Ancient Microbial Gas in the Upper Cretaceous Milk River Formation, Alberta and SaskatchewanA Large Continuous Accumulation in Fine-grained Rocks

2012 ◽  
Author(s):  
Neil S. Fishman ◽  
Jennie L. Ridgley ◽  
Debra K. Higley ◽  
Michele L. W. Tuttle ◽  
Donald L. Hall
Keyword(s):  
Upper Cretaceous ◽  
Fine Grained ◽  
Milk River Formation ◽  
Continuous Accumulation

scholarly journals High-frequency sea-level changes recorded in deep-water carbonates of the Upper Cretaceous Dol Formation (island of Brač, Croatia)

2010 ◽  
Vol 61 (1) ◽  
pp. 29-38
Author(s):  
Damir Bucković ◽  
Maja Martinuš ◽  
Duje Kukoč ◽  
Blanka Tešović ◽  
Ivan Gušić
Keyword(s):  
Sea Level ◽  
Deep Water ◽  
High Frequency ◽  
Upper Cretaceous ◽  
Distal Part ◽  
Preferential Orientation ◽  
Sea Level Changes ◽  
Carbonate Production ◽  
Fine Grained ◽  
Platform Margin

High-frequency sea-level changes recorded in deep-water carbonates of the Upper Cretaceous Dol Formation (island of Brač, Croatia)The upper part of the Middle Coniacian/Santonian-Middle Campanian deep-water Dol Formation of the island of Brač is composed of countless fine-grained allodapic intercalations deposited in an intraplatform trough. Within the studied section 13 beds can be distinguished, each defined by its lower part built up of dark grey limestone with abundance of branched, horizontally to subhorizontally oriented burrows, and the upper part, in which the light grey to white limestone contains larger burrows, rarely branched, showing no preferential orientation. The lower, dark grey, intensively bioturbated levels are interpreted as intervals formed during high-frequency sea-level highstands, while the upper, light grey-to-white levels are interpreted as intervals formed during the high-frequency sea-level lowstands. Cyclic alternation of these two intervals within the fine-grained allodapic beds is interpreted as the interaction between the amount of carbonate production on the platform margin and the periodicity and intensity of shedding and deposition in the distal part of toe-of-slope environment, which is governed by Milankovitch-band high frequency sea-level changes.

scholarly journals Exsolution Lamellae in Orthopyroxene of Lherzolite from the Pauza Ultramafic Rocks, Ne Iraq: Evidence of Deep Mantle Signature in the Zagros Suture Zone

2013 ◽  
Vol 2 (9) ◽  
pp. 102-115
Author(s):  
Yousif Osman Mohammad ◽  
Nabaz Rashid Hama Aziz
Keyword(s):  
High Pressure ◽  
Upper Cretaceous ◽  
Suture Zone ◽  
Ultramafic Rocks ◽  
Chromian Spinel ◽  
Spinel Peridotite ◽  
Incongruent Melting ◽  
Fine Grained ◽  
Ultra High Pressure ◽  
Deep Mantle

The Pauza ultramafic body is part of Upper Cretaceous Ophiolitic massifs of the Zagros Suture Zone, NE Iraq. The present study reveals evidence of Ultra-high pressure (UHP), and deep mantle signature of these peridotites in the Zagros Suture Zone throughout the observation of backscattered images and micro analyses which have been performed on orthopyroxen crystals in lherzolite of Pauza ultramafic rocks.Theorthopyroxen shows abundant exsolution lamellae of coarse unevenly distributed clinopyroxene coupled with the submicron uniformly distributed needles of Cr-spinel. The observed clusters of Opx–Cpx–Spl represent the decompression products of pyrope-rich garnet produced as a result of the transition from ultra-high pressure garnet peridotite to low-pressure spinel peridotite (LP). Neoblastic olivine (Fo92 – 93) with abundant multi-form Cr- spinel inclusions occurs as a fine-grained aggregate around orthopyroxene, whereas coarse olivine (Fo90-91) free from chromian-spinel is found in matrix. The similarity of the Cr-spinel lamellae orientations in both olivine and orthopyroxene, moreover, the enrichments of both Cr and Fe3+ in the Cr-spinel inclusions in neoblastic olivine relative to Cr-spinel lamellae in orthopyroxene, suggest that spinel inclusions in olivine have been derived from former Cr-spinel lamellae in orthopyroxene. Neoblastic olivine is formed by reaction of silica-poor ascending melt and orthopyroxene. It is inferred that the olivines with multi-form spinel inclusions has been formed by incongruent melting of pre-existing spinel lamellae-rich orthopyroxene.

scholarly journals The Middle Cenomanian basal series of Planinica, Western Serbia

2002 ◽  
pp. 13-43 ◽  
Author(s):  
Dragoman Rabrenovic ◽  
Nebojsa Vasic ◽  
Jovanka Mitrovic-Petrovic ◽  
Vladan Radulovic ◽  
Barbara Radulovic ◽  
...  
Keyword(s):  
New Taxa ◽  
Upper Cretaceous ◽  
Sedimentary Rocks ◽  
Structural Features ◽  
Upper Miocene ◽  
Fine Grained ◽  
The Village ◽  
Marly Limestone

