Immigration of the Genus Macrocephalites Spath and The
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Or Early Callovian) Ammonites from Alaska and Montana
Jurassic (Bathonian or Early Callovian) Ammonites From Alaska and Montana By RALPH W. IMLAY SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 374-C Descr$tions and illustrations of ctphalopods of possible late Middle Jurasric (Bathonian) age UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1962 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. CONTENTS Page Page C- 1 Age of the faunas-Continued C- 1 Callovian versus Bathonian in Greenland- - - - _ - - _ - - C-2 Callovian versus Bathonian in Alaska and Montana- -- - Stratigraphic summary- __ --______ _ - - - -- - ---.- -- -.- - - C-2 Paleogeographic considerations- - -_-- -- ---- ---- Cook Inlet region, Alaska -______--------.-.--..--c-2 Summation of the evidence- - - _._ _ - _ _ - - - - - - - - - - - - Iniskin Peninsula-_-_______----.--------~.--C-2 Comparisons with other faunas---------___----------- Peninsula north of Chinitna Bay----- __._ _ _._ - C-3 \Vestern interior of Canada- - - -- -- -____------- --- Talkeetna Mountains ----___-_ - - -- ---- - - -- - -- C-3 Arctic region-_-_---___-_----------------------- Western Montana- - -----__-----------------.---C-5 other regions--__-__-____----------------------- Rocky Mountain front north of the Sun River- (2-5 Geographic distribution ___-___ --- - ---------- ------ -- - Drummond area--- ---_____ _--- -- -.-- ---- -- - C-10 Summary of results- --_-____-_----_---_-_----------- Age ofthe faunas-----------_----------------------- GI0 Systematic descriptions--_ _ _ - _ - - - - - - - - - - - - - - - - - - - - - - - Evidence from Alaska---____________--------------C-10 Literature cited _-_-_---______----------------------- Evidence from Montana --_-_____ --- - - -- .--- --- - - C-12 Index---__--___-_-_------------------------------- ILLUSTRATIONS [Plates 1-3 follow index] PLATE 1. Holcophylloceras, Oecotraustes (Paroecotraustes) ?, and Arctocephalites (Cranocephalites). 2. -
The Middle Jurassic of Western and Northern Europe: Its Subdivisions, Geochronology and Correlations
The Middle Jurassic of western and northern Europe: its subdivisions, geochronology and correlations John H. Callomon The palaeogeographic settings of Denmark and East Greenland during the Middle Jurassic are outlined. They lay in the widespread epicontinental seas that covered much of Europe in the post-Triassic transgression. It was a period of continuing eustatic sea-level rise, with only distant connections to world oceans: to the Pacific, via the narrow Viking Straits between Greenland and Norway and hence the arctic Boreal Sea to the north; and to the subtropical Tethys, via some 1200 km of shelf-seas to the south. The sedimentary history of the region was strongly influenced by two factors: tectonism and climate. Two modes of tectonic movement governed basinal evolution: crustal extension lead- ing to subsidence through rifting, such as in the Viking and Central Grabens of the North Sea; and subcrustal thermal upwelling, leading to domal uplift and the partition of marine basins through emergent physical barriers, as exemplified by the Central North Sea Dome with its associated volcanics. The climatic gradient across the 30º of temperate latitude spanned by the European seas governed biotic diversity and biogeography, finding expression in rock-forming biogenic carbonates that dominate sediments in the south and give way to largely siliciclastic sediments in the north. Geochronology of unrivalled finesse is provided by standard chronostratigraphy based on the biostratigraphy of ammonites. The Middle Jurassic saw the onset of considerable bioprovincial endemisms in these guide-fossils, making it necessary to construct parallel standard zonations for Boreal, Subboreal or NW European and Submediterranean Provinces, of which the NW European zonation provides the primary international standard. -
