• The Korean Journal of Petroleum Geology
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• v.12 no.1
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• pp.1-8
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• 2006

Jiaolai Basin is the Cretaceous continental sedimentary basin developed in Shandong Province of China. It is interpreted as a pull-apart basin which is filled with fluvio-lacustrine sediments and volcanic rocks. The sedimentary strata are divided into three formations: Laiyang Formation, Qingshan Formation and Wangshi Formation in ascending order. Laiyang Formation of the early Cretaceous consists of conglomerate, sandstone and shale, which are grey, black or red in color, respectively. Qingshan Formation of early Cretaceous includes various kinds of volcanic rocks. Late Cretaceous Wangshi Formation consists of red conglomerate, sandstone and shale. Various types of oil shows are observed on many outcrops in the basin such as asphalt filing fissures, oil smelling, rocks wetted with oil. However, commercial oil discovery was not made. Laiyang Formation is the richest in terms of organic matter contents. Some grey or black shales of Laiyang Formation contain more than 1% of organic matter. Kerogens of some layers mainly consist of amorphous organic matter or pollen. Thermal maturity of the organic matter reached main oil generation zone and hydrocarbon genetic potential is fairly good. According to such geochemical data, some layers of Laiyang Formation can act as hydrocarbon source rocks.

• Economic and Environmental Geology
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• v.40 no.4
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• pp.473-490
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• 2007

Strata of the Kachi-1 well, Kunsan Basin, offshore western Korea, were analyzed by using integrated stratigraphy approach. As a result, five distinct unconformity-bounded units are recognized in the well: Triassic, Late Jurassic-Early Cretaceous, Early Cretaceous, Late Cretaceous, and Middle Miocene units. Each unit represents a tectono-stratigraphic unit that provides time-sliced information on basin-forming tectonics, sedimentation, and basin-modifying tectonics of the Kunsan Basin. In the late Late Jurassic, development of second- or third-order wrench faults along the Tan-Lu fault system probably initiated a series of small-scale strike-slip extensional basins. Continued sinistral movement of these wrench faults until the Late Cretaceous caused a mega-shear in the basin, forming a large-scale pull-apart basin. However, in the Early Tertiary, the Indian Plate began to collide with the Eurasian Plate, forming a mega-suture zone. This orogenic event, namely the Himalayan Orogeny, continued by late Eocene and was probably responsible for initiation of right-lateral motion of the Tan-Lu fault system. The right-lateral strike-slip movement of the Tan-Lu fault caused the tectonic inversion of the Kunsan Basin. Thus, the late Eocene to Oligocene was the main period of severe tectonic modification of the basin. After the Oligocene, the Kunsan Basin has maintained thermal subsidence up to the present with short periods of marine transgressions extending into the land part of the present basin.

• The Korean Journal of Petroleum Geology
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• v.7 no.1_2 s.8
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• pp.28-34
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• 1999

The Cretaceous Poongam sedimentary Basin in Kangwon-do, Korea consists alluvial deposits of conglomerates, sandstones, mudstones or siltstones, and volcaniclastics. The Poongam Basin was formed as a fault margin sag or a transpressional basin developed along a strike-slip fault zone, and received huge amount of clastic sediments from the adjacent fault-scaip. It formed an aggrading alluvial fan system and a volcaniclast-supplied marginal lake environment, while tectonic activity and volcanism attenuated toward the end of basin formation. Following the Folk's classification, the sandstones of the Poongam Basin are identified as lithic wackes or feldspathic wackes. The areal and sequential variation of the mineral composition in the sandstones is not distinct. The results of K-Ar age dating from the intruding andesites, volcaniclastics and volcanic fragments in sedimentary rocks show a range of 70 Ma to 84 Ma. It suggests that volcarism occurred sequentially within a relatively short period as the pre-, syn-, and post-depositional events. It was the short period in the late Cretaceous that the basin had evolved i.e., the basin formation, the sediment input and fill, and the , intrusion and extrusion of volcanic rocks occurred. The Poongam sedimentary sequence is a typical tectonic-controlled coarse sedimentary facies which is texturally immature.

