The impact of salt on the late Messinian to recent tectonostratigraphic evolution of the Cyprus subduction zone

Messinian evaporites of locally more than 3‐km thickness occupy the subduction zone between Cyprus and Eratosthenes Seamount. Based on a dense grid of seismic reflection profiles, we report on compressional salt tectonics and its impact on the Late Miocene to Quaternary structural evolution of the Cyprus subduction zone. Results show that evaporites have experienced significant post‐Messinian shortening along the plate boundary. Shortening has initiated allochthonous salt advance between Cyprus and Eratosthenes Seamount, representing an excellent example of salt which efficiently escapes subduction and accretion. Further east, between Eratosthenes Seamount and the Hecataeus Rise, evaporites were compressionally inflated without having advanced across post‐Messinian strata. Such differences in the magnitude of salt tectonic shortening may reflect a predominately north–south oriented post‐Messinian convergence direction, raising the possibility of a later coupling between the motion of Cyprus and Anatolia than previously thought. Along the area bordered by Cyprus and Eratosthenes Seamount a prominent step in the seafloor represents the northern boundary of a controversially debated semi‐circular depression. Coinciding with the southern edge of the salt sheet, this bathymetric feature is suggested to have formed as a consequence of compressional salt inflation and seamount‐directed salt advance. Topographic lows on top of highly deformed evaporites are locally filled by up to 700 m of late Messinian sediments. The uppermost 200 m of these sediments were drilled in the course of ODP Leg 160 and interpreted to represent Lago Mare‐type deposits (Robertson, Tectonophysics, 1998d, 298 , 63‐82). Lago Mare deposits are spatially restricted to the western part of the subduction zone, pinching out towards the east whereas presumably continuing into the Herodotus Basin further west. We suggest a sea level control on late Messinian Lago Mare sedimentation, facilitating sediment delivery into basinal areas whereas inhibiting Lago Mare deposition into the desiccated Levant Basin. Locally, early salt deformation is believed to have provided additional accommodation space for Lago Mare sedimentation, resulting in the presently observed minibasin‐like geometry.     

Aromatic ketones concentrated from Baltic Sea water

Aromatic ketones were concentrated from filtered Baltic Sea water by liquid—solid adsorption. After wet-chemical separation from acidic and basic components, the neutral fraction was column chromatographed to yield sub-fractions of increasing polarity. A subfraction eluted from silica gel with cyclopentane/diethyl ether contained a number of compounds which were identified by GC and GC—MS techniques as fluorenone, anthraquinone, benzanthrone, and benzene derivatives carrying an oxo group in the α-position relative to the aromatic ring. Formation and abiotic chemical reactions of these compounds in seawater are discussed.     

Natural seepage of petroleum at Buchan Gulf,Baffin Island

Analyses by fluorescence spectrophotometry and computerized gas chromatography/mass spectrometry of the hydrocarbons present in surficial bottom sediments from Buchan Gulf, Baffin Island established that natural seepage of petroleum is occurring from the seabed. In addition, compounds of recent biosynthetic origin and from atmospheric fall-out of combustion products were identified.     

Conrad Deep, Northern Red Sea: Development of an early stage ocean deep within the axial depression

The northern Red Sea represents a continental rift in its final stage and close to the following stage of seafloor spreading. Ocean deeps within the evaporites of the northern Red Sea seem to accompany this process and are thought to be surface expressions of first seafloor spreading cells. In 1999 during R/V Meteor cruise M44/3 a dense multichannel seismic and hydroacoustic survey was conducted in order to investigate the initial formation process of the Conrad Deep, a young northern Red Sea deep. Three seismic units were differentiated in the uppermost part of the Miocene evaporites and the Plio-Quaternary sediments. A weakness zone within the evaporites, oblique to the main extension direction of the Red Sea, led to a transtension process within the evaporites that opened the deep. Its formation is directly related to the emplacement of magmatic bodies in its vicinity and the focusing of the Red Sea extension to the axial depression. The Conrad Deep is an intra-evaporite basin that cannot be regarded as surficial expression of a basement structure as the low shear strength of the evaporites decouple the sediments from the basement. However, its position and shape in combination with the accompanying geophysical anomalies point to a strong correlation with the Red Sea rifting process.     

