Basal Deposits Research Articles

Genetic removal of Nlrp3 protects against sporadic and R345W Efemp1-induced basal laminar deposit formation.

Chronic, unresolved inflammation has long been speculated to serve as an initiating and propagating factor in numerous neurodegenerative diseases, including a leading cause of irreversible blindness in the elderly, age-related macular degeneration (AMD). Intracellular multiprotein complexes called inflammasomes in combination with activated caspases facilitate production of pro-inflammatory cytokines such as interleukin 1 beta. Specifically, the nucleotide-binding oligomerization (NOD)-like receptor protein 3 (NLRP3) has received heightened attention due to the wide range of stimuli to which it can respond and its potential involvement in AMD. In this study, we directly tested the role of Nlrp3 and its downstream effector, caspase 1 (Casp1) in mediating early AMD-like pathology (i.e., basal laminar deposits [BLamDs]) in wild-type (WT) mice and the Malattia Leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD) mouse model (p.R345W mutation in Efemp1). Compared to aged-matched controls, R345W +/+ knockin mice demonstrated increased Muller cell gliosis, subretinal Iba-1 + microglial cells, higher Nlrp3 immunoreactivity in the retina, as well as significant transcriptional upregulation of complement component 3, Nlrp3, pro-Il1b, pro-caspase-1, and tissue inhibitor of matrix metalloproteinase 3 in the retinal pigmented epithelium (RPE)/choroid. These findings were accompanied by an age-related increase in BLamD formation in the R345W +/+ mice. Genetic elimination of either Nlrp3 or Casp1 significantly reduced both the size and coverage of BLamDs in the R345W +/+ background, highlighting an important and underappreciated pathway that could affect ML/DHRD onset and progression. Moreover, Nlrp3 knockout reduced spontaneous, idiopathic BLamDs in WT mice, suggesting translatability of our findings not only to rare inherited retinal dystrophies, but also potentially to AMD itself.

Review of type 3 macular neovascularization in age-related macular degeneration: no DRAMA (Deep Retinal Age-related Microvascular Anomalies).

Type 3 macular neovascularization (MNV) is a unique form of neovascular age-related macular degeneration (AMD) that presents distinct pathogenetic features, clinical manifestations, and prognostic considerations when compared to types 1 and 2 MNV. Insights gained from clinicopathological correlations, bridging in vivo examination techniques with ex vivo histological analysis, have significantly enhanced our comprehension of this MNV phenotype, shaped current management strategies and influenced future directions for therapeutics. The particularities of type 3 MNV, which may largely stem from its origin from the retinal vasculature, are critically important for predicting the disease course. Our current understanding suggests that type 3 MNV occurs in response to retinal pigment epithelium (RPE) disruption and photoreceptor loss when neovessels originating from the deep capillary plexus are accompanied by activated Müller glia as they infiltrate sub-retinal pigment epithelium basal laminar deposits. Dysregulation of angiogenic and angiostatic factors are thought to play a key role in its pathogenesis. The prognosis for type 3 MNV is likely bilateral involvement and progression towards macular atrophy. It may be imperative for practitioners to distinguish type 3 MNV from other mimicking pathologies such as intraretinal microvascular anomalies, which are also part of the type 3 disease spectrum. For instance, deep retinal age-related microvascular anomalies (DRAMA) may present with similar features on multimodal imaging yet may necessitate distinct management protocols. Distinguishing between these conditions may be vital for implementing tailored treatment regimens and improving patient outcomes in the diverse landscape of AMD phenotypes in the future.

Abetalipoproteinemia with angioid streaks, choroidal neovascularization, atrophy, and extracellular deposits revealed by multimodal retinal imaging

ABSTRACT Purpose Abetalipoproteinemia (ABL, MIM 200,100) is a rare autosomal recessive disorder caused by nonfunctional microsomal triglyceride transfer protein leading to absence of apolipoprotein B-containing lipoproteins in plasma and a retinitis pigmentosa-like fundus. The MTTP gene is expressed in retinal pigment epithelium (RPE) and ganglion cells of the human retina. Understanding ABL pathophysiology would benefit from new cellular-level clinical imaging of affected retinas. Methods We report multimodal retinal imaging in two patients with ABL. Case 1 (67-year-old woman) exhibited a bilateral decline of vision due to choroidal neovascularization (CNV) associated with angioid streaks and calcified Bruch membrane. Optical coherence tomography were consistent with basal laminar deposits and subretinal drusenoid deposits (SDD). Results Case 2 (46-year-old woman) exhibited unusual hyperpigmentation at the right fovea with count-fingers vision and a relatively unremarkable left fundus with 20/30 vision. The left eye exhibited the presence of nodular drusen and SDD and the absence of macular xanthophyll pigments. Conclusion We propose that mutated MTTP within the retina may contribute to ABL retinopathy in addition to systemic deficiencies of fat-soluble vitamins. This concept is supported by a new mouse model with RPE-specific MTTP deficiency and a retinal degeneration phenotype. The observed range of human pathology, including angioid streaks, underscores the need for continued monitoring in adulthood, especially for CNV, a treatable condition.

Luminescence dating of rock surfaces in challenging environments: The case of MIS5e gravelly transgressive lag deposit (Southern Sardinia, West Mediterranean Sea)

Determining the age of precise sea level markers such as marine terraces is often difficult because of the inherent limitation of traditional dating methods. A novel method based on Optical Stimulated Luminescence applicable to rock surfaces has been showing great promise in dating boulder and cobble surfaces from various environments. We performed Optically Stimulated Luminescence Rock Surface Dating (OSL RSD) on five cobbles from a basal transgressive lag deposit sealing a marine terrace referred to as the Last Interglacial (Marine Isotopic Stage 5e). We applied a consistent and highly selective 3-step acceptance criteria on five cobbles and obtained that only one was sufficiently well-bleached prior to burial. The resulting ages of 131 ± 8 ka and 127 ± 8 ka (obtained on 22 analyzed aliquots, n = 22) derived from the post-infrared infrared stimulated signal at 225oC (pIRIR225) and the preceding infrared stimulated signal at 50oC (pIR50/225), respectively, are consistent with each other as well as with the conventional luminescence age of ∼135 ka from the same sequence and with the U/Th age of ∼130 ka obtained from coral fragments. This work demonstrates that the RSD is a promising method for dating gravel veneer deposits overlaying marine terraces, enabling new chronologies for similar Quaternary deposits.

Palynological, tephra, and 14C records from southern Kaitoke, Great Barrier (Aotea) Island, New Zealand, since c. 30,000 cal. yr BP

ABSTRACT Here we present results of the last remaining three, unreported pollen and stratigraphic profiles from our previous investigations on Great Barrier Island from southern Kaitoke. The 14C and pollen data extend the island’s previous maximum pollen-vegetation date from c. 7000 cal. yr BP to close to the end of MIS 3 c. 30,000 cal. yr BP. The oldest 14C date (34,380-28,190 cal. yr BP) and the presence of secondary deposition fragments of Rotoehu Tephra in the basal brown sands and nearby dune deposits implies their formation between c. 30,000 and 45,000 yr BP. The basal sand deposits and palynology in Profile 1 indicate that the site was close to sea-level at the time. Subsequently, the sediments reflect the Last Glacial Coldest Period, characterised by increased Fuscospora pollen. Following the relative stability of the mid-Holocene high sea-level stand, alternations between drier and wetter (freshwater) conditions, with depositional hiatuses, are congruent with evidence for erratic sea-level falls causing blockage of coastal drainage and rear-dune flooding since c. 2,700 cal. yr BP; layers of preserved wood and in-situ stumps overlying firmer palaeosols were followed by fresh-water peats at two of the sites reported here and other, previously reported sites. Polynesian settlement and forest clearance occurs around the time of the 1314 ± 12 AD Kaharoa Tephra, consistent with the project’s previous reports, and with the timing from elsewhere in New Zealand.

Hyperautofluorescent material inside areas of macular atrophy may reveal non-lipofuscin fluorophores in late stage AMD.

To characterize fundus autofluorescence (FAF) in complete (cRORA) and incomplete retinal pigment epithelium and outer retinal atrophy (iRORA) by fluorescence lifetime imaging ophthalmology (FLIO). Overall, 98 macular atrophy (MA) lesions in 42 eyes of 37 age-related macular degeneration (AMD) patients (mean age: 80.9 ± 5.8 years), 25 of them classified as iRORA and 73 as cRORA by OCT, were investigated by FLIO in a short (SSC: 498-560 nm) and a long wavelength channel (LSC: 560-720 nm). Differences of FAF lifetimes and peak emission wavelength (PEW) between atrophic lesions and intact retinal pigment epithelium (RPE) in the outer ring of the ETDRS grid were considered. FAF lifetimes in MA were longer and PEW were significantly (p < 0.001) shorter than in intact RPE by 112 ± 78 ps (SSC), 91 ± 64 ps (LSC), 27 ± 18 nm (PEW) in iRORA and by 227 ± 112 ps (SSC), 167 ± 81 ps (LSC), and 54 ± 17 nm (PEW) in cRORA. 37% of iRORA and 24% of cRORA were hyperautofluorescent in SSC. Persistent sub-RPE-BL material in MA was newly found as a hyperautofluorescent entity with lifetimes considerably longer than that of drusen and RPE. Despite RPE and, thus, lipofuscin are greatly absent in MA, considerable FAF, preferably at short wavelengths, was found in those lesions. Drusen, persistent sub-RPE-BL material, basal laminar deposits, persistent activated RPE, and sclera were identified as putative sources of this fluorescence. FLIO can help to characterize respective fluorophores.

Topographic Measurement of the Subretinal Pigment Epithelium Space in Normal Aging and Age-Related Macular Degeneration Using High-Resolution OCT.

A micrometer scale hyporeflective band within the retinal pigment epithelium basal lamina - Bruch's membrane complex (RPE-BL-BrM) was topographically measured in aging and age-related macular degeneration (AMD). In a prospective cross-sectional study, 90 normal eyes from 76 subjects (range = 23-90 years) and 53 dry AMD eyes from 47 subjects (range = 62-91 years) were enrolled. Isotropic volume raster scans over 6mm × 6mm (500 × 500 A-scans) were acquired using a high-resolution (2.7 µm axial resolution) spectral-domain optical coherence tomography (SD-OCT) prototype instrument. Six consecutive optical coherence tomography (OCT) volumes were computationally motion-corrected and fused to improve feature visibility. A boundary regression neural network was developed to measure hyporeflective band thickness. Topographic dependence was evaluated over a 6-mm-diameter Early Treatment Diabetic Retinopathy Study (ETDRS) grid. The hyporeflective band thickness map (median of 4.3 µm and 7.8 µm in normal and AMD eyes, respectively) is thicker below and radially symmetric around the fovea. In normal eyes, age-associated differences occur within 0.7 to 2.3mm from the foveal center (P < 0.05). In AMD eyes, the hyporeflective band is hypothesized to be basal laminar deposits (BLamDs) and is thicker within the 3-mm ETDRS circle (P < 0.0002) compared with normal eyes. The inner ring is the most sensitive location to detect age versus AMD-associated changes within the RPE-BL-BrM. AMD eyes with subretinal drusenoid deposits (SDDs) have a significantly thicker hyporeflective band (P < 0.001) than those without SDDs. The hyporeflective band is a quantifiable biomarker which differentiates AMD from aging. Longitudinal studies are warranted. The hyporeflective band may be a useful biomarker for risk stratification and disease progression.

GSK3 inhibition reduces ECM production and prevents age-related macular degeneration-like pathology.

Malattia Leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD) is an age-related macular degeneration-like (AMD-like) retinal dystrophy caused by an autosomal dominant R345W mutation in the secreted glycoprotein, fibulin-3 (F3). To identify new small molecules that reduce F3 production in retinal pigmented epithelium (RPE) cells, we knocked-in a luminescent peptide tag (HiBiT) into the endogenous F3 locus that enabled simple, sensitive, and high-throughput detection of the protein. The GSK3 inhibitor, CHIR99021 (CHIR), significantly reduced F3 burden (expression, secretion, and intracellular levels) in immortalized RPE and non-RPE cells. Low-level, long-term CHIR treatment promoted remodeling of the RPE extracellular matrix, reducing sub-RPE deposit-associated proteins (e.g., amelotin, complement component 3, collagen IV, and fibronectin), while increasing RPE differentiation factors (e.g., tyrosinase, and pigment epithelium-derived factor). In vivo, treatment of 8-month-old R345W+/+ knockin mice with CHIR (25 mg/kg i.p., 1 mo) was well tolerated and significantly reduced R345W F3-associated AMD-like basal laminar deposit number and size, thereby preventing the main pathological feature in these mice. This is an important demonstration of small molecule-based prevention of AMD-like pathology in ML/DHRD mice and may herald a rejuvenation of interest in GSK3 inhibition for the treatment of retinal degenerative diseases, including potentially AMD itself.

Basal Linear Deposit: Normal Physiological Ageing or a Defining Lesion of Age-Related Macular Degeneration?

Objective: To determine if basal linear deposit (BLinD) is a specific lesion of age-related macular degeneration (AMD). Methods: The cohort was selected from a clinically and histopathologically validated archive (Sarks Archive) and consisted of 10 normal eyes (age 55-80 years) without any macular basal laminar deposit (BLamD) (Sarks Group I) and 16 normal aged eyes (age 57-88 years) with patchy BLamD (Sarks Group II). Only eyes with in vivo fundus assessment and corresponding high-resolution transmission electron microscopy (TEM) micrographs of the macula were included. Semithin sections and fellow-eye paraffin sections were additionally examined. BLinD was defined as a diffuse layer of electron-lucent vesicles external to the retinal pigment epithelium (RPE) basement membrane by TEM and was graded as follows: (i) Grade 0, absence of a continuous layer; (ii) Grade 1, a continuous layer up to three times the thickness of the RPE basement membrane (0.9 µm); (iii) Grade 2, a continuous layer greater than 0.9 µm. Bruch's membrane (BrM) hyalinisation and RPE abnormalities were determined by light microscopic examination of corresponding semithin and paraffin sections. Results: BLinD was identified in both normal (30%) and normal aged (62.5%) eyes. BLinD was thicker in normal aged eyes (p = 0.045; 95% CI 0.04-3.4). BLinD thickness positively correlated with both the degree of BrM hyalinisation (p = 0.049; 95% CI 0.05-2.69) and increasing microscopic RPE abnormalities (p = 0.022; 95% CI 0.188-2.422). RPE abnormalities were more likely to be observed in eyes with increased BrM hyalinisation (p = 0.044; 95% CI 0.61-4.319). Conclusions: BLinD is most likely an age-related deposit rather than a specific lesion of AMD. Its accumulation is associated with increasing BrM hyalinisation and microscopic RPE abnormalities, suggesting a relationship with dysregulated RPE metabolism and/or transport.

The "triple-layer sign": an optical coherence tomography signature for the detection of non-exudative macular neovascularization.

To assess the sensitivity and specificity of the "triple layer sign" (TLS) (retinal pigment epithelium (RPE), neovascular tissue, and Bruch's membrane) on structural optical coherence tomography (OCT) images for the diagnosis of treatment-naïve non-exudative type-1 macular neovascularization (NE-MNV) in age-related macular degeneration (AMD). Cross-sectional study. Two masked retinal experts evaluated the presence of the TLS in eyes with NE-MNV and controls with an RPE elevation without exudation due to other causes than NE-MNV in AMD [e.g., medium-large drusen, cuticular drusen, basal laminar deposits (BlamD)]. 130 eyes of 98 consecutive patients met the study criteria; 40 eyes of 40 patients satisfied the criteria for being included in the NE-MNV secondary to AMD group (27 females, 13 males, with a mean age of 73.8 ± 8.0years), and 90 eyes of 58 patients met the criteria to be included in the control group (31 eyes were included in the medium-to-large drusen sub-group, 32 eyes in the cuticular drusen sub-group, and 27 eyes in the BlamD group. The TLS was observed in 39/40 patients with NE-MNV and 8/90 controls. The sensitivity and specificity of the TLS for the diagnosis of NE-MNV were 97% and 91%, respectively. The TLS on OCT demonstrated high sensitivity and specificity values in detecting treatment-naive type 1 NE-MNV.

Age limits of basal deposits of the Upper Cambrian section of the Polar Urals according to the results of U-PB (LA-ICP-MS) zircon dating

Age limits of basal deposits of the Upper Cambrian section of the Polar Urals according to the results of U-PB (LA-ICP-MS) zircon dating

Structural OCT and OCT angiography biomarkers associated with the development and progression of geographic atrophy in AMD.

Geographic atrophy (GA) is an advanced, irreversible, and progressive form of age-related macular degeneration (AMD). Structural optical coherence tomography (OCT) and OCT angiography (OCTA) have been largely used to characterize this stage of AMD and, more importantly, to define biomarkers associated with the development and progression of GA in AMD. Articles pertaining to OCT and OCTA biomarkers related to the development and progression of GA with relevant key words were used to search in PubMed, Researchgate, and Google Scholar. The articles were selected based on their relevance, reliability, publication year, published journal, and accessibility. Previous reports have highlighted various OCT and OCTA biomarkers linked to the onset and advancement of GA. These biomarkers encompass characteristics such as the size, volume, and subtype of drusen, the presence of hyperreflective foci, basal laminar deposits, incomplete retinal pigment epithelium and outer retinal atrophy (iRORA), persistent choroidal hypertransmission defects, and the existence of subretinal drusenoid deposits (also referred to as reticular pseudodrusen). Moreover, biomarkers associated with the progression of GA include thinning of the outer retina, photoreceptor degradation, the distance between retinal pigment epithelium and Bruch's membrane, and choriocapillaris loss. The advent of novel treatment strategies for GA underscores the heightened need for prompt diagnosis and precise monitoring of individuals with this condition. The utilization of structural OCT and OCTA becomes essential for identifying distinct biomarkers associated with the initiation and progression of GA.

Research on the Mechanical Characteristics of Thick Alluvium on the Surface Subsidence Features of Thin Bedrock Deposits at Depth

Research on the Mechanical Characteristics of Thick Alluvium on the Surface Subsidence Features of Thin Bedrock Deposits at Depth

Rediscovering Age-Related Macular Degeneration with Swept-Source OCT Imaging: The 2022 Charles L. Schepens, MD, Lecture

Swept-source OCT angiography (SS-OCTA) scans of eyes with age-related macular degeneration (AMD) were used to replace color, autofluorescence, infrared reflectance, and dye-based fundus angiographic imaging for the diagnosis and staging of AMD. Through the use of different algorithms with the SS-OCTA scans, both structural and angiographic information can be viewed and assessed using both cross sectional and en face imaging strategies. Presented at the 2022 Charles L. Schepens, MD, Lecture at the American Academy of Ophthalmology Retina Subspecialty Day, Chicago, Illinois, on September 30,2022. Patients with AMD. Review of published literature and ongoing clinical research using SS-OCTA imaging in AMD. Swept-source OCT angiography imaging of AMD at different stages of disease progression. Volumetric SS-OCTA dense raster scans were used to diagnose and stage both exudative and nonexudative AMD. In eyes with nonexudative AMD, a single SS-OCTA scan was used to detect and measure structural features in the macula such as the area and volume of both typical soft drusen and calcified drusen, the presence and location of hyperreflective foci, the presence of reticular pseudodrusen, also known as subretinal drusenoid deposits, the thickness of the outer retinal layer, the presence and thickness of basal laminar deposits, the presence and area of persistent choroidal hypertransmission defects, and the presence of treatment-naïve nonexudative macular neovascularization. In eyes with exudative AMD, the same SS-OCTA scan pattern was used to detect and measure the presence of macular fluid, the presence and type of macular neovascularization, and the response of exudation to treatment with vascular endothelial growth factor inhibitors. In addition, the same scan pattern was used to quantitate choriocapillaris (CC) perfusion, CC thickness, choroidal thickness, and the vascularity of the choroid. Compared with using several different instruments to perform multimodal imaging, a single SS-OCTA scan provides a convenient, comfortable, and comprehensive approach for obtaining qualitative and quantitative anatomic and angiographic information to monitor the onset, progression, and response to therapies in both nonexudative and exudative AMD. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

PHENOTYPIC CHARACTERIZATION OF PREDICTORS FOR DEVELOPMENT AND PROGRESSION OF GEOGRAPHIC ATROPHY USING OPTICAL COHERENCE TOMOGRAPHY.

To evaluate the impact of optical coherence tomography phenotypes preceding atrophy related to age-related macular degeneration on the progression of atrophic lesions. In this observational retrospective cohort study, a total of 70 eyes of 60 consecutive patients with intermediate age-related macular degeneration with a minimum follow-up of 24 months were included. The atrophy was quantified using fundus autofluorescence, also considering the directionality of atrophy as centrifugal and centripetal progression rates. The main outcome measures were geographic atrophy (GA) progression rate (mm 2 /year) and square root transformation of GA (mm 2 /year). The best-fit model for GA (odds ratio: 1.81, P < 0.001) and square root transformation of GA (odds ratio: 1.36, P < 0.001) areas revealed that the main baseline predictor was the presence of a retinal pigment epithelium-basal lamina-Bruch membrane splitting. Large drusen at baseline appeared protective for the GA area lesion expansion over time (odds ratio: 0.52, P < 0.001) when considered with other confounders. A thin retinal pigment epithelium-basal lamina-Bruch membrane splitting without evidence of neovascularization on optical coherence tomography angiography likely represents an optical coherence tomography signature for late basal laminar deposits. Identifying this phenotype can help identify individuals with a higher risk of rapid progression and atrophy expansion.

