• Proceedings of the KSEEG Conference
• /
• 2005.04a
• /
• pp.333-336
• /
• 2005

• Journal of the Korean earth science society
• /
• v.43 no.3
• /
• pp.405-429
• /
• 2022

Detrital zircon LA-MC-ICP-MS U-Pb dating of the Cretaceous Gurye Group, Gurye Basin, was carried out. Gurye Group consists of Supyeongri, Geumjeongri, Togeum, and Obongsan formations in ascending order, and five samples were collected for age dating. Based on the dating results, the lowermost Supyeongri and the uppermost Obongsan formations show narrow age ranges. Only Precambrian and Late Cretaceous zircons were found in the Supyeongri and Obongsan formations, respectively. However, the upper and lower Geumjeongri, and Togeum formations show wide age ranges from the Precambrian to Cretaceous. The youngest detrital zircon U-Pb ages of each formation except the Supyeongri Formation, which lacks Cretaceous zircon, were calculated to be ca. 107.4 Ma in the lower Geumjeongri Formation, ca. 104.6 Ma in the upper Geumjeongri Formation, ca. 97.7 Ma in the Togeum Formation, and ca. 88.5 Ma in the Obongsan Formation. Such results indicate that the depositional age of the Gurye Group can be constrained from the Lower Cretaceous Albian to the Upper Cretaceous Coniacian. Based on the distribution of the detrital zircon ages from each formation, the source area of the Gurye Group is interpreted to have been extended from the adjacent Youngnam Massif to the Okcheon Belt throughout the basin evolution. The increase of the Cretaceous zircon with time is thought to reflect the slab roll-back of the proto-Pacific plate during the Cretaceous.

• 한국지구과학회:학술대회논문집
• /
• 2005.02a
• /
• pp.126-134
• /
• 2005

최근 중생대 전기 백악기(약 1.2Ma) 지층이 분포하는 경북 고령의 지역에서 대량으로 발견된 골설목(骨舌目, Osteoglosomorpha) 어류화석을 기재하고 특징을 살펴본 후 현생골설목과의 관계를 조사하고, 아울러 다른 나라에서 발견된 것과의 비교연구를 통해 우리나라에서 발견된 어류화석의 고생물학적 의의를 살펴보았다. 경상층군에서 발견된 어류 화석군은 Semionotiformes, Amiiformes목, 골설목, 당멸치목(Elopiformes), 여을멸목(Albuliformes), Ichthyodectiformes목 등으로 구성되어 있으며, 그중 골설목(Osteoglossiformes)과 여을멸목(Albuliformes)이 가장 풍부하다. 경상어류화석군은 한국의 중생대 백악기 지층에서는 유일한 어류화석군이다. 또한 어류화석과 함께 발견된 여러 화석 및 지질학적 자료를 토대로 어류화석 서식 당시의 고환경을 유추하였다.

• 한국지구과학회:학술대회논문집
• /
• 2006.02a
• /
• pp.226-226
• /
• 2006

• Journal of the Korean earth science society
• /
• v.33 no.7
• /
• pp.618-626
• /
• 2012

The Cretaceous fossil sites of Seoyuri in Hwasun was designated as the Korean Natural Monument No. 487 in November 2007. It provides important resources for paleoenvironmental studies, including theropod trackways, plant fossils, mudcracks, ripple marks, and horizontal bedding. The Cretaceous sedimentary strata contain a wide variety of volcanic pebbles, 5-40 cm in diameter in the lower portion and are overlain by the Late Cretaceous Hwasun andesite. Whole rock absolute K-Ar age determinations were performed on six volcanic pebbles from the Cretaceous sedimentary strata and on two samples from the overlaying Hwasun andesite. These ages indicate that the rocks belong to the period between the Turonian of the late Cretaceous (91-70 Ma) and the Pliocene age of the early Cenozoic ($63.4{\pm}1.2$ and $62.1{\pm}1.2$ Ma). Thus, the K-Ar ages indicate that the maximum geological age of the dinosaur track-bearing sedimentary deposits is about ca. 70 Ma. Therefore, it suggests that the age is comparable to the formation ages of the dinosaur footprints-bearing deposits in Sado area of Yeosu (71-66Ma).

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

• Economic and Environmental Geology
• /
• v.34 no.1
• /
• pp.119-131
• /
• 2001

A mean characteristic remanent magnetization was obtained for the first time in Korea from volcanic and pyroclastic sedimentary rocks distributed in Haenam Area, located in southwestern part of the Korean Peninsula. The age of the prevailing rocks in this area belongs mostly to Late Cretaceous, with a few exceptions of Early Cretaceous, mainly based on K/Ar whole rock age dating. Characteristic remanent magnetizations of these have both normal and reverse polarities with antipodal direction, which were interpreted to be the primary remanent magnetizations obtained by the ambient Earth's magnetic field at the time of formation of the concerned rocks. The source magnetic minerals of the remanent magnetization has been identified as magnetite. The mean direction of characteristic remanent magnetization obtained from the Late Cretaceous rocks in this study is Dm/Im=21.4 supper(o)/57.1 supper(o) (${\alpha}_{95}=13.4^{\circ}$, k=350.0). The paleomagnetic pole position calculated from this result for the Late Cretaceous, is $72.5^{\circ}N/199.9^{\circ}E$ (dp/dm= $14.2^{\circ}/19.5^{\circ}E$), which matches well with those of 80 Ma ($76.2^{\circ}N/198.9^{\circ}E$) and 90 Ma ($76.2^{\circ}N/200.1^{\circ}E$) of the Eurasian Continent's APWP (Apparent Polar Wander Path). This result strongly indicates that the studied area, belonging to the Eurasian Continent, have suffered very little geotectonic movement after the Late Cretaceous. The deflection of declination of remanence from Early Cretaceous rocks in the study area may indicate that the micro-block was counterclockwisely rotated with vertical axis between the late of Early Cretaceous and the early of Late Cretaceous.

• Proceedings of the KGS Conference
• /
• 2002.11a
• /
• pp.97-100
• /
• 2002

지표의 기복은 암석의 차별적 풍화와 침식을 반영하므로, 기복의 형성에서 암석이 차지하는 몫을 이해하는 것은 중요하며 이 문제는 근대지형학의 발달 초기부터 중요하게 다루어져 왔다(권혁재, 2002).(Picture Omitted) 대구분지 북쪽 분수계를 이루고 있는 팔공산의 기반암은 중생대 백악기 말부터 제 3기초기에 걸쳐 백악기 퇴적암인 경상누층군을 관입하여 형성된 불국사화강암이다.(중략)

• Proceedings of the KSEEG Conference
• /
• 2005.04a
• /
• pp.329-332
• /
• 2005

• Proceedings of the KSEEG Conference
• /
• 2007.04a
• /
• pp.436-438
• /
• 2007