Saline wetlands related to groundwater flows from low permeability Tertiary formations in the Somontano area of Huesca,Spain

Presence of groundwater flow in the ‘Somontano de Huesca’ Area, derived from low‐permeability detrital Tertiary rocks, is considered. A groundwater flow model is constructed for these Tertiary rocks. This model explains both water flow through them and the chemical characteristics of the water. Groundwater flow has clear surface manifestations: it causes wetlands (which are called ‘paules’ in the area) with sodic waters, it produces saline, sodic or alkaline soils, and it produces modifies the chemical composition of rivers in Somontano. Irrigation has increased the volume of filtered water, especially in the interfluve areas, causing the extension of the wetlands in the valley thalwegs, and also the greater movement of salts has increased the problems of saline and/or sodic soils in the area. Copyright © 2001 John Wiley & Sons, Ltd.     

Petrology of Fe-Mg-carpholite-bearing metasediments from NE Oman

Abstract Fe-Mg carpholite occurs in metasediments of tectonically disrupted basement, shelf and foreland basin units that structurally underlie the Semail ophiolite in NE Oman. In the lower grade, structurally higher units, Fe-rich carpholite coexists with paragonite, quartz, illite, kaolinite and chlorite, whereas in deeper units, Fe-Mg carpholite occurs with pyrophyllite, sudoite, phengite and/or chloritoid. Mineral compositions in these units indicate that chlorite is more magnesian than coexisting Fe-Mg carpholite at low temperatures and pressures but, at higher metamorphic grades, X_Mg decreases in the order sudoite > carpholite > chlorite > chloritoid. This suggests a reversal in Fe-Mg partitioning between Fe-Mg carpholite and chlorite at temperatures below or close to those of the breakdown of kaolinite + quartz to pyrophyllite and at X_Mg= 0.35.
Phase relations and mineral equilibria indicate that the P-T conditions of formation of the Fe-Mg-carpholite-bearing rocks of NE Oman range from 280–315° C, 3–6 kbar for the structurally highest units to 325–440° C, 6–9.5 kbar for the deepest units, indicating a systematic down-section increase in metamorphic grade. Textural relations in these rocks, interpreted in the context of pertinent equilibria, are consistent with the clockwise P-T paths previously constrained for these units from petrological studies of interlayered isofacial mafic rocks.     

Integrated biostratigraphy and chemostratigraphy of the upper Cenomanian and lower Turonian succession in Puentedey, Iberian Trough, Spain

In this paper, we present an integrated study of the macrofauna (Cephalopoda), microfauna (Ostracoda and Foraminifera), microflora (Pithonella, Dinoflagellata, Acritarcha and Prasinophyta) and geochemical signals (carbon δ¹³C and oxygen δ¹⁸O stable isotopes) of the upper Cenomanian and lower Turonian succession in Puentedey, Iberian Trough, Spain. This palaeontological and geochemical study has enabled us to identify numerous species of cephalopods (29), ostracods (19), benthic foraminifers (31), planktonic foraminifers (15), dinoflagellates (63), and acritarchs and prasinophytes (11), and to recognise two positive excursions of the δ¹³C signal related to the OAE2 (in the Metoicoceras geslinianum and the Spathites (Jeanrogericeras) subconciliatus zones, respectively). Variations of these macrofaunal, microfaunal, microfloral and geochemical signals have been interpreted to identify important events of the palaeoenvironmental evolution of the inner platform of the Iberian Trough during the studied interval of the Late Cretaceous. Benthic ecosystems were severely affected by the establishment of the Oceanic Anoxic Event 2 (OAE2) at the end of the late Cenomanian. This event is evidenced by the depletion of calcareous microfauna (benthic calcareous free intervals, BCFI) and the survival of opportunistic microfauna (platycopic ostracods and textulariid foraminifers). The response was different for microflora (dinoflagellates and acritarchs), which were less affected by the anoxic event.     

Coastal storm characterization and morphological impacts on sandy coasts

The present work deals with storm classification, using the Storm Power Index, and beach morphological response to storm events in the Gulf of Cadiz (SW Spain). Over the 1958–2001 period, 377 events divided into five classes ranging from ‘weak’ to ‘extreme’ were characterized. Classes I (weak) and II (moderate) accounted for 60% and 23% of events, respectively. Class III (significant), were 9% of the recorded events and Classes IV (severe) and V (extreme) accounted for 5% and 2%, respectively. The probability of storm occurrence per year ranged from 93% for Class I to 15% for Class V. In order to characterize beach response to storm events, 214 beach profiles carried out with a monthly periodicity over the 1996–1998 period along the Chipiona‐Rota littoral were analysed, as well as published data. Different beach types were observed: (i) ‘Intermediate’ beaches underwent important vertical relief changes ranging from 0.3 m to 1.33 m associated with average slope changes from tan β = 0.06 to tan β = 0.03; (ii) the ‘dissipative’ beaches were characterized by smaller and homogeneous foreshore vertical changes, from c. 0.36 m to 0.65 m, according to the parallel retreat mechanism characterized by small slope variations (from tan β = 0.025 to tan β = 0.035); and (iii) ‘intermediate with rock shore platform’ experienced small morphological and foreshore slope variations, related to both beach pivoting and parallel retreat mechanisms. The most important morphological changes were due to the impact of usually ‘weak’ and ‘moderate’ events during October and November that produced berm erosion and upper foreshore lowering, and the impact of ‘severe’, ‘significant’ and ‘extreme’ events in December and January which produced dune escarpment, overwash and/or damage to coastal structures. Copyright © 2011 John Wiley & Sons, Ltd.     

Larger foraminifera distribution and strontium isotope stratigraphy of the La Cova limestones (Coniacian–Santonian, “Serra del Montsec”, Pyrenees, NE Spain)

The Upper Cretaceous La Cova limestones (southern Pyrenees, Spain) host a rich and diverse larger foraminiferal fauna, which represents the first diversification of K-strategists after the mass extinction at the Cenomanian–Turonian boundary.The stratigraphic distribution of the main taxa of larger foraminifera defines two assemblages. The first assemblage is characterised by the first appearance of lacazinids (Pseudolacazina loeblichi) and meandropsinids (Eofallotia simplex), by the large agglutinated Montsechiana montsechiensis, and by several species of complex rotalids (Rotorbinella campaniola, Iberorotalia reicheli, Orbitokhatina wondersmitti and Calcarinella schaubi). The second assemblage is defined by the appearance of Lacazina pyrenaica, Palandrosina taxyae and Martiguesia cyclamminiformis.A late Coniacian-early Santonian age was so far accepted for the La Cova limestones, based on indirect correlation with deep-water facies bearing planktic foraminifers of the Dicarinella concavata zone. Strontium isotope stratigraphy, based on many samples of pristine biotic calcite of rudists and ostreids, indicates that the La Cova limestones span from the early Coniacian to the early-middle Santonian boundary. The first assemblage of larger foraminifera appears very close to the early-middle Coniacian boundary and reaches its full diversity by the middle Coniacian. The originations defining the second assemblage are dated as earliest Santonian: they represent important bioevents to define the Coniacian-Santonian boundary in the shallow-water facies of the South Pyrenean province.By means of the calibration of strontium isotope stratigraphy to the Geological Time Scale, the larger foraminiferal assemblages of the La Cova limestones can be correlated to the standard biozonal scheme of ammonites, planktonic foraminifers and calcareous nannoplankton. This correlation is a first step toward a larger foraminifera standard biozonation for Upper Cretaceous carbonate platform facies.     

海拉尔盆地贝尔凹陷构造演化

基于地震剖面,运用平衡剖面复原技术,将贝尔凹陷划分4个形成期：断陷期（铜钵庙组、南屯组）、断坳期（大磨拐河组、伊敏组）、坳陷期（青元岗组）和萎缩期（新生代）;4个改造期：南屯组一段及南屯组二段沉积末期张扭变形期、伊敏组沉积末期张扭变形期和青元岗组沉积末期反转变形期.     