Contrasting evolution of beach gold on two sides of an active orogen, Southern Alps, New Zealand

ABSTRACT Placer gold on beaches on either side of a major active mountain belt has strongly contrasting compositions and morphologies. Pleistocene-Holocene beach gold placers have formed along the West Coast where silver (Ag)-bearing gold has been eroded from mountains via steep rivers and glaciers, followed by rapid burial in the abundant associated coastal sediments. Deformation along transport pathways has produced flattened gold flakes, but some primary crystalline shapes are preserved. Internal deformation of particles has caused recrystallisation to fine-grained (µm scale) grain structures including mylonitic banding. However, only minor localised (µm scale) Ag leaching has occurred on some particle margins. In contrast, Pleistocene beach placers formed on the southern side of the mountains contain flattened gold particles with a complex transport history involving long-distance (hundreds of km) fluvial transport since Cretaceous. Most primary Ag has been leached from this gold during transport-related recrystallisation to fine (5–20 µm) internal grains. Sand-blasting on the southern beaches with low sediment supply has resulted in further deformation and leaching of Ag to form toroidal shapes with Ag-free delicate extremities. Placer gold which has undergone rapid transport and deposition is useful as a prospecting tool for bedrock deposits in glaciated terranes around the world.

Histologic and Immunohistochemical Characterization of GA-Like Pathology in the Rat Subretinal Sodium Iodate Model.

Geographic atrophy (GA) is an advanced form of dry age-related macular degeneration with multifactorial etiology and no well-established treatment. A model recapitulating the hallmarks would serve as a key to understanding the underlying pathologic mechanisms better. In this report, we further characterized our previously reported subretinal sodium iodate model of GA. Retinal degeneration was induced in rats (6-8weeks old) by subretinal injections of NaIO3 as described previously. Animals were sacrificed at 3, 8 and 12weeks after injection and eyes were fixed or cryopreserved. Some choroids were processed as flatmounts while other eyes were cryopreserved, sectioned, and immunolabeled with a panel of antibodies. Finally, some eyes were prepared for transmission electron microscopic (TEM) analysis. NaIO3 subretinal injection resulted in a well-defined focal area of retinal pigment epithelium (RPE) degeneration surrounded by viable RPE. These atrophic lesions expanded over time. RPE morphologic changes at the border consisted of hypertrophy, multilayering, and the possible development of a migrating phenotype. Immunostaining of retinal sections demonstrated external limiting membrane descent, outer retinal tubulation (ORT), and extension of Müller cells toward RPE forming a glial membrane in the subretinal space of the atrophic area. TEM findings demonstrated RPE autophagy, cellular constituents of ORT, glial membranes, basal laminar deposits, and defects in Bruch's membrane. In this study, we showed pathologic features of a rodent model resembling human GA in a temporal order through histology, immunofluorescence, and TEM analysis and gained insights into the cellular and subcellular levels of the GA-like phenotypes. Despite its acute nature, the expansion of atrophy and the GA-like border in this rat model makes it ideal for studying disease progression and provides a treatment window to test potential therapeutics for GA.

Geochemistry of the North Gondwana Paleozoic Araba and Naqus formation siliciclastics, Sinai: implications for provenance, paleoweathering, and tectonic setting

