Michael W. Milner

Mineral and chemical analyses of soils eaten by humans in Indonesia.

Five Javanese soil samples, including three earths eaten by humans as therapeutic medicine, were analyzed for their physical, mineral and chemical properties along with suitable control samples (not eaten). The eaten soils have a high content of hydrated halloysite and kaolinite, that is, clay minerals that are pseudoforms of the pharmaceutical Kaopectate™. Along with hydrated halloysite in a ratio of nearly 1:1, the expandable clay mineral smectite is also present, but in much greater quantity than is usually found in Kaopectate™. Among the chemical elements that may act as a stimulus for geophagy, only Na, Mn, K and S are possible candidates driving this behavior. Sodium is inherent in the minerals derived from the volcanic bedrock; and it is present in a form other than NaCl. Iron, which is often higher in soils eaten by both human and nonhuman primates, and has therefore been regarded in the past as a possible stimulus for geophagy, is relatively high in these soils, but does not have a higher concentration in the eaten soils relative to the uneaten soils in this group of samples. Cobalt and chromium, two important trace elements in human nutrition and diet, are marginally but not markedly higher in the eaten samples. The eaten soils in all cases have predominantly higher levels of 1:1 clay minerals than the 2:1 minerals which may predominate in some of the control soils, which some studies have associated with health problems. Soils can adsorb dietary toxins, present in the plant diet or those produced by microorganisms. Taking the toxic alkaloids quinine, atropine, sparteine, and lupanine as examples, it is evident that soils from Ampo (southern Java) have a very good adsorptive capacity, comparable to that of coal or charcoal. Other Javanese soils also adsorb these toxins, but to a lesser degree.

Chemistry, mineralogy and microbiology of termite mound soil eaten by the chimpanzees of the Mahale Mountains, Western Tanzania

Subsamples of termite mound soil used by chimpanzees for geophagy, and topsoil never ingested by them, from the forest floor in the Mahale Mountains National Park, Tanzania, were analysed to determine the possible stimulus or stimuli for geophagy. The ingested samples have a dominant clay texture equivalent to a claystone, whereas the control samples are predominantly sandy clay loam or sandy loam, which indicates that particle size plays a significant role in soil selection for this behaviour. One potential function of the clays is to bind and adsorb toxins. Although both termite mound and control samples have similar alkaloid-binding capacities, they are in every case very high, with the majority of the samples being above 80%. The clay size material (<2 μm) contains metahalloysite and halloysite, the latter a hydrated aluminosilicate (Al 2 Si 2 O 4 -nH 2 O), present in the majority of both the termite mound soil and control soil samples. Metahalloysite, one of the principal ingredients found in the pharmaceutical Kaopectate is used to treat minor gastric ailments in humans. The soils commonly ingested could also function as antacids, as over half had pH values between 7.2 and 8.6. The mean concentrations of the majority of elements measured were greater in the termite mound soils than in the control soils. The termite mound soils had more filamentous bacteria, whereas the control soils contained greater numbers of unicellular bacteria and fungi.

Analysis of geophagy soils in Kibale Forest, Uganda

Four soil samples from the Kibale Forest, Uganda, representative of material regularly ingested by chimpanzees, were studied for their mineral, chemical, and geochemical composition. These geophagy soils have a high content of metahalloysite, a partially hydrated clay mineral that may act much like the pharmaceutical Kaopectate™. Among the elements that may act as a stimulus or stimuli for geophagy behavior, only iron is very high (total iron ranges from 6% to 17%); other possibilities such as calcium, chromium, cobalt, bromine, and iodine are either relatively low or are below their detection limits. Chlorine is below detection limits which eliminates sodium chloride as a possible stimulus. Depending on relative availability in the gut, iron offers the most likely chemical stimulus for geophagy and given the mineral composition of the samples, metahalloysite is the most likely mineral stimulus. Iron may play a role in replenishing hemoglobin which would be important in chimpanzee physiology at high elevations near the flanks of the Ruwenzori Mountains. Metahalloysite, which in this case exists in a relatively pure crystalline form, may well act to quell symptoms of diarrhea and act similarly to Kaopectate™. Organic chemical analyses indicate only traces of organic matter and no humic acids in the K14-E14 sample.