Sedimentary rocks of the Upper Cretaceous basal series found at the village of Planinica, Western Serbia, are composed of thick coarse clastics and beds and intercalations of medium- to fine-grained clastics. The series lies transgressively over Jurassic serpentinite and peridotite, and under Upper Miocene marlstone and marly limestone. Sedimentary, petrographic, paleontological, and biostratigraphic characteristics of the basal series are described and its lithological members and their structural features are identified. From medium-grained sandy matrix in thick coarse clastics, two ammonite taxa, four brachiopod taxa (including the new taxa Orbirhynchia oweni and "Terebratula" n. gen. et sp.), and eleven echinoid taxa are described. The brachiopod species Kingena concinna Owen is used in dating the basal series as Middle Cenomanian, whereas limestone fragments in coarse clastics correspond to the Late Albian and Early Cenomanian.

The mineralogy and petrology of the Pahnavar Fe skarn, In the Eastern Azarbaijan, NW Iran

2012 ◽  
Vol 4 (4) ◽  
Author(s):  
Mir Mokhtari
Keyword(s):  
Heat Flow ◽  
Aqueous Phase ◽  
Carbonate Rocks ◽  
Mineral Assemblage ◽  
Upper Cretaceous ◽  
Nw Iran ◽  
Fine Grained ◽  
Enclosing Rocks

AbstractThe Pahnavar calcic Fe-bearing skarn zone is located in the Eastern Azarbaijan (NW Iran). This skarn zone occurs along the contact between Upper Cretaceous impure carbonates and an Oligocene granodioritic batholith. The skarnification process can be categorized into two discrete stages: prograde and retrograde. The prograde stage began immediately after the initial emplacement of the granodioritic magma into the enclosing impure carbonate rocks. The effect of heat flow from the batholith caused the enclosing rocks to become isochemically marmorized in the pure limestone layers and bimetasomatized (skarnoids) in the impure clay-rich carbonates. Segregation and evolution of an aqueous phase from the magma that infiltrated to the marbles and skarnoids through fractures and micro-fractures took place during the emplacement of magma. The influx of Fe, Si and Mg from the granodiorite to the skarnoids and marbles led to the crystallization of anhydrous calc-silicates (garnet and pyroxene).The retrograde stage can be divided, in turn, into two distinct sub-stages. During earliest sub-stage, the previously formed skarn assemblages were affected by intense hydro-fracturing; in addition, Cu, Pb, Zn, along with H2S and CO2 were added. Consequently, hydrous calc-silicates (epidote and tremolite-actinolite), sulfides (pyrite, chalcopyrite, galena and sphalerite), oxides (magnetite and hematite) and carbonates (calcite) deposited the anhydrous calc-silicates. The late-retrograde sub-stage was due the incursion of colder oxidizing fluids into the skarn system, causing the alteration of the previously formed calc-silicate assemblages and the development of fine-grained aggregates of chlorite, illite, kaolinite, hematite and calcite.The lack of wollastonite in the mineral assemblage, along with the garnet-clinopyroxene paragenesis, suggests that the prograde stage formed under temperature and fO2 conditions of 430–550°C and 10−26–10−23, respectively.

scholarly journals The Jurassic–Cretaceous lithostratigraphy of Kilen, Kronprins Christian Land, eastern North Greenland

2018 ◽  
Vol 66 ◽  
pp. 61-112 ◽  
Author(s):  
Jussi Hovikoski ◽  
Gunver K. Pedersen ◽  
Peter Alsen ◽  
Kristian Svennevig ◽  
Henrik Nøhr Hansen ◽  
...  
Keyword(s):  
Lower Cretaceous ◽  
Upper Cretaceous ◽  
Field Work ◽  
Shallow Marine ◽  
Fine Grained ◽  
North Greenland ◽  
Sandy Mudstone ◽  
Cretaceous Sediment

Kilen, Kronprins Christian Land, contains the thickest and stratigraphically most complete Jurassic and Cretaceous sediment succession in North Greenland. This study revises and formalises the lithostratigraphic framework of these deposits. The work is based on recent extensive stratigraphic field work supplemented by photogeological mapping and biostratigraphic studies, and builds on the earlier stratigraphic work conducted mainly in the 1980s and 1990s. According to the new stratigraphic scheme, the more than 500 m thick Jurassic succession is divided into four formations. The poorly dated Gletscherport Formation comprises lagoonal heterolithic sandstones. The Mågensfjeld and Birkelund Fjeld Formations consist of shallow marine fine-grained sandstones of Bajocian–Bathonian and Kimmeridgian age, respectively. The Kuglelejet Formation comprises mainly shallow marine sandy mudstone and sandstone of Volgian age and includes the mudstone-dominated Splitbæk Member. The Lower Cretaceous interval is estimated to be more than 1500 m thick and is divided into three formations. The Dromledome Formation comprises deep shelf to offshore transition, black mudstones of late Ryazanian to Hauterivian age. It is erosively overlain by unfossiliferous, fluvial and estuarine sandstones of the Lichenryg Formation. The overlying, late Aptian to middle Cenomanian Galadriel Fjeld Formation comprises six members, of which the Tågekyst and Kangoq Ryg Members occur in the Gåseslette area, whereas the Pil, Valmue, Stenbræk and Hondal Members occur in the Kilen Fjelde area. The Galadriel Fjeld Formation is characterised by interbedded mudstones and sandstones from offshore–shoreface environments. The 650 m thick Upper Cretaceous succession is assigned to the Sølverbæk Formation, which is undivided in the Gåseslette area and divided into the Skalbæk and Scaphitesnæse Members in the Kilen Fjelde area. The Sølverbæk Formation is dominated by marine mudstones and sandstonemudstone heteroliths of late Cenomanian to Santonian age. The new lithostratigraphic framework and significant biostratigraphic advances allow a closer correlation of the Mesozoic units between North Greenland and other Arctic basins.

