Red Clay Layer Research Articles

Late Maastrichtian and K/T paleoenvironment of the eastern Tethys (Israel): mineralogy, trace and platinum group elements, biostratigraphy and faunal turnovers

Abstract The late Maastrichtian to early Danian at Mishor Rotem, Israel, was examined based on geochemistry, bulk rock and clay mineralogies, biostratigraphy and lithology. This section contains four red clay layers of suspect impact or volcanic origin interbedded in chalk and marly chalks. PGE anomalies indicate that only the K/T boundary red layer has an Ir dominated PGE anomaly indicative of an impact source. The late Maastrichtian red clays have Pd dominated PGE anomalies which coincide with increased trace elements of terrigenous and volcanogenic origins. Deccan or Syrian-Turkey arc volcanism is the likely source of volcanism in these clay layers. Glauconite, goethite and translucent amber spherules are present in the clay layers, but the Si-rich spherules reported by Rosenfeld et al. [l989] could not be confirmed. The absence of Cheto smectite indicates that no altered impact glass has been present. The red layers represent condensed sedimentation on topographic highs during sea level highstands. In the Negev area, during the late Maastrichtian, the climate ranged from seasonally wet to more arid conditions during zones CF3 and CF2, with more humid wet conditions in the latest Maastrichtian zone CF1 and in the early Danian, probably linked to greenhouse conditions. Planktic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids. Times of intensified stress are indicated by the disaster opportunist Guembelitria blooms, which can be correlated to central Egypt and also to Indian Ocean localities associated with mantle plume volcanism. Marine plankton thus support the mineralogical and geochemical observations of volcanic influx and reveal the detrimental biotic effects of intense volcanism.

Do multiple cycles of aeolian deposit-pedogenesis exist in the reticulate red clay sections in southern China?

The Xiangyang reticulate red clay section was newly sampled in highresolution. The viewpoints different from the previous studies[1-7] are put forward after studying Munsell color values, weathering degrees, magnetic parameters and stable carbon isotopic compositions of the section. They are as follows: (1) The curves of hue, DCB extracted iron (Fed), DCB extracted iron/total iron ratio (Fed/Fet), weathering index (BA) of the section show that the redness is not significantly correlated with the weathering degree of the layers though the uppermost yellow-brown-colored layer is relatively weakly weathered. The variation in hues of the section is possibly attributed to the change of hematite and goethite contents. It is insufficient to determine the existence of the multiple deposit-pedogenesis cycles in the section, like the loess-paleosol sequence in Chinese Loess Plateau, only by the color variation. (2) Magnetic susceptibility (x) values in the non-reticulate and weakly reticulate layers are high; but are quite low in the reticulate red clay layer. The former are more than ten times higher than the latter because of the leaching and collapse of superparamagnetic (SP) and stable single domain (SSD) magnetic particles during the plinthitic processes. Hence,x values in the section are not controlled by weathering and pedogenic processes, and no longer have clear paleoclimatic implication. It is not correct to prove the existence of the multiple deposit-pedogenesis cycles in the section usingx curves. (3) The organic δ13 C curve of the section illustrates the reduction of forests and increasing of C4 plants in the study area since the late stage of the Quaternary period. It could not prove the existence of the multiple deposit-pedogenesis cycles in the section either. (4) As a matter of fact, it is difficult to prove the existence of the multiple deposit-pedogenesis cycles in the Xiangyang section like the loess-paleosol sequence in Chinese Loess Plateau using the evidence available currently.

Calcareous nannofossil biostratigraphy and paleoecology of the Cretaceous–Tertiary transition in the central eastern desert of Egypt

The Gebel Qreiya and nearby Wadi Hamama sections of the central Eastern Desert are among the most complete K/T boundary sequences known from Egypt. The two sections were analyzed spanning an interval from l.83 Myr below to about 3 Myr above the K/T boundary. A 1-cm-thick red clay layer at the K/T boundary at Gebel Qreiya contains an Ir anomaly of 5.4 ppb. The high-resolution study and well-preserved nannoflora provide good age control and the first quantitative records of calcareous nannofossil assemblages for paleoecological interpretations across the K/T transition in Egypt. Four zones ( Micula murus, Micula prinsii, NP1, and NP2) were distinguished and correlated with other nannofossil and planktonic foraminiferal zonations that are broadly applicable for the eastern Tethys region. Latest Maastrichtian assemblages are abundant and diverse, though Cretaceous species richness progressively decreased across the K/T boundary. Dominant species include Arkhangelskiella cymbiformis, Micula decussata and Watznaueria barnesae, with high abundance of dissolution-resistant M. decussata reflecting periods of high environmental stress. Thoracosphaera blooms mark the K/T boundary and are followed by an acme of the opportunistic survivor Braarudosphaera bigelowii, the first appearance of the new Tertiary species Cruciplacolithus primus, and an acme of Coccolithus cavus/ pelagicus. These successive abundance peaks provide the basis for subdivision of the Early Danian Zones NP1 and NP2 into five subzones. Correlation of selected nannofossil taxa from the Egyptian sections with those from various onshore marine and deep-sea sections provides insights into their paleoenvironmental and paleoecological affinities.

