Reconciling geodetic and geological rates of vertical crustal motion in intraplate regions

in Earth & Planetary Science Letters (2004), 221

Tectonic motion rates of individual faults and regional deformation in an intraplate setting are estimated, based on the analysis of ten yearly surveys of a regional levelling network in NE Ardenne (W ... [more ▼]

Tectonic motion rates of individual faults and regional deformation in an intraplate setting are estimated, based on the analysis of ten yearly surveys of a regional levelling network in NE Ardenne (W Europe). Owing to the frequency and number of measurement epochs, much greater than in classical comparisons of general surveys, the tectonic and near-surface components of ground motion are clearly separated. The marked temporal variability in ground motion strongly depends on the amount of precipitation fallen during the six months preceding each survey and the subsequent drying off of the subsoil at the time of the surveys. Moreover, the ground response to this influence varies from place to place, leading to high differential movements at the local scale. Taking into account the percentage of surveyed faults which moved tectonically during the time of the study, I calculate fault motion rates of 0.06^0.09 mm/yr, similar to geological rates. Moreover, the data indicate that one way for intraplate normal faults to accommodate tectonic strain aseismically is intermittent fault creep, with short episodes of a few mm displacement separated by many year-long time intervals of fault quiescence. A flexural deformation shows the superposition of a tilt event on a trend corresponding to a tilt rate of 0.16 Wrad/yr for a 2.8-km-long segment. [less ▲]

Sm-Nd signature of modern and late Quaternary sediments from the northwest North Atlantic: Implications for deep current changes since the Last Glacial Maximum

in Earth & Planetary Science Letters (1997), 146(3-4), 607-625

Nd isotopes and Sm-Nd concentrations have been investigated in the clay size fraction of surface and late Quaternary sediments of the northern North Atlantic. Four sources of Nd have been identified in ... [more ▼]

Nd isotopes and Sm-Nd concentrations have been investigated in the clay size fraction of surface and late Quaternary sediments of the northern North Atlantic. Four sources of Nd have been identified in the surface sediments: (1) a radiogenic Nd typical of the Iceland volcanism; (2) a ''Pan-African'' Nd issued from eastern Greenland; (3) a ''Variscan'' Nd derived from the Arctic Ocean; (4) an old unradiogenic Nd related to the North American Shield, In the Iceland and Irminger basins, the major sources of Nd are the Variscan Nd derived from the Arctic Ocean and the Iceland Nd, except in the western Irminger Basin where the Pan-African Nd originating from eastern Greenland is dominant and labels sedimentary supplies linked to the Denmark Strait Overflow Water, Nd derived from Icelandic volcanism is never clearly dominant, even on the Reykjanes Ridge, and the Nd derived from the American Shield becomes dominant only in the Labrador Sea, Sediments lying in the pathway of the Western Boundary Undercurrent have Nd isotopic compositions which are shifted towards more radiogenic values indicating an input of material from the eastern basins, carried by this deep current. Late Quaternary sediments were cored from the southern Greenland Rise (core 90-013-013) and eastern Labrador Rise (Orphan Knell; core 91-045-094). In core 90-013-013, epsilon Nd values during the Last Glacial Maximum are as low as -20, but subsequently rose to -9 in the modern sediments, indicating that the sedimentary material during the Last Glacial Maximum was dominated by unradiogenic Nd from the North American Shield. This may be related to a lesser outflow of the Western Boundary Undercurrent, In core 91-045-094, located along the Labrador Current trajectory, a dominant supply of North American Shield Nd is recorded, perhaps originating at least partially from the Hudson Strait, The Sm-Nd data are compatible with smectite vs. illite studies at the same sites which suggest a continuous but more modest Western Boundary Undercurrent supply during Last Glacial Maximum. [less ▲]

The short duration and anorogenic character of anorthosite magmatism: U-Pb dating of the Rogaland complex, Norway

in Earth & Planetary Science Letters (1996), 139

Trace elements and anorthosite genesis

in Earth & Planetary Science Letters (1978), 38