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The south- to southwest-dipping North and South Saros normal faults occupy the southeastern margin of the Gerania Range, a major massif of Mesozoic limestone and ophiolite in the eastern Gulf of Corinth Rift, central Greece. The history of the Saros faults is constrained by adjacent basin-fill sediments and modern drainage patterns. Older basin fill (Pliocene--lower Pleistocene?), which consists of terrestrial fine sands, carbonaceous muds, marls, and micrite limestones, is uplifted on the South Saros fault block and onlaps the North Saros fault footwall block on its northern side to near its crest, suggesting that it predates major fault activity. In contrast, younger basin fill (middle Pleistocene?) was deposited and locally deformed during fault activity in a main basin south of the faults and in a perched basin on the South Saros fault block. Main-basin deposits consist of alluvial-fan, fan-delta, and shallow-marine sediments up to 50 m thick, whereas perched-basin fanglomerates are 5-15 m thick. Fault-scarp retreat and sediment onlap indicate that the faults became inactive late in the history of deposition of the younger basin fill. The perched and main basins are currently undergoing incision, allowing modern sediment to bypass the basins and to be deposited on modern fan deltas and beaches along the Gulf of Megara coast. The absence of knickpoints and upstream deepening of the canyons suggest that a climatically driven increase in catchment runoff was responsible for basin incision, although uplift and sea-level change may have contributed as well. The North and South Saros faults each consist of three segments characterized by different strikes. The major drainages cross the Saros faults at or near segment boundaries, suggesting that the drainages may have initially flowed between the tips of isolated fault segments. As the segments became linked, the antecedent drainages maintained their course and cut deep gorges. At the scale of the entire eastern Gulf of Corinth region, however, older unlinked faults were abandoned, and new faults were created in a general northward and basinward direction; the origin of this process remains controversial.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2006.07.002 Byline: Greg H. Mack (a), William R. Seager (a), Mike R. Leeder (b), Marta Perez-Arlucea (c), Stephen L. Salyards (d) Keywords: Rio Grande rift; fluvial; Pliocene and Quaternary; New Mexico Abstract: The history of the Rio Grande, the axial river of the southern Rio Grande rift, New Mexico, may be divided into an aggradational phase ([approximately equal to] 5 to [approximately equal to] 0.8 Ma), during which time about 100 m of fluvial sediment was deposited in eight basins, and a degradational phase ([approximately equal to] 0.8 Ma to present), when the river alternately incised and partially backfilled its basins. Reversal magnetostratigraphy, dated volcanic rocks, and vertebrate biostratigraphy allow correlation of sediment of the aggradational phase with the Gilbert, Gauss, and Matuyama Chrons, while the degradational phase primarily encompasses the Brunhes Chron. Tectonics was the primary control on river behaviour during the aggradational phase. In half grabens, multistorey channel sands were deposited in narrow belts near the footwall uplifts, in response to tilt of the basin floor towards the border fault and smaller footwall catchments and their alluvial fans compared to those of the hanging-wall mountains. In contrast, the river traversed almost the entire width of full grabens, depositing interbedded channel and floodplain sediment with moderately mature palaeosols. Condensed sections dominated by floodplain sediment with very mature palaeosols developed in basins largely abandoned by the river due to preferential tilting of the basin floor, lateral growth or renewal of fault activity, or alternating flow of the river between adjacent basins. The degradational phase was dominated by net basin erosion related to glacial-climate cycles, despite continued activity on many of the basin-bounding faults. Author Affiliation: (a) Department of Geological Sciences, New Mexico State University, Las Cruces, NM 88003, USA (b) School of Environmental Sciences, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK (c) Departemento de Geosiencias Marinas, F. Ciencias, Universidad de Vigo, 36200, Vigo, Spain (d) Department of Earth and Space Sciences, UCLA, Los Angeles, CA 90024, USA Article History: Received 29 November 2005; Accepted 4 July 2006

