Kurt Hollocher

Behavioral effects of chronic exposure to low levels of lead in Drosophila melanogaster.

Through human activity lead has become a serious environmental neurotoxin, known to affect activity levels, attention and both sensory and cognitive function in children. Study of lead would be facilitated by having a model system that could be manipulated easily and quickly. We find Drosophila melanogaster ideal as such, and we have been studying effects of lead on courtship, fecundity and locomotor activity. We raised Canton-S flies from eggs to adult day 6-7 on medium made with lead acetate solution (2-100 microgram/g), or with distilled water, and we measured adult body lead burdens by means of Inductively Coupled Plasma Mass Spectrometry (ICP-MS). To measure courtship effectiveness, five virgin females and five virgin males were transferred into an empty vial and the number of females that mated within 20min was recorded. To measure fecundity, all adult offspring from eggs produced by one female within 12 days of mating were counted. To measure locomotor activity, individual flies were transferred to a grid-labeled petri dish and the number of lines crossed in 30s was counted. The number of females mating within 20min was increased significantly by exposure to 2 or 8 microgram/g lead, and was decreased significantly by exposure to 20 or 50 microgram/g lead. Fecundity was increased significantly by exposure to 2 microgram/g lead, but was unaffected by exposure to 20 microgram/g lead. Locomotor activity was consistently higher for males than for females, and was significantly reduced only by exposure to 50 microgram/g lead, and then only for males. We thus defined for Drosophila a lowest observable effect level (LOEL) of 2 microgram/g lead, which is considerably lower than the doses shown previously to affect this animal. The dose-response curve was biphasic for the number of females mating within 20min, an example of hormesis, a non-linear response that has been reported for low levels of stressors as diverse as pollutants and radiation. We hope from further studies with Drosophila to understand better how lead affects the developing nervous system, and thus ultimately its effects on children.

Multigenerational epigenetic inheritance in humans: DNA methylation changes associated with maternal exposure to lead can be transmitted to the grandchildren.

We report that the DNA methylation profile of a child’s neonatal whole blood can be significantly influenced by his or her mother’s neonatal blood lead levels (BLL). We recruited 35 mother-infant pairs in Detroit and measured the whole blood lead (Pb) levels and DNA methylation levels at over 450,000 loci from current blood and neonatal blood from both the mother and the child. We found that mothers with high neonatal BLL correlate with altered DNA methylation at 564 loci in their children’s neonatal blood. Our results suggest that Pb exposure during pregnancy affects the DNA methylation status of the fetal germ cells, which leads to altered DNA methylation in grandchildren’s neonatal dried blood spots. This is the first demonstration that an environmental exposure in pregnant mothers can have an epigenetic effect on the DNA methylation pattern in the grandchildren.

Bacterial Residues in Coprolite of Herbivorous Dinosaurs: Role of Bacteria in Mineralization of Feces

Abstract The Cretaceous Two Medicine Formation of northwestern Montana has yielded blocky, calcareous coprolites that contain abundant fragments of conifer wood and were produced by large herbivorous dinosaurs. The coprolites are generally dark gray to black in color due to a dark substance confined chiefly within what originally were the capillaries of tracheid and ray cells of xylem. This substance is a kerogen that consists in part of thin-walled vesicles 0.1–1.3 μm in diameter. Pyrolysis products of this kerogen are diagnostic of a bacterial origin with a possible contribution from terrestrial plants. The vesicular component is interpreted as the residue of bacterial cells, whereas a second filamentous component, closely associated with the vesicles, may be the residue of an extracellular binding material, such as glycocalyx. At least two episodes of calcification of the coprolite are recognized by manganous cathodoluminescence. The earlier of these infilled the capillary channels of the conifer fragments. Wood cell walls, voids, cracks, and small burrows were filled during the later episode. Microprobe data confirm these results and show that phosphate is sequestered in the capillaries. These observations suggest that bacteria within the capillaries induced initial mineralization of the coprolite, and, in so doing, created barriers that protected organic residues from subsequent destruction. Early onset of mineralization is consistent with the degree of preservation of woody xylem found in the coprolites.

A phosphatic coprolite lacking diagenetic permineralization from the Upper Cretaceous Hell Creek Formation, northeastern Montana: Importance of dietary calcium phosphate in preservation

Abstract A single, low-density (1.58 g/cm3), phosphatic coprolite recovered from a fluvial Triceratops site in the Upper Cretaceous Hell Creek Formation of eastern Montana contains small quantities of minute bone or tooth fragments, kerogenized plant residues (pollen, spores, sporangia, and cuticle), hyphae of probable fungal origin, and small detrital mineral grains in a fine-grained, highly porous matrix. Roughly 30% of the matrix, composed almost entirely of microcrystalline francolite (carbonate-fluorapatite), is composed of thin-walled vesicles of roughly spherical shape, 0.5–3 µm in diameter. These vesicles are interpreted as mineral pseudomorphs of organic particles, probably including fecal bacteria, existing in the original scat. This structurally well-preserved coprolite is likely derived from the scat of a bone-digesting carnivorous animal, contains much or all of the autochthonous apatite of the original scat, and lacks permineralization that commonly produces a densely lithified object of low porosity. This is the first detailed description of a coprolite of this type from Mesozoic fluvial deposits. This evidence supports the view that dietary calcium phosphate could precipitate rapidly in the scat of ancient carnivorous animals, providing the structural strength to allow preservation of internal organic forms in great detail.