Pink shrimp,Farfantepenaeus duorarum,recruitment variability as an indicator of Florida Bay dynamics

Florida Bay exhibits highly dynamic hydrographic regimes that influence variability in the retention, survivorship, and migration of pink shrimp,Farfantepenaeus duorarum, larvae and juveniles. Florida Bay is the nursery habitat for pink shrimp and since a large fishery is based on the adult population in the Dry Tortugas region, Florida Bay plays a fundamental role in the health of the pink shrimp fishery in South Florida. Conversely, the level of shrimp recruitment to the fishery can act as an indicator of the health of Florida Bay integrating multiple biological, physical, and environmental variables. We examined 372 mo of data on commercial landings of pink shrimp to estimate monthly recruitment. We found recruitment occurs throughout the year, there are one or more seasonal peaks, and the magnitude and monthly position of the peaks changed through decades. These changes may be explained by a varying spawning population producing different levels of eggs, by environmental changes in the nursery grounds that modulate a nearly constant supply of eggs, or a combination of these. Recruitment estimates and the residuals about stock-recruitment relationships were compared over three decades (1965–1995) in terms of annual and monthly trends and average patterns. Significant differences found between the decades could be due to ecological changes in Florida Bay, specifically to loss of recruitment peaks, with an associated overall decline in pink shrimp recruitment. For the lates years of the study, recruitment and residuals about the stock-recruitment curve are increasing, which may indicate an improvement in Florida Bay as a nursery ground for pink shrimp, and thus as habitat for other organisms as well.     

Phthalate esters in the Kiel Bight

Phthalate plasticizers have been accumulated from filtered seawater by liquid—solid adsorption, and in suspended organic matter collected on glass-fibre filters. They were characterized by gas chromatographic retention indices and by their mass spectra. Single-ion detection, focused on m/e 149, was used as a selective and sensitive method to quantify different phthalate esters in Baltic seawater in the 1:10¹⁰–1:10¹¹ concentration range.     

Decomposition reactions of magnesium sulfate hydrates and phase equilibria in the MgSO4-H2O and Na-Mg-Cl-SO4-H2O systems with implications for Mars

We report new measurements of equilibrium relative humidities for stable and metastable hydration-dehydration equilibria involving several magnesium sulfates in the MgSO₄·nH₂O series. We also report a comprehensive thermodynamic treatment of the system including solution properties and experimental data from the published literature, i.e. solubilities, heat capacities and additional decomposition humidities. While for some magnesium sulfate hydrates solubility data in the binary system MgSO₄-H₂O are sparse, there is a reasonable database of solubility measurements of these hydrates in the ternary MgCl₂-MgSO₄-H₂O and the quaternary reciprocal Na⁺-Mg²⁺-Cl⁻-SO₄²⁻-H₂O systems. To make these data suitable for the determination of solubility products, we parameterized a Pitzer ion interaction model for the calculation of activity coefficients and water activities in mixed solutions of these systems and report the ion interaction parameters for the Na⁺-Mg²⁺-Cl⁻-SO₄²⁻-H₂O system. The model predicted solubilities in the reciprocal system are in very good agreement with experimental data. Using all available experimental data and the solution model an updated phase diagram of the MgSO₄-H₂O system covering the whole temperature range from about 170 to 473 K is established. This treatment includes MgSO₄·H₂O (kieserite), MgSO₄·4H₂O (starkeyite), MgSO₄·5H₂O (pentahydrite), MgSO₄·6H₂O (hexahydrite), MgSO₄·7H₂O (epsomite) and MgSO₄·11H₂O (meridianiite). It is shown that only kieserite, hexahydrite, epsomite and meridianiite show fields of stable existence while starkeyite and pentahydrite are always metastable. Due to sluggish kinetics of kieserite formation, however, there is a rather extended field of metastable existence of starkeyite which makes this solid a major product in dehydration reactions. The model predicted behavior of the magnesium sulfates is in excellent agreement with observations reported in the literature under terrestrial temperature and relative humidity conditions. We also discuss the implications of the new phase diagram for sulfates on Mars.