The kinematic and erosional history of the Rio Grande uplift, a large northwest-trending, basement-involved, thrust-bounded, block uplift of Laramide age (latest Cretaceons-early Tertiary) in south-central New Mexico, is documented by elastic rocks that accumulated in the complementary Love Ranch basin. The synorogenic to postorogenic McRae and Love Ranch Formations are as much as 1460 m thick: they filled the Love Ranch basin and onlapped the Rio Grande uplift. Present outcrops of the two formations cover an area of 100 [km.sup.2] and reveal the stratigraphic architecture of the basin fill in three dimensions. Lithofacies distribution, clast size and composition, paleoflow data, syndepositional structures, nature of the basal unconformities, and ages of basin fill provide essential data for constraining uplift history. Laramide shortening began between Campanian and latest Maastrichtian time, and initially created open, symmetrical, northwest-trending folds, as well as a broad, approximately symmetrical uplift. This incipient Rio Grande uplift was capped by Upper Cretaceous volcanic rocks of intermediate and silicic composition, which were the primary source of volcanic detritus in the latest Cretaceous-Paleocene(?) McRae Formation. At this stage of uplift, the northeastern flank dipped gently northeastward away from the crest and served largely as a sediment transport surface; McRae strata accumulated only on distal parts of the surface in an embryonic Lure Ranch basin to the northeast. Following an interruption in tectonism lasting as much as 10 m.y., renewed shortening in Paleocene(?) time elevated the Rio Grande uplift and formed the Love Ranch basin. At least 900 m of upward-fining, elastic Love Ranch strata of Paleocene-Eocene age accumulated in the basin. The Love Ranch lithofacies record a gradual southwestward shift of alluvial-fan depocenters, which resulted from growth of basin-margin structures and increasing basin asymmetry. Syndepositional synclines and angular unconformities record the growth of both intrabasinal folds and basin-margin thrusts. Clast compositions document progressive erosional unroofing of the Rio Grande uplift from Upper Cretaceous volcanic rocks into Precamhrian granite anti metamorphic rocks. Canyons 0.4 km deep locally drained the uplift, and maximum topographic relief may have approached 2 km. By late Eocene time, Love Ranch piedmont-slope deposits onlapped the uplift, burying all hut the higher granite peaks. At this stage, the Love Ranch basin broadened and was the site of broad alluvial plains crossed by braided rivers draining to saline lakes. Our analysis of syntectonic sedimentary rocks in the Love Ranch basin supports recent models of evolution of Laramide basement-involved block uplifts in which early stages produce approximately symmetrical structures, and sediment derived from the uplift is transported across must of the uplift flank to he deposited in a distal selling. At this stage the future footwall of uplift-boundary faults dips basin-ward in a ramp-like fashion, providing a sediment transport surface. As boundary thrust faults and fault-propagation folds evolve and grow basin asymmetry rapidly develops, causing depocenters to shift toward footwall positions near the overthrust margins. This evolution from symmetrical to asymmetrical structures is reflected in an overall upward-fining sequence in the basin fill.

Since 1978 the results of computational architectural models have been widely used to aid interpretation of ancient alluvial successions: here we present the first quantitative test of such models. We parameterize variables from field and magnetostratigraphic data collected from the well-exposed Pliocene-Pleistocene Camp Rice and Palomas Formations of the Rio Grande rift in south-central New Mexico. Computational runs establish that the LAB (Leeder, Allen, and Bridge) model correctly predicts the gross architectural patterns of ancestral axial Rio Grande half grabens and full grabens. Convergence of tectonic subsidence rate and mean sedimentation rate over the studied interval suggests that the dynamic basis of the models is correct; i.e., it is the tectonic 'draw-down' of axially supplied sediment that controls the net preservation potential of alluvial successions.

The pedologic, sedimentologic and stratisgraphic conclusions of a study on the Mississippian Monteagle Limestone in Tennessee and Alabama is inconsistent with previous data on the Hartselle Sandstone. Interpretations of the tectonic origins of the orogenic belts in the Appalachian and Ouachita regions were based on arguments concerning the southward progradation of the Hartselle Sandstone.

Three different paleoclimate stages are exhibited by the study of stable carbon and oxygen isotopes of pedogenic carbonate of Camp Rice Formation. The first stage has a low-level of C-13 and O-18 isotopes. During this stage, the isotopic values increase with a reduction in age. During the second stage, there is an increase in the oxygen isotope concentration with reduction in age. There is an overall increase in both oxygen and carbon content in the last stage.

Despite increased interest in paleosols during the past decade, no satisfactory classification is in current use. Presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record. Emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope. The classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes: organic matter content, horizonation, redox conditions, in situ mineral alteration, illuviation of insoluble minerals/compounds, and accumulation of soluble minerals. The most prominent of these six features/processes provides the key to classifying a paleosol into one of nine orders. Four of the order names are borrowed from Soil Taxonomy (Histosol, Spodosol, Oxisol, Vertisol), whereas the other five order names are presented here for the first time (Calcisol, Gypsisol, Gleysol, Argillisol, Protosol). The orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol. The classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology.