Callovian (Middle Jurassic) Dinoflagellate Cysts from the Algarve Basin, Southern
1 Callovian (Middle Jurassic) dinoflagellate cysts from the Algarve Basin, southern 2 Portugal 3 4 Marisa E.N. Borges a,b, James B. Riding c,*, Paulo Fernandes a, Vasco Matos a, Zélia 5 Pereira b 6 7 a CIMA - Centro de Investigação Marinha e Ambiental, Universidade do Algarve, 8 Campus de Gambelas, 8005-139 Faro, Portugal 9 b LNEG-LGM, Rua da Amieira, 4465-965 S. Mamede Infesta, Portugal 10 c British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG12 11 5GG, UK 12 13 * Corresponding author. Tel.: +44(0)115 9363447 14 E-mail addresses: [email protected] (M.E.N. Borges), [email protected] (J.B. 15 Riding), [email protected] (P. Fernandes), [email protected] (V. Matos), 16 [email protected] (Z. Pereira). 17 18 ABSTRACT 19 The palynology of three Callovian (Middle Jurassic) limestone-marl successions from 20 the Algarve Basin in southern Portugal was studied. These localities are Baleeira 21 Harbour, Mareta Beach and Telheiro Quarry; they provide a composite succession, tied 1 22 to ammonite zones, through the Lower, Middle and Upper Callovian from the western 23 and eastern subbasins of the Algarve Basin. The three sections generally yielded 24 relatively abundant marine and continental palynofloras. Diversity is low to moderate 25 and the dinoflagellate cyst associations are dominated by Ctenidodinium spp., the 26 Ellipsoidictyum/Valensiella group, Gonyaulacysta jurassica subsp. adecta, 27 Korystocysta spp., Meiourogonyaulax spp., Pareodinia ceratophora, Sentusidinium 28 spp., Surculosphaeridium? vestitum and Systematophora spp. Some intra-Callovian 29 marker bioevents were recorded; these include the range bases of Ctenidodinium 30 ornatum, Gonyaulacysta eisenackii, Korystocysta pachyderma, Mendicodinium 31 groenlandicum, Rigaudella spp. -
Systematics, Endemism and Phylogeny of Indian Proplanulitins (Ammonoidea) from the Bathonian–Callovian of Kutch, Western India
Swiss J Palaeontol (2016) 135:23–56 DOI 10.1007/s13358-015-0101-2 Systematics, endemism and phylogeny of Indian proplanulitins (Ammonoidea) from the Bathonian–Callovian of Kutch, western India 1 1 Rakhi Dutta • Subhendu Bardhan Received: 25 February 2015 / Accepted: 28 August 2015 / Published online: 8 December 2015 Ó Akademie der Naturwissenschaften Schweiz (SCNAT) 2015 Abstract Spath (1931) described five genera namely Si- Bathonian of Kutch (Roy et al. 2007). Procerites was a vajiceras Spath, Obtusicostites Buckman, Hubertoceras European genus and perhaps gave rise to Proplanulites in Spath, Kinkeliniceras Buckman and Cutchisphinctes Spath the Boreal Europe. We here envisaged that Sivajiceratinae from the Upper Bathonian and entire Callovian of Kutch, and the European Proplanulitinae show evolutionary con- western India and included 33 species within them. He vergence of some characters since they evolved from a grouped these genera within the subfamily Proplanulitinae common ancestral stock. of the Boreal Province. But however the palaeobiogeo- graphic distributions of the Kutch forms suggest that they Keywords Sivajiceratinae Á New subfamily Á Kutch Á were restricted within the Indo-Madagascan Province. Middle Jurassic Á Palaeobiogeography Á Evolution Callomon (1993) expressed doubts about the phylogenetic affinity of Kutch genera and inferred that proplanulitins of Kutch were unrelated to Boreal Proplanulites and consti- Introduction tute an endemic lineage. In the present study, we made a thorough systematic revision of proplanulitin taxa of Kutch The Bathonian of Kutch, western India, witnessed sudden in the light of intraspecific variability and sexual dimor- migration of many ammonite genera from different pro- phism. Our study reveals that Spath’s (1931) work suffered vinces as soon as the Kutch Basin opened up (Roy et al. -
Geology of the Shepton Mallet Area (Somerset)
Geology of the Shepton Mallet area (Somerset) Integrated Geological Surveys (South) Internal Report IR/03/94 BRITISH GEOLOGICAL SURVEY INTERNAL REPORT IR/03/00 Geology of the Shepton Mallet area (Somerset) C R Bristow and D T Donovan Contributor H C Ivimey-Cook (Jurassic biostratigraphy) The National Grid and other Ordnance Survey data are used with the permission of the Controller of Her Majesty’s Stationery Office. Ordnance Survey licence number GD 272191/1999 Key words Somerset, Jurassic. Subject index Bibliographical reference BRISTOW, C R and DONOVAN, D T. 2003. Geology of the Shepton Mallet area (Somerset). British Geological Survey Internal Report, IR/03/00. 52pp. © NERC 2003 Keyworth, Nottingham British Geological Survey 2003 BRITISH GEOLOGICAL SURVEY The full range of Survey publications is available from the BGS Keyworth, Nottingham NG12 5GG Sales Desks at Nottingham and Edinburgh; see contact details 0115-936 3241 Fax 0115-936 3488 below or shop online at www.thebgs.co.uk e-mail: [email protected] The London Information Office maintains a reference collection www.bgs.ac.uk of BGS publications including maps for consultation. Shop online at: www.thebgs.co.uk The Survey publishes an annual catalogue of its maps and other publications; this catalogue is available from any of the BGS Sales Murchison House, West Mains Road, Edinburgh EH9 3LA Desks. 0131-667 1000 Fax 0131-668 2683 The British Geological Survey carries out the geological survey of e-mail: [email protected] Great Britain and Northern Ireland (the latter as an agency service for the government of Northern Ireland), and of the London Information Office at the Natural History Museum surrounding continental shelf, as well as its basic research (Earth Galleries), Exhibition Road, South Kensington, London projects. -
Callovian to Oxfordian Benthic Foraminifera from Ler Dome, Kutch Basin (Gujarat, India): Systematic, Ecostratigraphy and Palaeoenvironmental Reconstruction
Rivista Italiana di Paleontologia e Stratigrafia (Research in Paleontology and Stratigraphy) vol. 126(2): 315-362. July 2020 CALLOVIAN TO OXFORDIAN BENTHIC FORAMINIFERA FROM LER DOME, KUTCH BASIN (GUJARAT, INDIA): SYSTEMATIC, ECOSTRATIGRAPHY AND PALAEOENVIRONMENTAL RECONSTRUCTION SYED MD. WASIM1, MATIAS REOLID2*, ABU TALIB1 & SHABBER HABIB ALVI1 1Department of Geology, Aligarh Muslim University, 200 002 Aligarh, Uttar Pradesh, India. E-mail: [email protected] 2Department of Geology, University of Jaén, Campus Las Lagunillas sn 23071 Jaén, Spain. E-mail: [email protected] *Corresponding author. To cite this article: Wasim S. Md., Reolid M., Talib A. & Alvi S.H. (2020) - Callovian to Oxfordian benthic foraminifera from Ler Dome, Kutch Basin (Gujarat, India): Systematic, ecostratigraphy and palaeoenvironmental reconstruction. Riv. It. Paleontol. Strat., 126(2): 315-362. Keywords: Foraminifera; Systematics; Ecostratigraphy; Transgressive-regressive cycles; Kutch Basin. Abstract. Analysis of the foraminiferal assemblages of the Chari Formation (Middle-Upper Jurassic transi- tion) exposed at Ler Dome, Kutch Basin (India) allows one to interpret the incidence of different environmental parameters, especially the effect of sea-level changes in this group of microorganisms. The overall deposition of the Chari Formation took place in an open marine environment in the middle to outer shelf, having normal salinity and well-oxygenated bottom waters according to the lithofacies and the composition of the foraminiferal and macroin- vertebrate assemblages. Changes in the diversity, abundance of foraminifera, and proportion of specialist forms were associated mainly with the availability of labile organic matter on the sea floor. The changes in trophic resources were associated with fluctuations in the type of sedimentation, which ranges from carbonates to siltstones and sandstones. -
Ammonites from Bathonian and Callovian (Middle Jurassic)