High-stress paleoenvironment during the late Maastrichtian to early Paleocene in Central Egypt

Biostratigraphic, mineralogical, geochemical and isotopic analyses of the Gebel Qreiya section in the Asyut Basin of central Egypt indicate a depositional environment interrupted by periods of erosion due to local tectonic activity exacerbated by eustatic sea-level fluctuations, and by high-stress environmental conditions akin to those normally experienced during the Cretaceous–Tertiary boundary transition. During the late Maastrichtian (66.8–65.4 Ma) this region experienced a breakdown of the biologically mediated surface to bottom gradient of the 13C/ 12C ratio with planktic δ 13C values 0.2–0.8‰ lighter than benthic values. Planktic foraminiferal species diversity was reduced by more than 50%, with faunal assemblages dominated (75–90%) by the opportunistic disaster species Guembelitria cretacea, which alternate with abundance of small, low oxygen-tolerant heterohelicids ( Heterohelix navarroensis, H. dentata, H. globulosa). This prolonged breakdown in ocean primary productivity occurred during a time of global climate cooling and sea-level regressions (at 66.8 and 65.5 Ma), though clay mineralogy suggests that locally low seasonality warm, wet, tropical and subtropical conditions prevailed. The high detrital influx suggests that the biologically high-stress environment was primarily linked to the existing shallow shelf conditions in southern Egypt, and possibly to local tectonic activity and restricted circulation. A normal carbon isotope gradient was briefly re-established during the short climate warming and rising sea level between 65.4 and 65.2 Ma, a time of increased species diversity, peak abundance of rugoglobigerinids and common heterohelicids. During the last 200 000 years of the Maastrichtian, increased precipitation and terrestrial runoff (increased phyllosilicates and kaolinite) and increasing total organic carbon values are associated with Heterohelix-dominated planktic foraminiferal assemblages. The K/T boundary is marked by a red clay layer and Ir anomaly of 5.4 ppb. During the early Danian, planktic foraminiferal populations and stable isotope data indicate that similarly fluctuating high-stress conditions prevailed in central Egypt as elsewhere in the marginal eastern Tethys.

Origin of red clay layers interbedded with basalts of the Golan Heights

Red clay layers interbedded with basalt flows of Pleistocene age in the Golan Heights have been described and sampled for analyses. Data for these layers have been compared with those for modern soils of the locality. Because the layers have pedogenic features and most also contain quartz of assumed aeolian origin, they are considered to by paleosols even though they are low in organic matter. Smectite is the dominant clay mineral in the paleosols, as it is in modern soils of the area. At the same time, minerals characteristic of hydrothermal activities are absent. Low proportions of kaolinite as compared to those of modern soils are attributed to weathering under a drier climate in the Middle Pleistocene (approximately 0.7–1.6 m.y. B.P.) than that of the present. The paleosols are dense, have strong columnar structure and have well expressed mangans. These features, as well as the dehydration of iron oxides, are attributed to contacts with molten rock that become the basalt flows.

GENESIS OF RED AND BLACK SOILS ON BASALT ON THE DARLING DOWNS, QUEENSLAND, AUSTRALIA

SummaryShallow friable red soils (euchrozems) and shallow cracking clays (black earths) occur in close proximity on basalt hills of the Darling Downs of Queensland. The euchrozems are mainly restricted to fiat hill crests and are associated with lithosols; the shallow black earths occur on upper pediment slopes, on small convex crests and on depressions on flat crests. The euchrozems are moderately leached and contain kaolin minerals and hematite with minor montmorillonite, while the black earths are dominantly montmorillonite with minor kaolin and hematite. It is proposed that the euchrozems have developed by long continued weathering under stable well‐drained conditions while the black earths have formed in sites prone to erosion and in situations with less water available for weathering. The weathering products produced in each situation have ensured continuation of the processes. The presence of two red soils in anomalous positions have been ascribed to (a) soil formation on exposed ‘bole’ (compacted red clay) layers and (b) local peculiarities of parent material controlling the course of weathering.