opaque crystals, and sanidine (
One sample of fine-grained homeoblastic granofels contains hornblende, quartz, ilmenite, alkali feldspar, and plagioclase (
Granite Falls comprise metamorphosed granitic lithologies that underlie the sedimentary units in the western Oldupai paleobasin (Hay,
Granite Falls:
Hay (
One sample of nephelinite recovered from the riverbed (
One sample of quartzite discovered in the riverbed (
Kelogi refers to a series of northeast-southwest trending granite gneiss inselbergs west of the Side Gorge (
Previous studies of granite gneiss have reported quartz, orthoclase, albite, aegirine, hornblende, biotite, and garnet (Hay,
One quartzite sample in secondary position is fine-grained, and has a mineral assemblage of quartz, staurolite, muscovite, kyanite, ilmenite, zircon, and apatite (
Kelogi 9:
X-ray spectra (EDS) of minerals obtained using EPMA:
Naibor Soit Kubwa is a ~1.8 km-long, northwest-southeast trending quartzitic and gneissic inselberg west of Naibor Soit Ndogo (
Previous studies have identified gneiss and coarse-grained quartzite with rare muscovite (Hay,
Fine-grained gneissose (defined by hornblende) quartz amphibolite was sampled from a previously unrecorded meta-mafic dyke cross-cutting the quartzite-dominated inselberg (
Naibor Soit Ndogo is a ~1 km-long, northwest-southeast trending quartzitic inselberg east of Naibor Soit Kubwa (
Naibor Soit Ndogo:
Previous studies have identified coarse-grained quartzite with a mineral assemblage of quartz and rare muscovite (Leakey,
Naisiusiu is a low-lying, east-west trending quartzitic, schistose, and meta-granitic outcrop ~3 km southeast of Granite Falls (
Previous studies on quartzite have identified quartz, microcline, muscovite, garnet, kyanite, and staurolite (Hay,
Naisiusiu 14:
Previous studies on granite gneiss have identified quartz, microcline, plagioclase, aegirine, hornblende, titanite, and biotite as mineral constituents (Hay,
One sample of medium- to fine-grained mica schist contains muscovite, quartz, biotite, and plagioclase (
One sample of nephelinite recovered on the surface of the outcrop contains nepheline, aegirine-augite, sanidine, and hornblende microphenocrysts included in a flow-aligned brown-gray groundmass with devitrified glass and minor amounts of oxides (
Oittii is a low-lying, quartzitic and schistic outcrop north of Naibor Soit Ndogo (
Previous studies have identified mica schist and quartzite but no petrographic descriptions are available (Leakey,
Olbalbal is a fault graben located between Ngorongoro/Olmoti and Oldupai's First Fault (
Sample A1 is a nephelinite and contains nepheline phenocrysts and lesser amounts of aegirine-augite, hornblende, and titanite included in a dark-brown groundmass (
The non-diagnostic mineral assemblages for the three remaining samples (A2, A5A/B, and A6) hindered satisfactory classification (
Sample A2 is an inequigranular, flow-aligned, porphyritic basalt with plagioclase (20%), opaque crystals (1%), augite (1%), and olivine (1%) phenocrysts included in a trachytic light-gray plagioclase-rich groundmass. Plagioclase phenocrysts are occasionally zoned and have a glomerophyric texture. Olivine phenocrysts are occasionally altered evidenced by internal cracks filled with opaque material.
Sample A5A/B is a flow-aligned, porphyritic basalt with plagioclase (1%) and augite (<1%) phenocrysts included in a trachytic light-gray plagioclase-rich groundmass. Vesicles are occasionally filled with secondary micritic carbonate crystals that precipitated from seasonal standing water rather than having crystallized from molten-carbonate magma.
Sample A6 was identified as a trachyandesite/basalt from Olmoti based on the presence of kaersutite (
There are a minimum of four varieties of igneous rocks that can be found at Olbalbal (
Quartzites and meta-granites form the most abundant raw materials in the outcrops described in this study. These lithologies show variations in modal mineralogy and texture that may be used to group them into distinct varieties. The following sections describe the quartzite and meta-granite varieties deemed archaeologically relevant for sourcing.