Paleopedology of Middle Wisconsin/Weichselian paleosols in the Mérida Andes, Venezuela

Abstract Buried Spodosols (podzols) within a thick lithostratigraphic section in the northern Venezuelan Andes are interbedded with tills and a succession of multicyclic lacustrine clays, silts and sands from the early and middle stades of the Wisconsinan/Weichselian Glaciation. The peats, dated by AMS radiocarbon, allow calculations of the time required for pedogenesis. These Spodosols were studied to determine compositional changes from initial to full soil development. During lake low water stands, peats of variable thickness developed, along with soils belonging to the Spodosol order. On a relative time scale, the initial stage of soil genesis produced peat with a weathered mineral zone (Bs)—initial spodic horizon of a few centimeters thickness. With a longer time for soil genesis of a few centuries, a thin Spodosol developed with an E/Bs horizon sequence. With still longer time spans of a few thousand years, between 55 and 60 ka, more mature Spodosols with E/Bs/Cox/Cu profiles formed beneath very thick peat in conjunction with groundwater fluctuations. The lowermost peat (VII) in the section varies from 15 to 26.5 cm in thickness. The paleosols are sandy, with little evidence of either clay transformations, or silt accretion from airfall influx, apparent from the particle size analysis. XRD analysis of the clay fraction shows minor weathering of illite to vermiculite and chlorite in the Bs horizons. Chemically extractable forms of Fe and Al show increases of both soluble and insoluble minerals from the E to the Bs horizons in the buried Spodosols, a considerably different trend compared with the surface soils (Entisols). Geochemical trace element analysis shows a moderate degree of translocation of soluble chemical elements from the E to the Bs horizons.

Mineralogical and chemical interactions of soils eaten by chimpanzees of the Mahale mountains and Gombe stream National Parks, Tanzania

Termite mound soils eaten by chimpanzees of the Mahale Mountains and Gombe National Parks, Tanzania, have mineralogical and geochemical compositions similar to many soils eaten by higher primates, but release very low levels of either toxic or nutritional inorganic elements to solution at acid pH. Comparison with control (uneaten) soils from the same areas showed lower levels of carbon and nitrogen in the eaten soils, a relationship confirmed by surface analysis. Surface analysis also revealed lower levels of iron on particle surfaces versus interiors, and higher levels of iron on ingested versus control soil particle surfaces. The soils can adsorb dietary toxins, present in the plant diet or those produced by microorganisms. Taking the toxic alkaloids quinine, atropine, sparteine, and lupanine as examples, it is evident that soils from Mahale have a very good adsorptive capacity. A new adaptive advantage of geophagy is proposed, based on the prevention of iron uptake. The behavior of the soils in vitro is consistent with the theory that geophagy has a therapeutic value for these chimpanzees.

Soils Consumed by Chimpanzees of the Kanyawara Community in the Kibale Forest, Uganda

We previously reported on a study of 4 soils that chimpanzees of the Kanyawara community in the Kibale National Park, Uganda consumed on a near-daily basis. We suggested that iron was a possible chemical stimulus in association with high quantities of Si:Al = 1:1-dominated clay minerals in the consumed material. To test our initial findings, we analyzed 18 samples from the same general area including 7 samples that the chimpanzees did not eat. Among the chemical elements, As, Au, Br, Ca, Cl, Dy, Mg, Ni, Sb, Sr, and I are below detection limits. Only Fe stands out as a potentially important nutritional element present in sufficient quantity to provide a physiological stimulus for chimpanzees living at high elevations near the flanks of the Ruwenzori Mountains. Along with Fe, metahalloysite is present in high amounts in these soils. In its pure crystalline form as a pharmaceutical grade clay mineral metahalloysite may well counteract the debilitating effects of diarrhea, with an effect similar to what is achieved with kaolinite (cf. KaopectateTM). An unexpected result, the relatively high nitrogen and carbon in the eaten samples relative to the uneaten group, indicates the chimpanzees may have a higher threshold for organic-rich material than previously believed. Contrarily, the color of the ingested material, depicts a material with less humus than in the uneaten group, a finding that is compatible with previous work reported at other geophagy sites in Africa. Of all the choices of soil available to them, the chimpanzees appear to be selecting highly homogeneous chemical natural earths with well-leached and uniform mineralogical material similar to the uneaten group, but with higher relative amounts of clay size material.