Geochemistry of amphibolite-facies volcanics and gabbros of the støren nappe in extensions west and southwest of Trondheim, Western Gneiss Region, Norway: a key to correlations and paleotectonic settings

The Upper Allochthon of the Scandinavian Caledonides is composed of thrust slices of a variety of metamorphosed volcanic, plutonic, and sedimentary rocks. The rocks are largely interpreted to have been formed in Cambrian to Ordovician oceanic to peri-continental arc environments that were thrust onto Baltica during the Silurian-Devonian Scandian Orogeny. We review the literature on Upper Allochthon igneous rock geochemistry broadly. We also present 87 new analyses of metamorphosed igneous rocks taken from the Surnadal and Moldefjord synforms and the Rissa area in the northern part of the Western Gneiss Region, where highly deformed Upper Allochthon rocks are preserved. Here the Upper Allochthon is dominated by basaltic volcanics and gabbros with sparse intermediate and felsic rocks. Most of the mafic rocks are transitional between MORB- and arc-type compositions in tectonic discriminant diagrams and for REE and multi-element patterns. We present two new discriminant diagrams to illustrate this subtle transitional characteristic. We interpret these volcanics as having been erupted in a mature back-arc basin environment where mantle sources for the magmas were only slightly influenced by the subduction zone component from an adjacent arc. Another set of mafic volcanic rocks, coming only from the Storås and Rissa areas, were extruded in an oceanic arc-type environment. These two geochemical types, back-arc and oceanic-arc, are closely matched by Støren Group ophiolites in the Trondheim Region which are dominated by basaltic volcanics and gabbros and generally lack felsic igneous and sedimentary rocks. Felsic igneous rocks, sedimentary rocks, and calc-alkaline and alkaline volcanics are more abundant in stratigraphically younger units of the Upper Allochthon, including the Lower and Upper Hovin Groups. We correlate the Upper Allochthon igneous rocks in the Moldefjord and Surnadal synforms and the Rissa area with ophiolites of the Støren Group. Early oceanic-arc and back-arc volcanic rocks, followed by more calc-alkaline to alkaline volcanics, are the dominant pattern for ophiolite sequences in the rest of the Upper Allochthon of the Scandinavian Caledonides. We envisage a paleotectonic scenario in which a Late Cambrian to Tremadocian, oceanic-arc system developed above a subduction zone dipping oceanward from a microcontinent that had earlier rifted away from Baltica or possibly Ganderia. The ophiolitic and primitive arc rocks are inferred to have been obducted in Late Tremadocian–Early Floian time upon epicontinental rocks flanking the microcontinent, which was then drifting rapidly across the Iapetus Ocean approaching Laurentia. A new arc and marginal basin developed, following a subduction polarity reversal, with the Dapingian-Darriwilian sedimentary infill being replete with Laurentian faunas, and locally punctuated by calc-alkaline volcanics and dikes, with fringing reefal limestones. The entire volcano-sedimentary assemblage was later affected by Scandian (Silurian–Early Devonian) orogenesis during emplacement of the major nappes onto the Baltoscandian margin.

The Neoproterozoic Ottfjället dike swarm of the Middle Allochthon, traced geochemically into the Scandian Hinterland, Western Gneiss Region, Norway