From the 16 quartzite varieties, two co-occur at two outcrops (
Variety 8 from Naibor Soit Ndogo is a coarse-grained fuchsite-bearing quartzite. Similar modal percentages of quartz, muscovite, fuchsite, rutile, and opaque crystals can also be found at Naibor Soit Kubwa in Variety 6. The presence of fuchsite at both outcrops is unique compared to all sampled outcrops in the Oldupai paleobasin, while the presence of magnetite is unique to quartzite from Naibor Soit Kubwa. Samples classified in Variety 6 and 8 fall within our previously established Raw Material Group Green 1 (Soto et al.,
Six other quartzite varieties uniquely occur at an individual outcrop (
Variety 2 is a coarse-grained alkali feldspar-bearing quartzite from Endonyo Osunyai. The modal percentages of quartz (~80%) and alkali feldspar (10–15%) are unique to this outcrop.
Variety 5 is a coarse- to fine-grained muscovite-rich quartzite from Naibor Soit Kubwa. The modal percentages of quartz (70%) and muscovite (~30%) are unique to this outcrop.
Variety 10 is a medium- to fine-grained quartzite from Naisiusiu. The polymineralic assemblage including biotite, Cr-bearing rutile, albite, and tschermakite are unique to this outcrop.
Variety 11 is a coarse- to fine-grained quartzite from Naisiusiu. The polymineralic assemblage including chlorite, calcite, and glauconite are unique to this outcrop.
Variety 14 is a coarse- to medium-grained alkali feldspar-bearing quartzite from Oittii. The modal percentages of quartz (85%), muscovite (10–15%), and alkali feldspar (~1–5%) are unique on a local scale. Similar modal percentages of quartz, muscovite, and alkali feldspar can also be found in Variety 3 from the Gol Mountains.
Variety 16 is a fine-grained staurolite-kyanite-bearing quartzite that was found in secondary position at Kelogi (
Quartzite varieties.
Endonyo Osunyai | Endonyo Osunyai 1 | Coarse | 1 | W3 |
Endonyo Osunyai 2 | Coarse | 1 | W3 | |
Endonyo Osunyai 4A | Coarse | 2 | GR2 | |
Endonyo Osunyai 4B | Coarse | 2 | GR2 | |
Gol Mountains | DDD1 | Coarse | 3 | GR2 |
PPP1 | Medium | 4 | W3 | |
RRR1 | Coarse | 4 | G1 | |
SSS1 | Coarse-medium | 4 | GR2 | |
Naibor Soit Kubwa | Naibor Soit Kubwa 27 | Coarse-fine | 5 | R3 |
Naibor Soit Kubwa 6 | Medium | 6 | GR1 | |
Naibor Soit Kubwa 32 | Coarse-medium | 6 | GR1 | |
Naibor Soit Kubwa N042 | Coarse | 7 | R3 | |
Naibor Soit Kubwa E039 | Coarse | 7 | W1 | |
Naibor Soit Kubwa S06 | Coarse | 7 | W3 | |
Naibor Soit Kubwa 1 | Medium | 7 | R3 | |
Naibor Soit Kubwa 2 | Medium | 7 | W3 | |
Naibor Soit Kubwa 8 | Coarse | 7 | R3 | |
Naibor Soit Kubwa 11 | Coarse | 7 | W3 | |
Naibor Soit Kubwa 13 | Coarse | 7 | R3 | |
Naibor Soit Kubwa 14 | Coarse | 7 | W2 | |
Naibor Soit Kubwa 24 | Coarse-fine | 7 | W2 | |
Naibor Soit Kubwa 31 | Coarse | 7 | G1 | |
Naibor Soit Kubwa 33 | Coarse | 7 | GR1 | |
Naibor Soit Ndogo | Naibor Soit Ndogo 13 | Coarse | 8 | W2 |
Naibor Soit Ndogo 14 | Coarse | 8 | G1 | |
Naibor Soit Ndogo 6A | Coarse | 9 | GR1 | |
Naibor Soit Ndogo 6B | Coarse | 9 | GR1 | |
Naibor Soit Ndogo 8 | Coarse | 9 | W3 | |
Naibor Soit Ndogo 15 | Coarse | 9 | W3 | |
Naisiusiu | Naisiusiu 4 | Medium-fine | 10 | GR2 |
Naisiusiu 7 | Coarse-fine | 11 | GR1 | |
Naisiusiu 9 | Medium | 12 | W4 | |
Naisiusiu 13 | Coarse-medium | 12 | GR1 | |
Naisiusiu 14 | Coarse-fine | 12 | W3 | |
Oittii | Oittii 1A | Medium | 13 | GR2 |
Oittii 1B | Medium | 13 | GR2 | |
Oittii 4 | Coarse-fine | 13 | GR2 | |
Oittii 3 | Coarse-medium | 14 | W4 | |
Oittii 5A | Medium | 14 | GR2 | |
Oittii 5B | Medium | 14 | GR2 | |
Granite Falls | Granite Falls 4A | Medium-fine | 15 | n/a |
Granite Falls 4B | Medium-fine | 15 | n/a | |
Kelogi | Kelogi 9 | Fine | 16 | n/a |
Although quartzitic outcrops adjacent to Oldupai have similar mineral facies (
All seven intra-outcrop varieties are differentiable from one another (
Variety 1 is a medium-grained meta-monzo-granite from the Gol Mountains. The presence of rutile allows for its differentiation from Variety 2 which is from the same outcrop. The modal percentages of quartz (45%), alkali feldspar (40%), and the absence of muscovite and hornblende allow for its differentiation from all other varieties.
