The Canada-Newfoundland Atlantic Accord Implementation Act: Transparency of the environmental management of the offshore oil and gas industry

This paper considers the overall outcome of a “public environmental audit” of the government management of the oil and gas offshore industry in eastern Canada. Five requests for data sets were placed using the Access to Information Act; all five requests were denied by the Canada-Newfoundland Labrador Offshore Petroleum Board. This lack of access to environmental monitoring data significantly hinders the ability of independent scientific inquiry and/or public involvement in the environmental assessment process.     

Implications of the 2011 M9.0 Tohoku Japan earthquake for the treatment of site effects in large earthquakes

Site response in Japan is characterized using thousands of surface and borehole recordings from events of moment magnitude $(\mathbf{M}) > 5.5$ collected by the KiK-net network, including the 2011 M9.0 Tohoku earthquake. Site amplification is defined by the ratio of motions at the surface to those at depth (within the borehole), corrected for the depth effect due to destructive interference using a technique based on cross-spectral ratios between surface and down-hole motions. Site effects were particularly strong at high frequencies, despite the expectation that high-frequency response may be damped by nonlinear effects. In part, the large amplitudes at high frequencies are due to the prevalence of shallow soil conditions in Japan. We searched for typical symptoms for soil nonlinearity, such as a decrease in the predominant frequency and/or amplification, using spectral ratios of weak to strong ground motions. Localized nonlinearity occurred at some recording sites, but was not pervasive. We developed a general empirical model to express site amplification for the KiK-net sites as a function of common site variables, such as the average shear-wave velocity in the uppermost 30 m ( $\text{ V}_\mathrm{S30})$ and the horizontal-to-vertical (H/V) spectral ratio. We use the model to estimate site-corrected ground-motions for the Tohoku mainshock for a reference site condition; these motions are in reasonable agreement with the predictions of some of the published ground motion prediction equations for subduction zones.     

A new shoreline displacement model for the last 7 ka from eastern James Bay, Canada

The shoreline displacement history of the eastern James Bay lowlands in the last 7 ka has been investigated by means of AMS radiocarbon dating of sediments cored from wetlands. We present twelve radiocarbon dates on macrofossils from six sites spread along a gradient of increasing land age and elevation. Palynomorph analysis (pollen, spores, and dinoflagellate cysts) was used to define the isolation stratigraphy. During the last 7 ka the shoreline elevation has regressed at a decreasing rate. The rate of shoreline emergence was initially rapid (6. 5 m/ 100 yr) between 6850 and  6400 cal yr BP then slowed down to 1.4– 2 m/ 100 yr during the late Holocene. Examination of previous relative sea level data based upon mollusc shells reveals high levels of uncertainty that mask potential temporal variability.     

Sedimentation processes in an impoundment,Union lake,New Jersey

A small (3 75 km²) impoundment. Union Lake, on the Maurice River in southern New Jersey contains fine-grained sediment and organic material being transported through the surface water system Sedimentation is slow and rates calculated from¹³⁷Cs-dated cores indicate a decrease through time from 2 6 mm/yr to 0 57 mm/yr Sediment from shallow areas (<3 m) consists of winnowed preimpoundment fluvial sand, whereas sediment from deeper areas (>3 m) is dy composed of diatoms, organic matter, and silt- and clay-sized mineral grains Sediment distribution is controlled by water moving from the river entrance southward toward the outlet and by wind-generated water motion from shallow areas fringing the shore toward deeper portions of the impoundment     

The Legacy of Agricultural Reclamation on Channel and Pool Networks of Bay of Fundy Salt Marshes

We assess the status of channel networks and pools of two tidal salt marshes recovering from more than a century of agricultural reclamation on the Bay of Fundy, Canada. A process of largely unmanaged restoration occurred at these sites since abandonment of agricultural activities during the first half of the twentieth century. Each recovering marsh was compared to a reference marsh that was never drained or ditched. We field mapped channel networks at all marshes and used aerial photographs to map the pre-abandonment channel network at one of the sites. The recovering marshes have hybrid channel networks that feature highly variable channel morphologies, loss of original channels, and incorporation of drainage ditches. Although channel networks in recovering marshes integrate agricultural ditches, the recovering marsh networks may not be substantially increased in length or density. Our aerial photograph analysis shows that channel density at one of the recovering marshes is comparable to the pre-abandonment density, but with reduced sinuosity. Field mapping of permanent tidal pools on the lower Bay marshes revealed that pools cover 13% of the recovering marsh, compared to ∼5% of the reference marsh. This study demonstrates that these essential marsh features can be regained through restoration or simple abandonment of drainage infrastructure.     

Geological evolution of a pleistocene rhyolitic center — Sierra La Primavera, Jalisco, México

The Sierra La Primavera volcanic complex consists of late Pleistocene comenditic lava flows and domes. ash-flow tuff, air-fall pumice, and cold caldera-lake sediments. The earliest lavas were erupted about 120,000 years ago, and were followed approximately 95,000 years ago by the eruption of about 20 km³ of magma as ash flows that form the compositionally-zoned Tala Tuff. Collapse of the roof zone of the magma chamber led to the formation of a shallow 11-km-diameter caldera. It soon filled with water, forming a caldera lake in which sediment began to collect. At about the same time, two central domes erupted through the middle of the lake and a “giant pumice horizon”, an important stratigraphic marker, was deposited. Shortly thereafter ring domes erupted along two parallel arcs: one along the northeast portion of the ring fracture, and the other crossing the middle of the lake. All these events occurred during a period of approximately 5,000–10,000 years. Sedimentation continued and a period of volcanic quiescence was marked by the deposition of some 30 m of fine-grained ashy sediments virtually free from pumice lapilli. Approximately 75,000 years ago, a new group of ring domes erupted at the southern margin of the lake. These domes are lapped by only 10–20 m of sediments, as uplift resulting from renewed insurgence of magma brought an end to the lake. This uplift culminated in the eruption, beginning approximately 60,000 years ago, of aphyric lavas along a southern arc. The youngest of these lavas erupted approximately 20,000–30,000 years ago.The four major fault systems in the Sierra La Primavera are related to caldera collapse or to uplift caused by the insurgence of the southern are magma. Steam vents and larga-discharge 65°C hot springs are associated with the faulting. Calculated equilibrium temperatures of the geothermal fluids are 170°C, but temperatures in excess of 240°C have been encountered in an exploratory drill hole.A seismic survey showed attenuation of both S and P waves within the caldera, P waves attenuated more severely than S waves. The greatest attenuation is associated with an area of steam vents, and the rapid lateral variations in attenuation suggest that they are produced by a shallow geothermal system rather than by underlying magma.     