Estimates of climate derived from the foliar physiognomy of modern vegetation indicate that, for modern test sites, the calculated climates can differ from actual climates and are sensitive to the equation used to quantify the leaf/climate relationship (or transfer function). To determine how estimates of past climates can vary in response to transfer function, we analyzed a latest Cretaceous (Maastrichtian) leaf assemblage from the Jose Creek Member of the McRae Formation, southern New Mexico, in part because of its relevance to climatic change across the Cretaceous-Tertiary boundary. The Jose Creek assemblage represents probable in situ leaf litter preserved in volcanic ash and was derived from vegetation growing in well-drained soil. The analyzed assemblage consists of 132 specimens of dicot leaves belonging to 43 species, which are associated with a comparable number of ferns, conifers, and thermophilic monocots belonging to at least 10 species. Estimates of mean annual temperature (MAT) and mean annual precipitation (MAP) were made using published univariate and multivariate transfer functions derived from the CLAMP database of Wolfe or regional floras. Calculations were made using raw physiognomic data and data adjusted to account for the over-representation of small leaves in modern leaf litter. Calculated MAT for the Jose Creek assemblage generally ranges from 16-21 [degrees] C, with multivariate transfer functions tending to give cooler values than univariate transfer functions. Calculated MAP ranges from under 800 to over 1500 mm per year, with an average of 1100 mm. Variation in calculated temperature and precipitation, relative to the mean of all estimates, can exceed [+ or -] 235%, underscoring the potential bias introduced by choice of transfer function. However, the range of values is congruent with more qualitative estimates of climate derived from fossil soils and plant life form, which indicate warm moist conditions and above-freezing cold-month means for the Jose Creek Member.

Nine types of authigenic carbonate are present in the Pliocene-Pleistocene alluvialfan and axial-fluvial sediment of the Palomas half graben in the southern Rio Grande rift. Pedogenic and other vadose carbonate includes (1) pedogenic carbonate of stage II and stage III morphology underlying Bw and Bt horizons, (2) mudstones in which the carbonate nodules may be pedogenic or the result of shallow groundwater invasion of the vadose zone, (3) pedogenic calcic nodules and tubules in eolian sand, and (4) gully-bed cement of proximal-fan conglomerates formed by infiltration and evaporation of surface runoff. Shallow groundwater carbonate exists as (5) thin (30-50 cm), massive beds with an upper fringe of nodules and tubules precipitated at the water table and in the capillary fringe, (6) thick (1.5-3 m), massive beds deposited by lateral flow of groundwater or at springs, and (7) thin (30 cm), calcified root mats associated with near-surface, water-saturated sediment or springs. Phreatic spar cements (8) occupy the interstices of conglomerates and sandstones and locally exist as (9) oriented concretions. Groundwater carbonates are best developed near the toes of the large, hanging-wall--derived alluvial fans, whereas phreatic cement preferentially exists in footwall-derived, alluvial-fan conglomerates. Pedogenic carbonate is distinguished from groundwater carbonate by the association with other diagnostic paleosol horizons, a predominantly vertical arrangement of root traces, peds, desiccation cracks, and calcic tubules, and by gradational contacts. The [[Delta].sup.13]C and [[Delta].sup.18]O values are similar among pedogenic and shallow groundwater carbonate, although locally nodules in eolian sand and gully-bed cement have higher [[Delta].sup.18]O values, perhaps due to the effects of evaporation. Some phreatic cements may be distinguished from pedogenic and shallow groundwater carbonate by lower values of [[Delta].sup.13]C and [[Delta].sup.18]O. Authigenic carbonate in footwall-derived, alluvial-fan sediment has consistently higher values of [[Delta].sup.13]C than that in hanging-wall--derived sediment, which may reflect differences in vegetative type and/or density on either side of the basin. Keywords: authigenesis, isotopes, paleosols, Pleistocene, Pliocene, Rio Grande rift.

The onshore central Corinth rift contains a syn-rift succession >3 km thick deposited in 5-15 kmwide tilt blocks, all now inactive, uplifted and deeply incised. This part of the rift records upward deepening from fluviatile to lake-margin conditions and finally to sub-lacustrine turbidite channel and lobe complexes, and deep-water lacustrine conditions (Lake Corinth) were established over most of the rift by 3.6 Ma. This succession represents the first of two phases of rift development - Rift 1 from 5.0-3.6 to 2.2-1.8 Ma and Rift 2 from 2.2-1.8 Ma to present. Rift 1 developed as a 30 kmwide zone of distributed normal faulting. The lake was fed by four major N- to NE-flowing antecedent drainages along the southern rift flank. These sourced an axial fluvial system, Gilbert fan deltas and deep lacustrine turbidite channel and lobe complexes. The onset of Rift 2 and abandonment of Rift 1 involved a 30 km northward shift in the locus of rifting. In the west, giant Gilbert deltas built into a deepening lake depocentre in the hanging wall of the newly developing southern border fault system. Footwall and regional uplift progressively destroyed Lake Corinth in the central and eastern parts of the rift, producing a staircase of deltaic and, following drainage reversal, shallow marine terraces descending from >1000 m to present-day sea level. The growth, linkage and death of normal faults during the two phases of rifting are interpreted to reflect self-organization and strain localization along co-linear border faults. In the west, interaction with the Patras rift occurred along the major Patras dextral strike-slip fault. This led to enhanced migration of fault activity, uplift and incision of some early Rift 2 fan deltas, and opening of the Rion Straits at ca. 400-600 ka. The landscape and stratigraphic evolution of the rift was strongly influenced by regional palaeotopographic variations and local antecedent drainage, both inherited from the Hellenide fold and thrust belt. [ABSTRACT FROM AUTHOR]