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Universität München: Elektronischen Publikationen 253 Zitteliana 89 Ammonites from Bathonian and Callovian (Middle Jurassic) North of Damghan, Paläontologie Bayerische EasternGeoBio- Alborz, North Iran & Geobiologie Staatssammlung Center LMU München LMU München für Paläontologie und Geologie Kazem Seyed-Emami1* & Ahmad Raoufian2 München, 01.07.2017 1School of Mining Engineering, University College of Engineering, University of Tehran, Manuscript received P.O. Box 11365-4563, Tehran, Iran 2 26.09.2016; revision Daneshvar Center, Farhangian University, Neyshapour, Iran accepted 30.10.2016 *Corresponding author; E-mail: [email protected] ISSN 0373-9627 ISBN 978-3-946705-00-0 Zitteliana 89, 253–270. Abstract The following Middle Jurassic ammonite families (subfamilies) are described from the Dalichai Formation north of Damghan (eastern Alborz), some of them for the first time: Phylloceratidae, Lytoceratidae, Oppeliidae (Hecticoceratinae), Stephanoceratidae (Cadomitinae), Tulitidae and Reineckeiidae. The fauna is typically Northwest-Tethyan and closely related to Central Europe (Subboreal – Submediterra- nean Provinces). Key words: Ammonites, Dalichai Formation, Middle Jurassic, Alborz, Iran Zusammenfassung Aus der Dalichai Formation nördlich von Damghan (Ostalborz) werden einige mitteljurassische Ammoniten, teils zum ersten Mal, beschrieben. Folgende Familien und Unterfamilien sind vertreten: Phylloceratidae, Lytoceratidae, Oppeliidae (Hecticoceratinae), Steph- anoceratidae (Cadomitinae), Tulitidae und Reineckeiidae. Die Fauna ist typisch für die Nordwest-Tethys und zeigt enge Beziehungen zu Zentraleuropa (Subboreale und Submediterrane Faunenprovinz). Schlüsselwörter: Ammoniten, Dalichai Formation, Mittlerer Jura, Alborz, Iran Introduction the frame of a MSc. thesis. For the present study, a new section nearby was chosen and collections The present study is a continuation of a larger re- were made by A. -
Callovian(Middle Jurassic)Ammonite Faunas of the Northwest Iberian Ranges: B Iostratigraphy and Palaeobiogeography
Batizonjan - Callovian(Middle Jurassic)ammonite faunas of the Northwest Iberian Ranges: b iostratigraphy and palaeobiogeography J. THIERR’? and 5. WILDE** 0 157 «Géodynamique sédimentaire et Evolution géobiologique» * URA ~ii7NRSn eL Centre des Sejences de la Terre, Université de Boargogne, 6 Rd Gabrial 21100 DIJON (France) ** Jns¿ñrnJí¿r Gealogie, Ruhr-Universitñ¿ D-4630 BOCHUM, (RE4) XBSTRACT Thc Bathonian-Callovian carbonated sedimenis, sometimes sandy or silty and ctayish, of the Iberian ptatform in Ihe Sierras de la Demanda, Cameros ami Moncayo near Burgos, Logroño, Soria ami Zaragoza (North- west Iberian Ranges) yeld significant ammonite faunas for a precise bios- tratigraphic approach; these also allow sorne biogeographic remarks about Ihis region situated in platform environrnents almost off on the North Tethyan margin. During the Bathonian (Montenegro, Soria, Olvega and Ricla forma- tions) the faunas are dominated by the Perisphinctidae (Procerites, Siemi- radkia, Wagnericeraá; h’omeop/anulñes. Ch~ffatia —70 %)4 the other taxa are sorne Oppelidae (Oxycerites, Qecotraustes Prohecticoceras —20 %). Parkinso- niidae (Gonolkites bipistrenoceras —5 %) and Tulitidae íBullatimorphites —5 %). The various recognized species allow to conclude that the Lower Bathonian (Zigzag zone; Convergens and Yeovilensis subzones) is repre- sented as weIl as the Middle Bathonian (Progracilis and Subeontractus zones; Subeontractus and Morrisi subzones) and the Upper Bathonian (Retrocostaturn zone and subzone). It must be noted that Morphoceratidae of Lowermost Baihonian and Clydoniceratidae of Upperrnost Bathonian are missing. In Callovian, (Montenegro, Pozalmuro and Ricla formations) only Ihe lower pad of Ihis stage is dcli in ammonites. The Macroceplialus and Gracilis zones are weII distinguished witb prevalent Macrocephalitidae (Macrocephalites —45 %) and Perisphinctidae (Choifatia, Homeoplanulites, Indosphinctes, Grossouvria —40 %). -
Environments and Faunal Patterns in the Kachchh Rift Basin
Rivista Italiana di Paleontologia e Stratigrafia volunre I i 0 no. I pp.181-190 April 2004 ENVIRONMENTS AND FAUNAL PATTERNS IN THE KACHCHH RIFT BASIN. \TESTERN INDIA, DURING THE JURASSIC FRANZ THEODOR FURSICH', JOHN H. CALLOMON" DHIRENDRA K. PANDEY.E{ ANAND K. TAITLY* Recit,ed September 19, 2002: accepted July 13,2003 Key-zoords: Jurassic, taphonomy, palaeoecology, cycles, Kach- dominata dai bivalvi, seguiti da brachiopodi, gasteropodi, coralli, ser- chh, India. pulidi e spugne. Lanalisi di 370 campioni statistici ed oltre 27000 esem- plari h;r prodotto più di a0 associazioni e rrggruppamenti bentonici. Abstract. Marine Jurassic sediments (Bajocian-Tithonian) of the Essi mostrano una relazione con molti parametri ambientali, due dei Kachchh Basin were deposited in a ramp setting. Except during the quali, salinità e clima, vengono brevemente discussi. Viene delineata la Middle and Late Bathonian, when a carbonate reginre became estab- distribuzione areale delle facies e dei biota per due porzioni temporali, lished, the fill of the basin consists predominantly of siliciclastics. The rispettivamente il Bathoniano ed il Calloviano-Oxfordiano. sediments represent environnrents that range from coastal plains (riv- ers and associated flood plains with caliche nodules), deltas, brackish water lagoons, nearshore sand and iron-oolite bars of the inner rlmp, generally situated above fair-weather wave-base, to the middle ramp in- Introduction fluenced by stornr-waves and by storm-generated currents, and finally to the outer ramp which is characterised by lor. energy, fine-grained The rift basin of Kachchh originated at the west- sediments. Changes in relative sea level produced a cyclic sedimenta- ern margin of the Indian Plate in the Triassic (e.g. -
Responses of Benthic Foraminifera to Environmental Variability a Case
Marine Micropaleontology 151 (2019) 101749 Contents lists available at ScienceDirect Marine Micropaleontology journal homepage: www.elsevier.com/locate/marmicro Responses of benthic foraminifera to environmental variability: A case from T the Middle Jurassic of the Kachchh Basin (Western India) ⁎ Sreepat Jaina, , Ahmed Awad Abdelhadyb, Mohamad Alhusseinc a Department of Geology, School of Applied Natural Science, Adama Science and Technology University, 1888 Adama, Oromia, Ethiopia b Geology Department, Faculty of Science, Minia University, 61519 Minia, Egypt c Department of Geology, Aleppo University, Aleppo, Syria ARTICLE INFO ABSTRACT Keywords: At the western margin of the Indian plate, the Jurassic sedimentary succession of the Kachchh Basin provides Middle Jurassic well–developed exposures for fauna-based studies. Based on a quantitative analyses of 67 samples spanning Kachchh Middle Bathonian–Late Callovian interval, the paleoenvironment of the Jumara section (the depocenter of the Sea level Kachchh basin), is inferred. Four benthic foraminiferal assemblages are recognized by both Clustering and NMDS Clustering ordination methods. These assemblages vary in biotic traits such as life–habit and diversity as well as in abiotic NMDS ordination traits such as sediment type, nutrient availability, and oxygen level. The Bathonian Spirillina polygyrata assem- blage that dominates an outer neritic oligotrophic setting, has a preference for calcareous substrates. In the earliest Callovian, the Epistomina mosquensis assemblage replaced the latter, as oxic conditions decreased and terrigenous influx increased. Two successive and less diverse assemblages had a preference for non–calcareous substrates and dominated the mid-Early–Late Callovian landscape. These are the oxic Lenticulina subalata as- semblage (inner to middle neritic oligotrophic setting) in the mid–Early to mid–Middle Callovian and the dysoxic Reophax metensis assemblage (mesotrophic to eutrophic middle neritic setting) in the late–Middle to Late Callovian. -
Upper Jurassic Mollusks from Eastern Oregon and Western Idaho
Upper Jurassic Mollusks from Eastern Oregon and Western Idaho GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-D Upper Jurassic Mollusks from Eastern Oregon and Western Idaho By RALPH W. IMLAY CONTRIBUTIONS TO PALEONTOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-D Faunal evidence for the presence of Upper Jurassic sedimentary rocks in eastern Oregon and westernmost Idaho UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Abstract.__________________________________________ Dl Ages and correlations Continued Introduction.______________________________________ 1 Trowbridge Formation of Lupher, 1941, in east- Biologic analysis..._________________________________ 2 central Oregon.__________---_-_-__-_-____---_ D9 Stratigraphic summary._____________________________ 2 Lonesome Formation of Lupher, 1941, in east-central Northeastern Oregon and adjoining Idaho. ________ 2 Oregon..________________-_--_____--_--_---__ 9 Mineral area, western Idaho.____________________ 2 Comparisons with other faunas.______________________ 10 East-central Oregon_____________________________ 4 Alaska and western British Columbia-____________ 10 Conditions of deposition.____________________________ 6 Calif ornia. ... _ __-_________--____-___-__---___-_ 10 Ages and correlations______________________________ 6 Unnamed beds in northeastern Oregon and adjoining Western interior of North America._______________ 10 Idaho_______________________________________ Geographic distribution________-_-_____---_---_-.__ 11 Unnamed beds near Mineral, Idaho.______________ Systematic descriptions..._--_--__-__________________ 13 Snowshoe Formation of Lupher, 1941, in east-central Literature cited_____-__-_____---------_-_--_--__-___ 17 Oregon._____________________________________ Index_.______________--____---------_-__---_-_-___ 21 ILLUSTRATIONS [Plates 1-4 follow index] PLATE 1. -
Depositional Environments, Facies and Diagenesis of The
Annales Societatis Geologorum Poloniae (2016), vol. 86: 165–183. doi: http://dx.doi.org/10.14241/asgp.2016.005 DEPOSITIONAL ENVIRONMENTS, FACIES AND DIAGENESIS OF THE UPPER JURASSIC–LOWER CRETACEOUS CARBONATE DEPOSITS OF THE BUILA-VÂNTURARIÞA MASSIF, SOUTHERN CARPATHIANS (ROMANIA) George PLEª, Ioan I. BUCUR & Emanoil SÃSÃRAN Department of Geology, Babeº-Bolyai University, M. Kogãlniceanu 1, 400084 Cluj-Napoca, Romania; e-mails: [email protected]; [email protected]; [email protected] Pleº, G., Bucur, I. I. & Sãsãran, E., 2016. Depositional environments, facies and diagenesis of the Upper Jurassic–Lower Cretaceous carbonate deposits of the Buila-Vânturariþa Massif, Southern Carpathians (Romania). Annales Societatis Geologorum Poloniae, 86: 165–183. Abstract: The Buila-Vânturariþa Massif consists of massive Upper Jurassic reef limestones (Kimmeridgian– Tithonian) and Lower Cretaceous (Berriasian–Valanginian, and Barremian–?Lower Aptian) deposits. Besides corals and stromatoporoids, a wide range of micro-encrusters and microbialites has contributed to their deve- lopment. In this study, the authors describe briefly and interpret the main facies associations and present the microfossil assemblages that are important for age determination. The distribution of facies associations, corro- borated with the micropalaeontological content and early diagenetic features, indicate different depositional environments. The carbonate successions show the evolution of the Late Jurassic–Early Cretaceous depositional environments from slope and reef-front to internal-platform sedimentary settings, including peritidal environ- ments in the lowermost Cretaceous. Early diagenesis, represented by synsedimentary cementation in the form of micritization (including cement crusts in the reef microframework), followed by dissolution, cementation and dolomitization in a meteoric regime, and void-filling late cementation during the burial stage.