The Ottfjället swarm of Late Neoproterozoic mafic dikes, cutting Neoproterozoic sandstones, became a key, 30 years ago, to the tectonics of the Scandian Caledonides. The sandstones were deposited in basins related to opening of Iapetus, and intruded by dikes in distal parts of the Baltoscandian margin close to the developing spreading axis. The sandstones and underlying basement rocks were transported, from west of the present Norwegian coast, to as far east as western Sweden during the Silurian-Devonian Scandian Orogeny. The sandstones with dikes make up the Särv Nappe, up to 2 km thick in Sweden, and the quartzites and amphibolites of the Sætra and equivalent nappes in Norway. These form the upper part of the Middle Allochthon. The lower part of the Middle Allochthon includes Middle Proterozoic basement gneisses and rapakivi granites, containing mafic rocks in some places. The dike-bearing quartzite is a key unit due to contrast with similar rocks lacking dikes at lower tectonic levels derived from inboard parts of Baltica. The Sætra Nappe and equivalents are well constrained on lithotectonic grounds in Norway at Oppdal, Leksdal, and Orkanger. It was also suspected to occur in deep, narrow synclines in the Western Gneiss Region where interlayered feldspathic quartzite and amphibolite are in correct tectonostratigraphic sequence, locally with a total thickness of only 1 to 3 m, and locally with dikes converted to eclogite. To test correlations, 127 samples of mafic rocks were collected from 14 areas west and southwest of Trondheimsfjord into the Western Gneiss region toward Ålesund. Samples include mafic rocks in quartzites and others, some clearly dikes, from the underlying 1190 Ma rapakivi granite/augen gneiss of the Risberget Nappe and adjacent basement gneisses. Typical Sætra dikes in the Oppdal quarries, and mafic rocks from other quartzites and related rocks, have Lan/Smn ratios of 1.0 to 1.8, and Nb/La ratios of 0.8 to 1.4 (Oppdal group). Most REE patterns are moderately LREE-enriched with no or very small, mostly negative, Eu anomalies. All have similar multi-element patterns typically with small positive P anomalies, negative Zr-Hf anomalies and an absence of Nb-Ta anomalies, showing that the dikes are unrelated to arcs and have no notable continental crust component. A subset of Sætra, Risberget, and basement dikes is distinguished by higher Lan/Smn ratios of 1.8 to 2.5, but otherwise has very similar characteristics (Ystland Group). These data support correlation of the Sætra Nappe quartzite and dikes into highly deformed parts of the Western Gneiss Region and correlation of nearby dike-rich parts of basement gneiss with the Middle Allochthon. One sample in quartzite at Ura, at an unusual tectonostratigraphic position, has Lan/Smn = 0.7, Nb/La = 0.6, and a multi-element pattern different from Sætra dikes, suggesting it is unrelated to the Ottfjället dikes. Non-Sætra-like amphibolites also occur in the Risberget Nappe, and have Lan/Smn ratios of 1.4 to 3, all Nb/La ratios <0.6, and multi-element patterns with sharp negative anomalies for Nb-Ta, P, Zr-Hf and Ti. These are probably Mesoproterozoic magmas and cumulates emplaced into the rapakivi granite protolith of the augen gneiss. Data from this and earlier studies of correlative nappes in adjacent regions can be geographically partitioned into transitional MORB-like compositions with relatively low LREE enrichment to the north and south, and more LREE-enriched alkaline compositions concentrated at about the latitude of northern Trondheimsfjord (∼64°N). We interpret the zone of alkaline rocks to have been influenced by a nearby source of hot-spot-related enriched mantle during Late Neoproterozoic rifting of Baltica from Rodinia, with striking geochemical and spatial parallels to the modern Mid-Atlantic region.

Carnivore Coprolites from the Upper Triassic Ischigualasto Formation, Argentina: Chemistry, Mineralogy, and Evidence for Rapid Initial Mineralization

Abstract Coprolites were collected 74 m above the base of the Upper Triassic Ischigualasto Formation of northwestern Argentina and their chemistry, mineralogy, and textures were studied to infer their biological source and taphonomy. They were found to contain a few fragments of bone and much crystalline apatite, and so can be assigned to carnivores able to digest bone. Primary minerals derived from endogenous materials were apatite and pyrite, and secondary minerals derived from ground water were chiefly calcite and glauconite in one coprolite and glauconite in another. Primary apatite, presumed originally to have been mostly dahllite (a carbonate hydroxyapatite) precipitated from digested bone, was converted to francolite (a carbonate fluorapatite) during diagenesis through the introduction of fluoride from ground water. The chemistry, mineralogy, and structure of the coprolites suggest an early onset of mineralization, early anaerobic burial, and a recent anaerobic-to-aerobic transition during weathering. The chemistry of the coprolites is consistent with the stratigraphic identification of the coprolite horizon as an ancient flood plain.

Progressive reactions and melting in the Acadian metamorphic high of central Massachusetts and southwestern New Hampshire, USA

The purpose of this chapter is to describe briefly and summarize changes in the mineral assemblages and mineral compositions that are observed in various rock types along the metamorphic field gradient in the metamorphic high of central Massachusetts and southwestern New Hampshire, USA. The progressive metamorphism of rocks of basaltic composition is discussed here more extensively than for rocks of common pelitic compositions, because detailed descriptions of the progressive metamorphism of basaltic rocks at these metamorphic conditions are less common. This chapter is aimed, in part, at non-petrologists and postgraduate students. As a consequence, some basic subjects are discussed, including some general comments concerning P-T-t (pressure-temperature-time) paths and metamorphic field gradients. However, some aspects should interest petrologists looking for meatier topics.