Variety 2 is a medium- to fine-grained meta-quartz-rich granitoid from the Gol Mountains. The modal percentage of hornblende (6%) relative to quartz (60%) and alkali feldspar (20%) allow for its differentiation from all other varieties.
Variety 3 is a medium-to fine-grained meta-quartz-rich granitoid from the Gol Mountains. The modal percentages of quartz (70%) and biotite (10%) allow for its differentiation from all other varieties.
Variety 4 is a medium- to fine-grained granite gneiss from Granite Falls. The modal percentages of muscovite (5–8%) allow for its differentiation from all other varieties.
Variety 5 is a medium-grained aegirine-bearing granite gneiss from Kelogi. The modal percentages of aegirine (20%) and plagioclase (12–15%) allow for its differentiation from Variety 6, also from Kelogi, and from all other varieties.
Variety 6 is a medium- to fine-grained granite gneiss from Kelogi. The polyminerallic assemblage including titanite and zircon, and the modal percentages of plagioclase (25%), quartz (25%), and hornblende (20%) allow for its differentiation from all other varieties.
Variety 7 is a meta-syeno-granite from Naisiusiu. The modal percentages of opaque crystals (7%), biotite (2%), and hornblende (1%) allow for its differentiation from all other varieties.
Meta-granite varieties.
Gol Mountains | JJJ1 | Medium | 1 |
KKK1 | Medium-fine | 2 | |
TTT1 | Fine | 3 | |
UUU1 | Medium-fine | 3 | |
Granite Falls | Granite Falls 1A | Medium-fine | 4 |
Granite Falls 1B | Medium-fine | 4 | |
Granite Falls 2 | Medium-fine | 4 | |
Kelogi | Kelogi 1 | Medium | 5 |
Kelogi 3 | Medium | 5 | |
Kelogi 10 | Medium-fine | 6 | |
Naisiusiu | Naisiusiu 3 | Medium-fine | 7 |
Despite the fact that meta-granitic outcrops in the greater Oldupai region have similar mineral facies (
While not all known metamorphic, igneous, or sedimentary sources/outcrops have been characterized in this study (
Fuchsitic quartzites are unique to Naibor Soit Kubwa and Naibor Soit Ndogo (see
The discovery of hornblende granofels lithologies recovered in secondary position south of Olongojoo (
In this study, we synthesized existing descriptions with new petrographic data from several outcrops near Oldupai Gorge. By characterizing the range and variability of lithic raw materials that were available to Pleistocene hominins, we have demonstrated that there are unique mineralogical identifiers even among similar lithologies. More specifically, the comparative analyses of quartzites reveal as many as six distinguishable varieties with unique mineral assemblages, and two outcrops share fuchsitic quartzites (Variety 6/8). The identification of these mineralogically defined petrographic varieties (
All datasets for this study are included in the article and the
A preprint of this article is available with the Open Science Framework (
JF, MS, RN, PB, SC, PD, SH, and JM contributed to the conception, design, implementation, and funding of this study. JF, MS, JI, MI, FL, PL, AM, RP, and LT carried out field data collection. JF, MS, RN, CD, and RM analyzed the data. JF, MS, RN, PD, and JM wrote the manuscript. All authors revised the manuscript and approved the submitted version.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
JF acknowledges that the datasets analyzed for this study and portions of this manuscript were originally presented in the form of a Master's Thesis at the University of Calgary (Favreau,
The Supplementary Material for this article can be found online at: