Geologica Acta最新文献

{"title":"Distribution and provenance of heavy minerals from recent sediments of Green Lake, North Brazil, revisited","authors":"A. C. S. Ribeiro, L. O. Santos, Paulo Cerqueira Dos Santos, R. M. Almeida, R. Mendes, A. Mendes","doi":"10.1344/geologicaacta2022.20.5","DOIUrl":"https://doi.org/10.1344/geologicaacta2022.20.5","url":null,"abstract":"Geostatistical and multivariate statistical analyses were applied to heavy mineral data from an Amazonian fluvial-lake system near the Tapajós River mouth to investigate the spatial distribution and source-area of sediments. Twenty-one points were investigated, and the physical characteristics of the Green Lake deepest point were determined. Sand accumulates in the lake margins and mud quantity increases towards the lake center. Heavy mineral assemblage is composed of zircon, tourmaline, kyanite, rutile, staurolite, anatase, sillimanite, garnet, and spinel. Tourmaline, staurolite, and spinel are more abundant in the southeast area of the lake, while kyanite is dominant in the north area and zircon is in the whole lake except in its southeast area. Zircon - tourmaline and zircon - staurolite pairs are negatively correlated (r= -0.947 and -0.775, respectively), while tourmaline - staurolite and sillimanite - anatase pairs have a positive correlation (r= 0.628 and 0.675, respectively) which indicate different source rock types. Geostatistical analysis grouped the heavy minerals in three grups: Group 1 (tourmaline – staurolite – spinel - kyanite) and Group 2 (garnet – rutile – sillimanite - anatase) related to metamorphic source rocks ranging from medium to high grade, and Group 3 (zircon) related to acid igneous source rocks. The heavy mineral assemblage of Green Lake is analogous to the assemblage of the Alter do Chão Formation, indicating that this formation is the source of sediments of Green Lake.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49192588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neotectonics of Turkey (Türkiye) and surrounding regions: a new perspective with block modelling","authors":"G. Seyitoğlu, B. Aktuğ, Korhan Esat, B. Kaypak","doi":"10.1344/geologicaacta2022.20.4","DOIUrl":"https://doi.org/10.1344/geologicaacta2022.20.4","url":null,"abstract":"This paper aims to present a new neotectonic perspective concordant with the seismic activities in Turkey and surrounding regions. The neotectonic structures have been re-evaluated mainly by using focal mechanism solutions and high-resolution satellite (Google Earth) images. The Southeast Anatolian Wedge explains thrust/blind thrust and asymmetrical folding relationship in SE Turkey, Syria, and Northern Iraq. The neotectonic structures of the Turkish-Iranian Plateau are enlightened by the rhomboidal cell model which creates a base to determine multiple intersection points between the region-wide left- and right-lateral shear zones. The releasing stepover between the North Anatolian Fault Zone and Southeast Anatolian-Zagros Fault Zone plus their connections with the Northeast Anatolian Fault Zone and the East Anatolian Fault Zone are described in a more meaningful way with the Anatolian Diagonal concept. It also clarifies the role of left-lateral shear zone in the west-southwest movement of Anatolian plate and its relationship with the Aegean and Cyprus arcs. A neotectonic region under the influence of NW-SE contraction is determined between the North Anatolian, Eskişehir, and Kırıkkale-Erbaa fault zones in which the Elmadağ-Eldivan and Abdüsselam pinched crustal wedges and the Beypazarı Blind Thrust Zone are developed. A new route for the southern branch of the North Anatolian Fault Zone is determined between Bolu and Değirmenlik (Milos) Island in the Aegean Sea via Mudurnu, Bursa, Balıkesir, and İzmir. All main neotectonic structures mentioned in this paper are evaluated by the elastic dislocation modelling and new neotectonic provinces are suggested.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46261754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new elasmobranch fauna from the early Miocene of Sharbithat (Sultanate of Oman) reveals the teeth of an ancient fantail stingray","authors":"V. Charpentier, S. Adnet","doi":"10.1344/geologicaacta2022.20.2","DOIUrl":"https://doi.org/10.1344/geologicaacta2022.20.2","url":null,"abstract":"Here we describe a new elasmobranch assemblage consisting of isolated dental material from the Aquitanian near-shore marine deposits of the Shuwayr and Warak formations at Sharbithat, in eastern Sultanate of Oman. The faunal composition clearly indicates affinities to other early Miocene elasmobranch-bearing localities worldwide. This assemblage is predominantly composed of large and common pelagic sharks as well as teeth attributable to a new species of fantail stingray, Taeniurops tosii, as old as the oldest undisputable fossil records of Taeniurops. The study of this fossil assemblage presented here improves the knowledge of the ancient elasmobranchs that frequented the eastern Arabian coasts during the closure of the Neotethys and the birth of the Arabian Sea.