Biometry of late Quaternary coccoliths from the Southern Cadiz region

The Cadiz region lies between the Iberian borderland and Morocco, west of the Strait of Gibraltar and the Western Mediterranean. Core GeoB9064-1 (35°24,91’N 6°50,72’W) is located in the southwest at a depth of 702 m, close to the Al Arraich mud volcano field 30 km off the Moroccan margin„ and has a length of 544 cm. Like most coastal regions, the southern Cadiz region is characterised by a coccolith assemblage dominated by the placoliths Emiliania huxleyi and Gephyrocapsa muellerae.Late Quaternary fluctuations are pronounced in this core, as shown by geochemical (TOC and CaC03) and XRF analysis (K, Mg, Fe, etc.), but also in abundances of coccoliths and more particularly Emiliania huxleyi. These can be related to upwelling and/or bottom currents.Colmenero-Hidalgo (2002) has split up Emiliania huxleyi in a larger coldwater and smaller warmwater variety based on a 4 µm cut-off value. Colmenero-Hid algo (2004) identified a deglacial decrease in the larger coldwater variety.In this study, 100 Emiliania huxleyi and 100 Gephyrocapsa muellerae lengths were measured in 30 samples. Comparison of the biometry of Emiliania huxleyi and Gephyrocapsa muellerae shows that these both species have similar fluctuations and both become smaller during the Holocene, revealing the splitting of Emiliania huxleyi in two morphotypes, to be more complex. A new method to tackle this problem is proposed

A 3000 year chronology of North Anatolian Fault ruptures, utilizing magnetic susceptibility trench logging, near Lake Ladik, Turkey

Understanding the irregularity of seismic cycles: A case study in Turke

Traces of the last earthquake sequence (1939-1944) along NAF from lacustrine sediments

Understanding the irregularity of seismic cycles: A case study in Turke

Scalar decay in a three-dimensional chaotic flow

The decay of a passive scalar in a three-dimensional chaotic flow is studied using high-resolution numerical simulations. The (volume-preserving) flow considered is a three-dimensional extension of the randomised alternating sine flow employed extensively in studies of mixing in two dimensions. It is used to show that theoretical predictions for two-dimensional flows with small diffusivity carry over to three dimensions even though the stretching properties differ significantly. The variance decay rate, scalar field structure, and time evolution of statistical moments confirm that there are two distinct regimes of scalar decay: a locally controlled regime, which applies when the domain size is comparable to the characteristic lengthscale of the velocity field, and a globally controlled regime, which when applies when the domain is larger. Asymptotic predictions for the variance decay rate in both regimes show excellent agreement with the numerical results. Consideration of both the forward flow and its time reverse makes it possible to compare the scalar evolution in flows with one or two expanding directions; simulations confirm the theoretical prediction that the decay rate of the scalar is the same in both flows, despite the very different scalar field structures

A surface-aware projection basis for quasigeostrophic flow

Recent studies indicate that altimetric observations of the ocean's mesoscale eddy field reflect the combined influence of surface buoyancy and interior potential vorticity anomalies. The former have a surface-trapped structure, while the latter have a more grave form. To assess the relative importance of each contribution to the signal, it is useful to project the observed field onto a set of modes that separates their influence in a natural way. However, the surface-trapped dynamics are not well-represented by standard baroclinic modes; moreover, they are dependent on horizontal scale. Here we derive a modal decomposition that results from the simultaneous diagonalization of the energy and a generalisation of potential enstrophy that includes contributions from the surface buoyancy fields. This approach yields a family of orthonomal bases that depend on two parameters: the standard baroclinic modes are recovered in a limiting case, while other choices provide modes that represent surface and interior dynamics in an efficient way. For constant stratification, these modes consist of symmetric and antisymmetric exponential modes that capture the surface dynamics, and a series of oscillating modes that represent the interior dynamics. Motivated by the ocean, where shears are concentrated near the upper surface, we also consider the special case of a quiescent lower surface. In this case, the interior modes are independent of wavenumber, and there is a single exponential surface mode that replaces the barotropic mode. We demonstrate the use and effectiveness of these modes by projecting the energy in a set of simulations of baroclinic turbulence

Small-molecule screens to study lateral root development

Development of the root system is essential for proper plant growth and development. Extension of the root system is achieved by the continuous establishment of new meristems in existing parental root tissues, which leads to the development of lateral roots. This process of lateral root organogenesis consists of different developmental stages, which are all controlled by the plant hormone auxin. In this chapter, we describe a screening method in Arabidopsis thaliana to identify small synthetic molecules that interfere with the process of lateral root development during specific developmental stages

Development of paleoseismic trench logging and dating techniques: a case study on the Central North Anatolian Fault

The North Anatolian Fault (NAF) is a dextral strike slip fault zone extending ~1400km in an arc across northern Turkey. This study seeks to further constrain the timing of ground rupturing earthquakes of the NAF while developing the techniques used in paleoseismology. A paleoseismic trench was opened ~2.7km NW of Destek on a segment which ruptured (for ~280km) in the 1943 Tosya Earthquake (Mw:7.7). The trench site comprises a pop-up structure formed by a small releasing step-over at a restraining bend which has caused progressive growth of an upslope facing scarp. The trench is situated across the main fault trace and a trapped sedimentary sequence that includes several paleosoils. The stratigraphy is expected to be Late Holocene and historic in age due to the high level of activity on the NAF, although this has yet to be confirmed by radiometric dating. Preliminary interpretation of the trench stratigraphy indicates a record of up to 6 paleoearthquake events, the presence of an angular unconformity suggests the record may be incomplete beyond the 3 most recent events on this strand.Subtle contrasts in stratigraphy made conventional face logging difficult and was therefore augmented by mapping the magnetic susceptibility (MS) of the west wall. Approximately 6000 measurements were made using a Bartington MS2 Magnetic Susceptibility Meter with a MS2E (point) Sensor with a 5cm vertical spacing and a 20cm horizontal spacing predominantly on one side of the trench. A pilot test led to development of a strategy of moving the sensor to the nearest exposure of coarse sand or finer grained material where possible to minimize the noise generated by individual clasts. To negate the sensitivity of the MS logging method to variations in temperature the survey was conducted at night. Plotted data clearly shows the contact between rock units, the rock-soil interface (reflecting fault juxtaposition), anthropogenic influence and some soil stratigraphy. Other paleoseismic investigations on this section of the NAF (Hartleb R. et al 2003 and Yoshioka T. et al 2000) have encountered out-of-stratigraphic-order ranges in 14C ages. They attributed this to reworking, in addition to which the effects of long term human occupation are likely to be similar. The trench yielded a large amount of datable material including 158 charcoal and 140 minute gastropod samples, and some ceramic, bone and slag samples. Unlike charcoal and bone fragments, fragile minute gastropods are unlikely to have been transported, reworked or used by humans, ultimately providing improved accuracy of temporal constraints on paleoearthquakes. Using both charcoal and gastropod samples, the trench chronology can be established and the use of minute gastropods for dating paleoearthquakes can be critiqued