• The Journal of the Petrological Society of Korea
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• v.21 no.2
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• pp.217-233
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• 2012

Major elements abundances of Cretaceous to Tertiary volcanic rocks in Kyongsang basin are similar with Southern Volcanic Zone (SVZ) in Andes. Sr, K, Rb, $Ba{\pm}Th$ abundances, which have low ionic charge, are selectively fertile, on the other hand Ta, Nb, Ce, P, Zr, Hf, Sm, Ti, Y, Yb, Sc, Cr abundances are low. K, Sr, Th show characteristic spikes and Nb show remarkable trough on trace elements spider diagram. Trace elements abundances are higher than that of Andes which is supposed to mantle sources of Kyongsang basin volcanic rocks are produced lower degree of partial melting than SVZ in Andes.

• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.273-286
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• 2006

The Kyongsang Basin is the most representative Cretaceous basin in the Korean Peninsula where extensive crustal deformation and non-marine sedimentation took place in the early Cretaceous period. The lithology of the basement of the basin and adjacent areas is comprised of mainly Precambrian gneiss complex and Mesozoic granite intrusions. We have carried out magnetotelluric (MT) surveys to investigate the deep geoelectric structure around the Kyongsang Basin. The MT data were collected in the frequency range from 0.00042 to 320 Hz at 24 sites along a profile across the northern part of Kyongsang Basin. The results of MT inversion show that the thickness of sediments is estimated about 3 km to 9 km and the depth to base of granite intrusion is about 20 km. A remarkable discovery in this study is the highly conductive layer beneath the basin, having the resistivity of 1 ohm-m to 30 ohm-m and the thickness of about 3 km to 4 km or more. Although we are not able to reveal the nature of this layer, the result of this study could provide some basic information with respect to the formation process and deposit environment of the proto-Kyongsang Basin.

• Economic and Environmental Geology
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• v.47 no.4
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• pp.381-393
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• 2014

Seismic reflection data are integrated with fieldwork data in order to understand startigraphy, structural geology and hydrocarbon potentials of Cretaceous strata in the Mesopotamian basin, Northeastern Iraq. Cretaceous strata in the basin divided into the Qamchuqa, Kometan, Bekhme and Shiranish formations, which are composed of carbonates deposited in shallow marine environment. The geological structures in these formations are mainly recognized as thrusts, detachment folds, fault propagation folds and fault bend folds. As well, NW-SE trending fractures are regularly developed, and are horizontal or perpendicular to the structures. The distribution and frequency of fractures are related to the development of the thrusts. In terms of hydrocarbon potentials, Cretaceous strata in the basin have limited capacities for source rocks and seal rocks due to the lack of organic carbon content and the well-developed fractures, respectively. Although these carbonates have limited primary porosity, however, development of the secondary porosity derived from the fractures contributes to enhance the reservoir quality. Most important factor for the reservoir quality of Cretaceous strata seems to be the frequency and connectivity of fractures relative to locations of folds and faults. The results delineated in this study will use as reference for recognizing stratigraphy and structures of Cretaceous strata and will provide useful information on hydrocarbon potentials of Cretaceous strata in the Mesopotamian basin, NE Iraq.

• Journal of the Korean earth science society
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• v.39 no.6
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• pp.545-554
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• 2018

The Cretaceous Eumsung (Eumseong) Basin is a pull-apart basin, formed along a series of the Gongju strike-slip faults trending NE-SW. The Nongdari-Meer forest of the Gugokri area in the southwestern part of the basin is comprised of thick purple mudstone, intercalating conglomerate, pebbly sandstone, and green mudstone beds. The succession mainly consists of seven sedimentary facies: stratified conglomerate (C2), conglomerate encased in siltstone (CE), stratified pebbly sandstone encased in siltstone (PSE2), purple sandy siltstone (Zp), green sandy siltstone (Zg), purple mudstone (Mp), and green mudstone (Mg). Sedimentary environment is mainly indicative of alluvial-plain setting in an alluvial-to-lacustrine sedimentary system, developed in the southwestern part of the basin. Geological survey was fulfilled in succession of the Gugokri sedimentary system using 1:5000 topographic map, which resulted in a geological route map. This study newly suggested that there be fluvial systems showing ENE and NNE trends in the study area, based on data of palaeocurrent direction and sedimentary characteristics in new outcrops of the forest. The study also revised the precedent sedimentation model of the Gugokri system.