\u0000DOI: 10.1344/GeologicaActa2022.20.2","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45784148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The paleoecology and depositional model of the Oligo-Miocene coral reefs in the Mohammad Abad Area, the west of Baft, SW Kerman, Iran","authors":"Fatemeh Hosseinipour","doi":"10.1344/geologicaacta2022.20.1","DOIUrl":"https://doi.org/10.1344/geologicaacta2022.20.1","url":null,"abstract":"This paper deals with the Oligo-Miocene coral reefs in the Mohammadabad Area, W Baft, SW Kerman. The studied coral reefs include 11 families, 25 genera and 33 species of the scleractinian corals. The coral reef successions have deposited in three cycles on a mixed siliciclastic-carbonate platform. To understanding the paleoecology, reef architecture and depositional model of studied reefal successions, statistical analyses based on the coral niches, sedimentology analyses based on the grain size of the marly strata and microfacies analyses on limestone strata have used. Based on the statistical analyses, the coral community includes eight ecotypes. The distribution of these ecotypes indicates that, despite of various thicknesses, in all three coral reef successions, the branching and fast growth ecotypes are present at the basal parts and the massive, placoid and meandroid colonies are recorded in the slope, crest and distal parts of the reefs. The main disruptive phenomenon that stopped the reef development and affected the reef architecture has been the addition of clastic deposits to the carbonate system. This sediment load increase is recorded as marly strata. By The addition of clastic sediment load to the system, the carbonate content of the system has diluted, the salinity, water transparency and photic level is decreased, the favorable attachment hard substrate for coral polyps is limited, the nutrient and oxygen flux is disrupted and the coral reefs are suffocated.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48086802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The enriched Variscan lithosphere of NE Iberia: data from postcollisional Permian calc-alkaline lamprophyre dykes of Les Guilleries","authors":"Esteban Mellado, M. Corbella, Didac Navarro, Andrew R. C. Kylander","doi":"10.1344/geologicaacta2021.19.15","DOIUrl":"https://doi.org/10.1344/geologicaacta2021.19.15","url":null,"abstract":"Post-collisional mafic dykes crosscut the Paleozoic metamorphic basement and late-Variscan plutons in Les Guilleries massif (Catalan Coastal Ranges, NE Iberia). The predominance of mafic phenocrysts, porphyritic texture, abundant amphibole, high MgO and volatile content, together with crustal-like trace-element patterns indicate that the dykes correspond to calc-alkaline lamprophyres, mainly spessartites. Their enrichment in LILE, HFSE and REE and initial Sr-Nd isotopic compositions (87Sr/86Sri between 0.70851 and 0.71127, epsilon Ndi between -5.23 and -4.63) are consistent with an enriched subcontinental lithospheric mantle source. U-Pb ages of matrix titanite crystals yield concordia ages of 262±7Ma, congruent with crosscutting relationships. Postmagmatic processes are evidenced by intense chloritization and albitization of the lamprophyres, together with systematic variations of Na2O vs SiO2, K2O, CaO, Ba, Rb, Cs, Pb, Sr, Tl, and Zn, and possibly the removal of F. The geochemical and geochronological data support an orogenic geochemical affinity, in accordance with the transitional tectonic regime between Variscan compression/transpression and post-collisional transtension/extension, related to the fragmentation of Pangea and thinning of the lithosphere. The lamprophyre dykes studied could represent the youngest pulse of Variscan orogenic magmatism and, therefore, mark its end in NE Iberia before the onset of the generalized Triassic extension.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66405600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbon and oxygen stable isotope record of upper Kimmeridgian shallow-marine ramp carbonates (Iberian Basin, NE Spain): the imprint of different burial and tectonic histories","authors":"C. Sequero, G. Della Porta, B. Bádenas, M. Aurell","doi":"10.1344/geologicaacta2021.19.14","DOIUrl":"https://doi.org/10.1344/geologicaacta2021.19.14","url":null,"abstract":"Bulk carbon and oxygen stable isotopes of ancient shallow-marine carbonates can record the effects of multiple palaeoenvironmental factors, but also the imprint of several post-depositional processes, which may alter the original marine isotopic composition. In this study, carbon and oxygen stable isotope analyses were performed on bulk carbonate, bivalve calcitic-shell (Trichites) and calcite vein samples from two stratigraphic sections (Tosos and Fuendetodos, present-day distance 15km), representing proximal inner- and distal mid-ramp environments, respectively, of the uppermost Kimmeridgian ramp facies deposited in the northern Iberian Basin (NE Spain). These successions underwent different diagenetic pathways that altered the primary marine isotopic composition in each section in different ways. Different burial histories, tectonic uplift and a variable exposure to meteoric diagenesis from the end of the Kimmeridgian to the Cenozoic (following Alpine tectonic uplift) are reflected in the different alteration patterns of the carbon and oxygen stable isotope signatures. A significant deviation to lower values in both δ13O and δ18O is recorded in those carbonates mostly exposed to meteoric diagenesis (distal mid-ramp Fuendetodos section), because of post-depositional tectonic uplift (telogenesis). On the other hand, the deposits mainly affected by burial diagenesis (proximal inner-ramp Tosos section) only record low δ18O with respect to expected values for pristine Kimmeridgian marine carbonates. The different burial and tectonic uplift histories of these deposits in each sector, due to their different tectonic evolution in this part of the basin, resulted in a variable degree of diagenetic resetting. However, in spite of the different diagenetic resetting reported of the carbon and oxygen stable isotope signatures in each section, these carbonates show similar cement types in termsof fabrics and cathodoluminescence properties. The diagenetic resetting reported for these carbonates prevents the use of the δ13O and δ18O records for addressing palaeoenvironmental interpretations, but instead highlights useful features regarding the variable diagenetic overprint of the studied shallow-marine carbonate successions concerning their specific post-depositional history.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49110343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pliocene marine Bivalvia of Vale do Freixo (Pombal, Portugal): updated taxonomic list and discussion","authors":"R. Pimentel, P. Callapez, P. Legoinha","doi":"10.1344/geologicaacta2021.19.13","DOIUrl":"https://doi.org/10.1344/geologicaacta2021.19.13","url":null,"abstract":"The exceptional Pliocene marine faunal assemblages of west central Portugal have been known since the late 19th century. They include highly diverse molluscan faunas whose study is far to be completed. Discovered nearly 40 years ago, Vale do Freixo (Carnide, Pombal) is perhaps the most outstanding fossil site. Neverthless, the bivalves remain relatively unknown. This study focuses on the taxonomy of this relevant group of marine Mollusca. The research, based on a detailed sampling of three fossiliferous beds from the Carnide Formation, yielded a list of 85 species belonging to 75 genera and 32 families. Forty-three species are new for the Carnide area and twenty-three are reported for the first time in the Portuguese Pliocene, increasing to 115 the number of known species in the Mondego Basin in the Beira Litoral.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42352804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Post-rift extensional tectonics at the edge of a carbonate platform: insights from the Middle Jurassic-Early Cretaceous Monte Giano stratigraphic record (central Apennines, Italy)","authors":"F. Capotorti, C. Muraro","doi":"10.1344/geologicaacta2021.19.12","DOIUrl":"https://doi.org/10.1344/geologicaacta2021.19.12","url":null,"abstract":"A new interpretation of the Middle Jurassic-Early Cretaceous paleogeographic evolution of the NW sector of the Latium-Abruzzi carbonate platform facing the Umbria-Marche Basin is proposed, based on Monte Giano area (central Apennines, Italy). During Late Triassic-early Bajocian time, the area was characterized by shallow water sedimentation. Inner and marginal carbonate platform deposits are overlain by pelagic deposits (Posidonia level), early Bajocian p.p. in age. This unconformity testifying the sudden drowning of the Monte Giano area, while shallow water sedimentation persisted in the remaining sectors of the carbonate platform. The Posidonia level is paraconformably overlain by distal slope deposits of the Velino Gorge limestones Formation, Kimmeridgian p.p.