scholarly journals Upper Cretaceous rhyolitic ashes in the Utes Derevyannykh Gor area (Novaya Sibir Island, the New Siberian Islands)

2019 ◽  
Vol 20 (1) ◽  
pp. 37-47
Author(s):  
V. V. Kostyleva ◽  
E. V. Shchepetova ◽  
A. E. Kotelnikov
Keyword(s):  
Upper Cretaceous ◽  
Microprobe Analysis ◽  
Clay Fraction ◽  
Field Work ◽  
Pyroclastic Material ◽  
New Siberian Islands ◽  
High Potassium ◽  
X Ray ◽  
Fine Grained ◽  
Scanning Electron

The article is concerned with the first finds of rhyolite ashes in Upper Cretaceous sediments of Novaya Sibir Island. In the course of the field work in the area of cape Utes Derevyannykh Gor in 2016, four layers of unlithified fine-grained ashes were found in the Turonian-Coniacian coal-bearing Derevyannye Gory Formation. The article presents the results of petrographic, X-ray diffractometric and microprobe analysis of pyroclastics from ash layers. A typification of volcanogenic-terrigenous deposits is proposed. Thin section of the samples were investigated on a polarizing microscope. X-ray phase analysis of the clay fraction was carried out using a DRON-3 diffractometer. X-ray microanalysis of vitroclasts were carried out on a scanning electron microscope “Jeol JSM-6480LV” with the microprobe analyzer “Oxford Instruments INCA-Energy 350”. It was established that Derevyannye Gory Formation is composed of rhyolitic tuffites, among which fine-grained crystal-vitroclastic and vitroclastic ashes of low and normal alkaline high-potassium rhyolites with thickness up to 2.5 m. Low pyroclastics sediments are not widespread. New data on the structure and composition of the Derevyannye Gory Formation confirm the hypothesis of previous researchers, that sedimentation in the Late Cretaceous in the area of Novaya Sibir Island was accompanied by explosive acidic volcanism. The main purpose of the article is to discuss the sources of pyroclastic material for the territory of the New Siberian Islands in the Turonian-Coniacian age. The conclusion is made about the territorial proximity of the paleovolcanic eruption center to the area of sedimentation. It is assumed that the paleovolcanic centers were located within the present territory of Kotelny, Zemlya Bunge, Faddeevsky islands and, probably, were inherited from the Early Albian stage.

Functional morphology and taxonomic significance of a novel cuticular Structure in Cretaceous Raninid crabs (Decapoda: Brachyura: Raninidae)

2002 ◽  
Vol 76 (3) ◽  
pp. 472-485 ◽  
Author(s):  
A. E. Haj ◽  
Rodney M. Feldmann
Keyword(s):  
Cross Section ◽  
Upper Cretaceous ◽  
Anterior Margin ◽  
Frictional Resistance ◽  
Structure And Function ◽  
Coarse Grained ◽  
Fort Worth ◽  
Fine Grained ◽  
Cuticular Structure ◽  
And Function

Fossil raninid crabs, Cretacoranina punctata (Rathbun, 1935), from the Pawpaw Formation (Upper Cretaceous) of Fort Worth, Texas, exhibit an unusual cuticular morphology. Comparison of the cuticle of extant Raninoides louisianensis to that of C. punctata reveals general similarities in endocuticular, exocuticular, and epicuticular ultrastructure; however, their gross morphology is strikingly different. The surface of the carapace of C. punctata appears pebbled, much like the surface of a basketball, with closely packed, hexagonal caps. In cross-section, these caps are the upper portion of fungiform structures within convoluted exocuticle. Along the anterior margin, anterolateral margins, and pterygostomial region of the carapace of C. punctata each cap dips slightly posteriorly, creating a series of tiny terraces. In contrast to terrace lines, questa lines, spines, and nodes that provide frictional resistance in interactions with coarse-grained sediments, the fine relief and contouring of the pebbled surface of the carapace of C. punctata provides frictional resistance in interactions with fine-grained sediments. Cretacoranina dichrous, C. trechmanni, C. testacea, and C. schloenbachi, as well as Eucorystes carteri were all found to possess variations of the exocuticular structures seen on C. punctata. This pebbled surface has not been recognized in any other decapod taxon, nor has its structure and function been described previously.

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