Nitrate as a tracer of groundwater flow in a fractured multilayered aquifer

Abstract

Knowledge of the processes that control nitrate migration and its geochemical evolution in the subsurface are fundamental for the regional management of polluted aquifers. In this paper, the spatial distribution and transient variations of nitrate concentrations, associated with manure fertilization, are used to depict hydrogeological dynamics within the sedimentary aquifer system of la Plana de Vic in the Osona region of Spain. Flow systems are identified from geological, hydraulic head, hydrochemical and isotopic data, and by considering nitrate itself as a tracer that indicates how flow paths are modified by human pressures. In this area, nitrates move through fractured aquitards in flows induced by groundwater pumping. Moreover, the lack of casing in the boreholes permits a mixing of groundwater from distinct layers inside the wells, which negates any benefits from the low-nitrate groundwater found in the deepest aquifer layers. Therefore, impacts on groundwater quality are related to intensive manure fertilization as well as to inadequate well construction and exploitation strategies.

Citation Menció, A., Mas-Pla, J., Otero, N. & Soler, A. (2011) Nitrate as a tracer of groundwater flow in a fractured multilayered aquifer. Hydrol. Sci. J. 56(1), 108–122.     

Comparative performance of soil water balance models in computing semi-arid aquifer recharge

Abstract

Estimating groundwater recharge is essential to ensure the sustainable use of groundwater resources, particularly in arid and semi-arid regions. Soil water balances have been frequently advocated as valuable tools to estimate groundwater recharge. This article compares the performance of three soil water balance models (Hydrobal, Visual Balan v2.0 and Thornthwaite) in the Ventós-Castellar aquifer, Spain. The models were used to simulate wet and dry years. Recharge estimates were transformed into water table fluctuations by means of a lumped groundwater model. These, in turn, were calibrated against piezometric data. Overall, the Hydrobal model shows the best fit between observed and calculated levels (r² = 0.84), highlighting the role of soil moisture and vegetation in recharge processes.

Editor D. Koutsoyiannis; Associate editor X. Chen

Citation Touhami, I., et al., 2014. Comparative performance of soil water balance models in computing semi-arid aquifer recharge. Hydrological Sciences Journal, 59 (1), 193–203.     

Quaternary exhumation history of the NE Tibetan Plateau revealed by peculiar distributions of polycyclic aromatic hydrocarbons in core extracts from the Sanhu depression,eastern Qaidam basin

Reworked organic matter (ROM) has been frequently encountered in fresh organic matter (FOM) in young sedimentary basins. Our study reports an ROM-dominated sequence from 21 borehole cores of the Late Pliocene–Quaternary strata in the Sanhu depression of the eastern Qaidam basin in northwestern China. Reworked organic matter occurrence is confirmed by Rock-Eval pyrolysis results, high Ro values, and reversed polyaromatic hydrocarbon (PAH) maturity trends showing elevated maturities. Rock–source correlation using molecular fingerprints of biomarkers shows ROM was derived from Jurassic freshwater lacustrine source rocks dominated by terrestrial input, contrasting the immature Quaternary FOM developed in anoxic, saline lacustrine facies. The ROM provenance is traced northward to the southern Qilian Mountains. Maximum burial depths of ROM prior to erosion have been inferred by a burial depth–Rc (calculated vitrinite reflectance) correlation. Two chronological boundaries (1.83 Ma and 3.12 Ma) displaying distinct biomarker fingerprints are obtained from a previously reported chronological framework in the study area. Accordingly, an eroded thickness of 1214 m and an average erosion rate of 94 cm/ka of the ROM provenance areas during this temporal interval are derived. Our study has illustrated the potential value of geochemical compositions of ROM with constrained provenances in investigating the exhumation history of a mountain.