-Tithonian p.p. in age. Therefore, a 12Ma gap is recorded as in the Umbria-Marche Basin pelagic carbonate platforms. An extensional Bajocian tectonic phase, possibly related to the Piemont-Ligurian Ocean opening coupled with rheologic differences at the basin/platform boundary, drastically changed the regional paleogeography causing the breakup and the drowning of the NW sector of the Latium-Abruzzi carbonate platform and the creation of a large flat-topped pelagic carbonate platform. The estimate offset of the early Bajocian fault is around 300-350m. The Velino Gorge limestones fm. pass laterally and vertically to the Upper Tithonian platform-margin reef complex of the Ellipsactinia limestones fm.; these units constitute a shallowing and coarsening upward sequence and levelled the paleobathymetric gradient created by the Bajocian extension. The progradation of the Latium-Abruzzi carbonate platform continued during Early Cretaceous time. These results have strong implications on the tectonic and paleogeographic evolution of the major domains of the central Apennines.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45653379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crandallite-rich beds of the Libkovice Member, Most Basin, Czech Republic: climatic extremes or paleogeographic changes at the onset of the Miocene Climatic Optimum?","authors":"K. Mach, V. Rapprich, M. Faměra, M. Havelcová, T. Matys Grygar, T. Novotný, M. Rehor, Yulia V. Erban Kochergina","doi":"10.1344/geologicaacta2021.19.11","DOIUrl":"https://doi.org/10.1344/geologicaacta2021.19.11","url":null,"abstract":"We describe the occurrence and possible origin of rare beds 1–10cm thick and containing 20–70% of crandallite, a Ca-Al phosphate enriched in Sr and Ba, found within otherwise monotonous clay-rich lacustrine sediments of the Most Basin in the Central-European Neogene Ohře Rift system. The beds were formed at ca. 17.31, 17.06, and 16.88Ma, while the entire suite of monotonous clays of the Libkovice Member was deposited between 17.46 and 16.65Ma. Trace-element and organic geochemistry, Ar-Ar geochronology and C-O-Sr isotope systematics are used to infer their source and processes leading to their formation. The most enigmatic aspect of the formation of the crandallite beds is the removal of a huge amount of phosphorus from its biogenic cycle in the lacustrine system, which was otherwise stable for ca. 0.8My. Formation of detritus-poor crandallite beds could result from some exceptional environmental disruptions that hindered transport of fine clastic material to the basin floor. Silicic volcanic activity in the area of the Pannonian Basin could have triggered this disruption. Crandallite could provide evidence of long-lasting droughts and acidification of the exogenic environment, as they are roughly coeval with the onset of the Miocene Climatic Optimum at ca. 17.0Ma.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42686060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Critical analysis of Mediterranean sea level limit cycles during the Messinian salinity crisis","authors":"M. Baum","doi":"10.1344/GeologicaActa2021.19.10","DOIUrl":"https://doi.org/10.1344/GeologicaActa2021.19.10","url":null,"abstract":"The Messinian Salinity Crisis (5.97-5.33Ma) may be one of the most significant periods of sea-level change in recent geologic history. During this period, evaporite deposition throughout the Mediterranean basin records a series of dramatic environmental changes as flow through the Strait of Gibraltar was restricted. In the first stage of evaporite deposition, cycles of gypsum appear in shallow basins on the margins of the Mediterranean. The complex environmental history giving rise to these cycles has been investigated for decades but remains controversial. Notably, whether the evaporites are connected to significant changes in Mediterranean sea level is an open question.\u0000In one proposed model, competition between tectonic uplift and erosion at the Strait of Gibraltar gives rise to selfsustaining sea-level oscillations—limit cycles—which trigger evaporite deposition. Here I show that limit cycles are not a robust result of the proposed model and discuss how any oscillations produced by this model depend on an unrealistic formulation of a key model equation. First, I simplify the model equations and test whether limit cycles are produced in 64 million unique combinations of model parameters, finding oscillations in only 0.2% of all simulations. Next, I examine the formulation of a critical model equation representing stream channel slope over the Strait of Gibraltar, concluding that a more realistic formulation would render sea-level limit cycles improbable, if not impossible, in the proposed model.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45061132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}