ABSTRACT The Araba and Naqus formations in Ras Milan, Sinai, constitute part of the major continuous Paleozoic clastic belt stretching across northern Gondwana. They are sandstone-dominated successions, resting on Precambrian granitic basement, with lowermost thin basal polymictic conglomerate deposits (1–2 m), marking the unconformity. The Araba Formation section is composed mainly of varicoloured violet to reddish brown, fine to coarse-grained laminated and planner and overturned cross-bedded sandstones, while the overlying Naqus Formation is characterized by chaotically distributed poorly sorted quartz pebbles to cobbles within a moderately-sorted coarse- to medium-grained quartz arenite and by abundance and variety of large-scale tabular and trough cross bedding. Modal QFL classification of Araba and Naqus formation sandstones revealed that they are merely quartzose sandstones (quartz arenites). Geochemistry of the succession shows extremely wide compositional ranges for almost all major elements, but the Araba Formation is relatively enriched in SiO2, TiO2, Fe2O3*, Na2O, P2O5, and depleted in Al2O3, MgO, CaO and K2O relative to Naqus Formation. Only the Araba Formation samples are depleted in the transition elements Ni, Cr and Co and oppositely possess extreme enrichment in the HFSEs (i.e. Zr, Hf, Y, Nb, Ta, Th, U), whereas both formations show variable depletion in the LILE Rb, K and Ba, and excessive REE abundances relative to the PAAS and UCC, and LREE-enriched patterns with marked negative Eu anomalies. The provenance of the Naqus and Araba formations could be an earlier felsic magmatic source, which has undergone extensive sedimentary recycling. They possess high compositional maturity and were subjected to intensive to moderate weathering during humid climatic conditions. Passive margin tectonic setting is implied which denotes the derivation of Araba and Naqus formation siliciclastics from stable continental regions or plate interiors and deposition in intracratonic basins.

Cu and Au Mineralization of the Tolparovo Ore Occurrence: Evidence for the Formation of Redbed Copper Occurrences in Neoproterozoic Deposits of the Southern Urals

The mineralization and geochemical features of the Tolparovo ore occurrence are studied to reveal the contribution of diagenetic and epigenetic processes in the formation of copper mineralization in redbed deposits. The methods of electron microscopy, ICP MS, X-ray fluorescence, X-ray phase, atomic absorption, thermogravimetric analyses, and C and O isotopic composition were used. The ore is confined to the fault zone and feathering dolomite–calcite veins, having formed at temperatures of ~330–200 °C and pressures of 0.8–0.2 kbar. Similar to other copper redbed occurrences of the Bashkirian uplift, the Tolparovo copper ore occurrence is confined to basal Neoproterozoic deposits. Siliciclastic and carbonate deposits of this level were accumulated at low paleoequator latitudes in arid climates of continental and coastal–marine environments close to evaporite ones. Rocks of this stratigraphic interval demonstrate increased background concentrations of copper (~2–5 times exceeding the clark), which explains the stratification of redbed copper ore occurrences, indicating a predominantly sedimentary copper source. However, most of the redbed copper ore occurrences of the Bashkirian uplift are located in tectonic zones and are associated with the dikes of the Inzer gabbrodolerite complex. This connects the generation of ore occurrences with the formation of the Southern Urals Arsha Large Igneous Province (707–732 Ma) and the activity of postmagmatic fluids. Magmatic processes were presumably activated due to the collapse of the Rodinia supercontinent. It is shown that copper mineralization in stratiform deposits may result from a joint manifestation of dia- and epigenesis processes.

Foraminiferal Biostratigraphy and Paleoecology of the Southeasternmost Outcrops of the Oligocene Qom Formation, SE Iran

Abstract The Qom Formation is deposited along more than 1800 km of the NE margin of the Tethyan Seaway in the Oligocene-Early Miocene during the final sea transgression on the Iranian Plate. We present (foraminiferal-based) biostratigraphic data from three exposed sections near the northwestern Jazmurian Lake, as the southeasternmost outcrops of the Qom Formation. Larger benthic foraminifera are mainly represented by nummulitids (Nummulites, Operculina, Heterostegina), lepidocyclinids (Nephrolepidina, Eulepidina, Lepidocyclina), and Amphistegina. The presence of Nummulites fichteli/intermedius and Nummulites vascus in the lower parts of the study sections together with lepidocyclinids indicates that their basal deposits could be attributed to the late Rupelian. The Qom Formation is of late Rupelian-Chattian in age in all three stratigraphic sections. Also, the presence of Nummulites- bearing tuffaceous limestones and tuff unit in the lower part of the Bozadan section is indicative of contemporaneous volcanic activity. Most parts of the study sections with an association of large and flat perforate foraminifera were deposited in normal saline waters. These parts are presented by large and flat nummulitids, lepidocyclinids, and Amphistegina. These large and flat perforate foraminifera often dominate in the lower part of the photic zone. The abundance of larger benthic foraminiferal and coralline red algae and the coral facies indicates a tropical-subtropical palaeoenvironment.