Weathering Rinds: Archives of Paleoenvironments on Mount Kenya, East Africa

Weathering-rind thicknesses on pebble- and cobble-size sediment have been used for the past half-century, at least, as an age indicator of postdepositional time following a geologic event. In mountainous terrain, rind thickness is taken as a measurement of weathering over time frames of 0.5 m.yr.; variable thicknesses are used to discriminate relative ages of glacial deposits. The effects of chemical and physical weathering that together produce rinds are only rarely considered, and most research objectives have centered on lichen alteration of clast surfaces. Recent microscopic analyses of weathering rinds on volcanic clasts of ∼70.0-ka to ∼2.0-m.yr. age produced new data on weathering products as well as unexpected incorporated biotic materials undergoing diagenesis. The question as to how much physical/mineral/chemical/biotic paleoenvironmental data might be archived in rinds is discussed. The character and classification of organic materials undergoing diagenesis are also discussed.

Geophagy by the Bonnet Macaques (Macaca radiata) of Southern India: A Preliminary Analysis

Bonnet macaques (Macaca radiata) in the Marakkanam Reserved Forest of southern India consume termitaria soils. Samples from the ingested termite mounds are compared with samples taken from the surrounding uneaten soils in an attempt to determine why the termitaria soils are eaten. Particle size, clay and primary mineral composition, geochemistry, and scanning electron microscopic analyses are used to search for a possible explanation for geophagy among the bonnet macaques. Kaolin minerals abound throughout the Marakkanam soil sample suite. But the termitaria soils are distinguished by the presence of small amounts of smectite. An abundance of kaolin minerals in combination with small amounts of smectite strongly resembles the mineralogy ofeko, a traditional African remedy for stomach ailments, and Kaopectate™, a western anti-diarrhoeal preparation. The percentage of mature leaves and fruits ofAzadirachta indica consumed by the bonnet macaques is relatively high. Plant feeding deterrents, such as, acid detergent fibre (ADF) and the inherent nature of the fruits ofAzadirachta indica, when consumed in large quantities to act as a purgative, could cause gastrointestinal upsets and diarrhoea. At Marakkanam, bonnet macaques ingest termitaria earth that would act as a pharmaceutical agent to alleviate gastrointestinal upsets and control diarrhoea.

Late Neogene volcanics and interbedded palaeosols near Mount Kenya

Abstract Two lava flows with interbedded palaeosols outcrop c. 40 km SW of Mount Kenya, near the Amboni River north of Mweiga, Kenya along the Nyeri/Thompson Falls Road, at 0°18′S; 37°48′E. These flows, overlain by loess, are principally trachyandesite and form the base of the Mount Kenya Volcanic Series which, in the early literature, is described as being of probable Miocene/Pliocene age. Here we report 39Ar/40Ar dates (c. 5.2–5.5 Ma) and reversed magnetizations which establish a Latest Miocene to Earliest Pliocene age for these flows. Weathering characteristics of palaeosols interbedded with the lavas indicate generally dry climatic conditions during the Late Miocene, punctuated with humid events during the Pliocene and Quaternary. These Late Miocene–Quaternary palaeosols depict a relatively long and complex weathering history, followed by loess deposition. The palaeosols appear to have been episodically deflated, initially in phase with the deposition of lavas when surfaces were devoid of vegetation and later during periods of climatic deterioration when wind systems intensified. Such weathering histories within palaeosol profiles are also documented on nearby Mount Kenya, where well-weathered lower palaeosol horizons developed on Matuyama-age tills are overlain by much younger less-weathered horizons developed on Brunhes-age loess. The geochronology of Late Miocene lavas reported here provides maximum ages for weathering histories of palaeosols formed in a xeric tropical highland climate.

GEOCHEMISTRY OF SPODOSOLS FORMED IN HOLOCENE TILL, NORRA STORFJALLET MASSIF, NORTHERN SWEDEN

Silt and clay size fractions of soils, from a transect of six Spodosols formed in the Norra Storfjället Massif, were analyzed by neutron activation to determine the degree to which pedogenic processes have influenced the distribution of macro, micro and trace elements. The distributions of Mg, Ca and Fe, together with Co, Cr and other trace elements in the profiles, suggest the presence of different parent materials, with A and E horizons arising from an influx of aeolian sediment. Translocation processes, both physical and chemical, occurred in the soil concentrating Fe and Br in the spodic (Bs) horizons of the profiles. The rare earth elements (REEs) are predominantly associated with the heavy mineral fraction of the soil material. The distributions of chondrite normalized REEs patterns of the profiles indicate that light rare earth element (LREE) concentrations increase with horizon depth. The depletion of LREEs in the upper soil horizons confirms the presence of material that is chemically different from that in the lower horizons, thus indicating a distinct chemical difference from the local glacial deposits.