Orogenic to postorogenic (1.20–1.15 Ga) magmatism in the Adirondack Lowlands and Frontenac terrane, southern Grenville Province, USA and Canada

Magmatism in the southern Grenville Province records a collisional and postcollisional history during the period 1.20–1.15 Ga in the Adirondack Lowlands (New York State, USA) and the Frontenac terrane (Ontario, Canada). The 1.20 Ga bimodal Antwerp-Rossie suite of the Adirondack Lowlands was produced by subduction in the Trans-Adirondack backarc basin. This was followed by intrusion of the 1.18 Ga alkalic to calc-alkalic Hermon granite, which may have been generated by melting of metasomatized mantle during collision of the Adirondack Lowlands and Frontenac terrane during the Shawinigan orogeny. The Hyde School gneiss plutons intruded the Adirondack Lowlands at 1.17 Ga, and Rockport granite intruded into the Adirondack Lowlands and Frontenac terrane, stitching the Black Lake shear zone, which marks the boundary between these terranes. Subsequent extensional collapse and lithospheric delamination caused voluminous anorthosite-mangerite-charnockite-granite plutonism. In the Frontenac terrane, this event is represented by the 1.18–1.15 Ga Frontenac suite, which is composed predominately of ferroan granitoids produced from melting of the lower crust by underplating mafic magmas. The Edwardsville, Honey Hill, and Beaver Creek plutons are newly recognized members of this suite in the Adirondack Lowlands. High oxygen isotope ratios of this suite in the central Frontenac terrane and western Adirondack Lowlands point to the presence of underthrust altered oceanic rocks in the lower crust. Oxygen isotopes of the Frontenac suite in both terranes preclude its derivation from mantle melts alone.

Geochemistry of the metamorphosed Ordovician Taconian Magmatic Arc, Bronson Hill anticlinorium, western New England

The Bronson Hill anticlinorium (BHA) in western New England is a north- to northeast-trending belt of gneiss domes containing a metamorphosed stratified sequence of Ordovician, Silurian, and Devonian sedimentary and volcanic rocks. These overlie mostly late Ordovician intrusive igneous rocks. The intrusive rocks, exposed in the dome centers, are dominated by felsic gneisses of tonalitic to granitic compositions. They are the exposed parts of a composite batholith that developed along the axis of the Taconian volcanic arc. The Fourmile Gneiss of the Pelham dome, and the Monson Gneiss of the Monson dome, covered in most detail here, are calc-alkaline, dominantly tonalitic to granodioritic gneisses having 61–78% SiO2. These are divided into two geochemical groups. The most abundant rocks have low Sr (∼50–200 ppm), high Y (∼10–50 ppm), low Al2O3, high FeOt, commonly negative Eu anomalies, and have flat to somewhat concave upward MREE and HREE patterns. These rocks were probably derived from melting of plagioclase–pyroxene–amphibole granulites in the deep crust. Rocks of the subordinate high-Sr group are similar in composition to adakites and have high Sr (∼300–600 ppm), low Y (∼1–13 ppm), higher Al2O3, lower FeOt, commonly no Eu anomalies, and are strongly depleted in HREE. These rocks were probably derived from a pyroxene–amphibole–garnet ± plagioclase source at higher pressure. Amphibolites are low in abundance in the Fourmile and Monson Gneisses. Most are a low-Nb type (<6 ppm Nb), compositionally similar to typical calc-alkaline island arc basalts. These were probably derived by melting of spinel lherzolite in the mantle wedge under the arc. Gabbroic anorthosite and ultramafic rocks also occur in the Monson dome and appear to be cumulates from magmas similar to the low-Nb amphibolites. A high-Nb (6–12 ppm) amphibolite group was identified and is unique to the Monson Gneiss. These rocks are transitional between calc-alkaline and alkaline basalts, are strongly LREE-enriched (La is 46–440 times chondrite), are enriched in strongly incompatible elements, and two of seven samples have normative nepheline. A broader survey of available analytical data from BHA felsic gneisses shows that gneiss compositions vary from dominantly tonalitic and granodioritic in the southern BHA to dominantly granitic from the Croydon and Mascoma domes (west-central New Hampshire) northward. This variation suggests that the southern part of the arc exposed in the BHA was based on mafic crust, whereas the northern part was based on intermediate to felsic crust. Examination of radiometric dates of Taconian igneous rocks, and biostratigraphic constraints in the Taconic allochthons and in the Taconian foreland, are consistent with a model in which the BHA gneisses are the youngest igneous components of the Taconian arc proper. Collision of this composite arc with Laurentia reached a conclusion in the latest Caradoc or Ashgill of the late Ordovician or in the very earliest Silurian. Younger plutons continuing into the Silurian (e.g., Highlandcroft in part) may be related to magmas generated during post-collision delamination or detachment of the subducted Iapetus oceanic slab.