Thermal maturation, potential source rocks and hydrocarbon generation in Mesozoic rocks, Lougheed Island area, Central Canadian Arctic archipelago

Significant oil and gas accumulations occur in and around Lougheed Island, Arctic Canada, where hydrocarbon prospectivity is controlled by potential source rock distribution and composition. The Middle to Upper Triassic rocks of the Schei Point Group (e.g. Murray Harbour and Hoyle Bay formations) contain a mixture of Types I and II organic matter (Tasmanales marine algae, amorphous fluorescing bituminite). These source rocks are within the oil generation zone and have HI values up to 600 mg HC/g Corg. The younger source rocks of the Lower Jurassic Jameson Bay and the Upper Jurassic Ringnes formations contain mainly gas-prone Type II/III organic matter and are marginally mature. Vitrinite reflectance profiles suggest an effective geothermal gradient essentially similar to the present-day gradient (20 to 30°C/km). Maturation gradients are low, ranging from 0.125 to 0.185 log%Ro/km. Increases in subsidence rate in the Early Cretaceous suggest that the actual heat flow history was variable and has probably diminished from that time. The high deposition rates of the Christopher Formation shales coincide with the main phase of rifting in Aptian-Albian times. Uplift and increased sediment supply in the Maastrichtian resulted in a new sedimentary and tectonic regime, which culminated in the final phase of the Eurekan Orogeny. Burial history models indicate that hydrocarbon generation in the Schei Point Group took place during rifting in Early Cretaceous, long before any Eurekan deformation.     

Crystallisation sequence and magma evolution of the De Beers dyke (Kimberley,South Africa)

We present petrographic and mineral chemical data for a suite of samples derived from the De Beers dyke, a contemporaneous, composite intrusion bordering the De Beers pipe (Kimberley, South Africa). Petrographic features and mineral compositions indicate the following stages in the evolution of this dyke: (1) production of antecrystic material by kimberlite-related metasomatism in the mantle (i.e., high Cr-Ti phlogopite); (2) entrainment of wall-rock material during ascent through the lithospheric mantle, including antecrysts; (3) early magmatic crystallisation of olivine (internal zones and subsequently rims), Cr-rich spinel, rutile, and magnesian ilmenite, probably on ascent to the surface; and (4) crystallisation of groundmass phases (i.e., olivine rinds, Fe-Ti-rich spinels, perovskite, apatite, monticellite, calcite micro-phenocrysts, kinoshitalite-phlogopite, barite, and baddeleyite) and the mesostasis (calcite, dolomite, and serpentine) on emplacement in the upper crust. Groundmass and mesostasis crystallisation likely forms a continuous sequence with deuteric/hydrothermal modification. The petrographic features, mineralogy, and mineral compositions of different units within the De Beers dyke are indistinguishable from one another, indicating a common petrogenesis. The compositions of antecrysts (i.e., high Cr-Ti phlogopite) and magmatic phases (e.g., olivine rims, magnesian ilmenite, and spinel) overlap those from the root zone intrusions of the main Kimberley pipes (i.e., Wesselton, De Beers, Bultfontein). However, the composition of these magmatic phases is distinct from those in ‘evolved’ intrusions of the Kimberley cluster (e.g., Benfontein, Wesselton water tunnel sills). Although the effects of syn-emplacement flow processes are evident (e.g., alignment of phases parallel to contacts), there is no evidence that the De Beers dyke has undergone significant pre-emplacement crystal fractionation (e.g., olivine, spinel, ilmenite). This study demonstrates the requirement for detailed petrographic and mineral chemical studies to assess whether individual intrusions are in fact ‘evolved’; and that dykes are not necessarily produced by differentiated magmas.

     

Paleoenvironmental context of archaeological sites,implications for subsistence strategies under Holocene climate change,northern Kenya

The Holocene was time of dramatic climate change in East Africa, shifting from wetter climate in the Early–Mid Holocene (∼10–5ka) to drier climates in the Late Holocene, followed by a slight reversal at <1ka. The Holocene was a time of cultural change from hunter‐gatherer and fishing to pastoralism. Recent excavations along the eastern shores of Lake Turkana, Kenya (4°N) provide new archaeological materials, a high‐resolution stratigraphic and paleoenvironmental data set, OSL dates, and cultural records in the context of documented environmental change (falling lake levels). Archaeological site FwJj25 (4.20 ± 0.28ka), on the northeastern margin of Lake Turkana, provides one of the earliest records of pastoralism in the region. The palimpsest record of FwJj5 (0.90 ± 0.06ka) was in a small valley containing a groundwater seep located 5km from the lake. FwJj5 reflects occupation by people who may have covered great distances in accessing resources, but were likely drawn to an environmental refugia of freshwater springs during times of regional aridity. © 2011 Wiley Periodicals, Inc.