https://www.utdallas.edu/~rjstern/egypt/PDFs/Cenozoic%20Red%20Sea/BosworthRedSeaJAES05.pdf

The Red Sea and Gulf of Aden Basins

A continuous record of atmospheric lead since 12,370 carbon-14 years before the present (14C yr BP) is preserved in a Swiss peat bog. Enhanced fluxes caused by climate changes reached their maxima 10,590 14C yr BP (Younger Dryas) and 823014C yr BP. Soil erosion caused by forest clearing and agricultural tillage increased lead deposition after 532014C yr BP. Increasing lead/scandium and decreasing lead-206/lead-207 beginning 3000 14C yr BP indicate the beginning of lead pollution from mining and smelting, and anthropogenic sources have dominated lead emissions ever since. The greatest lead flux (15.7 milligrams per square meter per year in A.D. 1979) was 1570 times the natural, background value (0.01 milligram per square meter per year from 8030 to 5320 14C yr BP).

https://science.sciencemag.org/content/sci/281/5383/1635.full.pdf

History of Atmospheric Lead Deposition Since 12,370 14C yr BP from a Peat Bog, Jura Mountains, Switzerland

C yr BP indicate the beginningof lead pollution from mining and smelting, and anthropogenic sources havedominated lead emissions ever since. The greatest lead sux (15.7 milligrams persquare meter per year in A.D. 1979) was 1570 times the natural, backgroundvalue (0.01 milligram per square meter per year from 8030 to 5320

History of Atmospheric Lead Deposition Since 12,370 14 Cy r BP from a Peat Bog, Jura Mountains, Switzerland

Principles of Isotope Geology

This paper is included in the Special Publication entitled 'Lyell: the past is the key to the present', edited by D.J. Blundell and A.C. Scott. This paper presents new ideas on the Early Palaeozoic geography and tectonic history of the Iapetus Ocean involved in the formation of the northern Appalachian-British Caledonide Orogen. Based on an extensive compilation of data along the length of the orogen, particularly using well-preserved relationships in Newfoundland as a template, we show that this orogen may have experienced a very complicated tectonic evolution that resembles parts of the present west and southwest Pacific Ocean in its tectonic complexities. Closure of the west and southwest Pacific Ocean by forward modelling of the oblique collision between Australia and Asia shows that transpressional flattening and non-coaxial strain during terminal collision may impose a deceptively simple linearity and zonation to the resultant orogen and, hence, may produce a linear orogen like the Appalachian-Caledonian Belt. Oceanic elements may preserve along-strike coherency for up to several thousands of kilometres, but excision and strike-slip duplication, as a result of oblique convergence and terminal collisional processes, is expected to obscure elucidation of the intricacies of their accretion and collisional processes. Applying these lessons to the northern Appalachian-Caledonian belt, we rely principally on critical relationships preserved in different parts of the orogen to constrain tectonic models of kinematically-related rock assemblages. The rift-drift transition, and opening of the Iapetus Ocean took place between c.590-550 Ma. Opening of Iapetus was temporally and spatially related to final closure of the Brazilide Ocean and amalgamation of Gondwanaland. During the Early Ordovician, the Laurentian margin experienced obduction of young, supra-subduction-zone oceanic lithosphere along the length of the northern Appalachian-British Caledonian Belt. Remnants of this lithosphere are best preserved in western Newfoundland and are referred to as the Baie Verte Oceanic Tract. Convergence between Laurentia and the Baie Verte Oceanic Tract was probably dextrally oblique. Slab break-off and a subsequent subduction polarity reversal produced a continental magmatic arc, the Notre Dame Arc, on the edge of the composite Laurentian margin. The Notre Dame Arc was mainly active during the late Tremadoc-Caradoc interval and was flanked by a southeast- or south-facing accretionary complex, the Annieopsquotch Accretionary Tract. Southerly drift of Laurentia to intermediate latitudes of c.20-25°S was associated with the compressive (Andean) nature of the arc and the accompanying backthrusting of the already-accreted Baie Verte Oceanic Tract further onto the Laurentian foreland. Equivalents of the Notre Dame Arc and its forearc elements in the British Isles have been preserved as independent slices in the Midland Valley and possibly the Northern Belt of the Southern Uplands. During the late Tremadoc (c.485 Ma), the passive margin on the eastern side of Iapetus also experienced obduction of primitive oceanic arc lithosphere. This arc is referred to as the Penobscot Arc. The eastern passive margin was built upon a Gondwanan fragment (Ganderia) that rifted off Amazonia during the Early Ordovician and probably travelled together with the Avalonian terranes as one microcontinent. The departure of Ganderia and Avalonia from Gondwana opened the Rheic Ocean. Equivalents of the Penobscot Arc may be preserved in New Brunswick and Maine, Leinster in eastern Ireland, and Anglesey in Wales. An arc-polarity reversal along the Ganderian margin after the soft Penobscot collision produced a new arc: the west-facing Popelogan-Victoria Arc, which probably formed a continuous arc system with the Bronson Hill Arc in New England. The Popelogan-Victoria Arc transgressed from a continental to an oceanic substrate from southern to northeastern Newfoundland. Rapid roll-back rifted the Popelogan-Victoria Arc away from Ganderia during the late Arenig (c.473 Ma) and opened a wide back-arc basin; the Tetagouche-Exploits back-arc basin. The Popelogan-Victoria Arc was accreted sinistrally oblique to the Notre Dame Arc and, by implication, Laurentia during the Late Ordovician. After accretion, the northwestward-dipping subduction zone stepped eastwards into the Tetagouche-Exploits back-arc basin.

The Cambrian-Silurian tectonic evolution of the northern Appalachians and British Caledonides: history of a complex, west and southwest Pacific-type segment of Iapetus

The paleoproterozoic Ghanaian province: Geodynamic model and ore controls, including regional stress modeling

The West Central African belt: a model of 2.5–2.0Ga accretion and two-phase orogenic evolution

The origin of atmospheric particles in Paris: a view through carbon and lead isotopes

Proterozoic tectonism of the Arabian Shield

We report here a newly developed method for measurement of Li isotopes by use of multi-collector ICP-MS (Neptune) allowing rapid and high precision determination of Li isotope ratios at low levels of lithium (15–20 ng). The lithium reference sample solution IRMM-016 was analysed over a period of ten months with an external reproducibility of 0.24% (2s, n = 52). Chemical separation of Li from matrix was performed on the seawater sample IRMM BCR-403, for which a mean δ7Li value of + 31.0 ± 0.1 % (2s/√n, n = 31) was obtained. This mean value is in good agreement with those previously published for other seawater samples. BCR-403 seawater being readily available, we propose that this seawater sample be used as a reference sample for Li isotope measurements.

Catherine Guerrot

Papers

The paleoproterozoic Ghanaian province: Geodynamic model and ore controls, including regional stress modeling

The West Central African belt: a model of 2.5–2.0Ga accretion and two-phase orogenic evolution

The origin of atmospheric particles in Paris: a view through carbon and lead isotopes

Proterozoic tectonism of the Arabian Shield

Accurate and High-Precision Measurement of Lithium Isotopes in Two Reference Materials by MC-ICP-MS