• Economic and Environmental Geology
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• v.29 no.3
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• pp.247-256
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• 1996

Mineral commodities of metallic ore deposits related to Cretaceous granitoids in the Taebaegsan basin are distinguishable by rock types, diffferenciation index (D.I.) and chemical compositions. Deposits of Fe-Cu are related to granodiorite-quartz monzonite, those of Pb-Zn and W-Mo to granite-granodiorite and granite respectively. The ranges of D.I. of the granitoids are 39~71 for Fe-Cu deposits, 68~81 for Pb-Zn deposits, 78~89 for W-Mo deposits and 91~94 for Mn deposits. Major oxides of $K_2O$, CaO, MgO, FeO and $TiO_2$ and some trace elements and Rb/K, Sr/Ca and Cu/Fe also show distinguishable differences among the Cretaceous granitoids related to various mineral commodities of the ore depsits.

• The Korean Journal of Petroleum Geology
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• v.4 no.1_2 s.5
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• pp.27-39
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• 1996

In the Cretaceous, the Gulf Coast Basin evolved as a marginal sag basin. Thick clastic and carbonate sequences cover the disturbed and diapirically deformed salt layer. In the Cretaceous the salinities of the Gulf Coast Basin probably matched the Holocene Persian Gulf, as is evidenced by the widespread development of supratidal anhydrite. The major Lower Cretaceous reservoir formations are the Cotton Valley, Hosston, Travis Peak siliciclastics, and Sligo, Trinity (Pine Island, Pearsall, Glen Rose), Edwards, Georgetown/Buda carbonates. Source rocks are down-dip offshore marine shales and marls, and seals are either up-dip shales, dense limestones, or evaporites. During this period, the entire Gulf Basin was a shallow sea which to the end of Cretaceous had been rimmed to the southwest by shallow marine carbonates while fine-grained terrigengus clastics were deposited on the northern and western margins of the basin. The main Upper Cretaceous reservoir groups of the Gulf Coast, which were deposited in the period of a major sea level .rise with the resulting deep water conditions, are Woodbinefruscaloosa sands, Austin chalk and carbonates, Taylor and Navarro sandstones. Source rocks are down-dip offshore shales and seals are up-dip shales. Major trap types of the Lower and Upper Cretaceous include salt-related anticlines from low relief pillows to complex salt diapirs. Growth fault structures with rollover anticlines on downthrown fault blocks are significant Gulf Coast traps. Permeability barriers, up-dip pinch-out sand bodies, and unconformity truncations also play a key role in oil exploration from the Cretaceous Gulf Coast reservoirs. The sedimentary sequences of the major Cretaceous reseuoir rocks are a good match to the regressional phases on the global sea level cuwe, suggesting that the Cretaceous Gulf Coast sedimentary stratigraphy relatively well reflects a response to eustatic sea level change throughout its history. Thus, of the three main factors controlling sedimentation (tectonic subsidence, sediment input, and eustatic sea level change) in the Gulf Coast Basin, sea-level ranks first in the period.

• 한국석유지질학회:학술대회논문집
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• spring
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• pp.48-55
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• 1998

The Pohang Basin is located in Pohang City and adjacent coastal areas in the southeastern Korea. It has a sequence of 900 meters of Neogene marine sediments (Yeonil Group) while offshore basins in the East Sea, e.g., the Ulleng basin, is over 10 Km in thickness. An understanding of the marine Yeonil Group in the Pohang Basin may provide insights into the hydrocarbon potential of the offshore East Sea regions. Heulandite, smectite, dolomite, kaolinite and opal-CT are commonly found as diagenetic minerals in the Yeonil Group. Among these minerals, heulandite occurs as a main cement only in sandstones consisting of volcanic matrix, Smectite composition and diagenetic mineral facies such as heulandite and opal-CT may reflect that the Yeonil Group has undergone shallow burial, temperatures below about 60 degrees. This suggest that sandstones have experiened weak diagenetic alteration. In order to reconstruct the thermal history of the basin, apatite fission-track analysis was carried out. Aapparent apatite fission-track ages (AFTAs) exhibit a broader range of ages from 238 Ma to 27 Ma with mean track lengths in the range of $15.24\pm8.0$ micrometers, indicating that these samples had undergone significant predepositional thermal alteration. The Triassic to Cretaceous AFTAs seem In represent the timing of cooling of their sedimentary sources. Late Cretaceous mean AFTA $(79.0\pm8.0 Ma)$ on the Neogene Yeonil Group indicates that the Yeonil Group had not been buried deeper than 2km since its deposition. The organic matters of. the Pohang Basin remain in the immature stage of thermal evolution because burial depth and temperature were not sufficient enough for maturation even in the deep section of the basin.