Jindong Formation Research Articles

A small sauropod trackway from the Upper Cretaceous Jindong Formation (Cenomanian), Goseong County, South Korea

In 2000, a small sauropod trackway was discovered in the Upper Cretaceous Jindong Formation (Cenomanian) at Eosin-ri, Goseong County, South Korea. This quadrupedal trackway consists of 34 very small sauropod footprints, with an average manus width of 10.0 cm and pes length of 12.8 cm, showing low heteropody (mean IPS/IMS: 1.38). The manus tracks are oval to kidney-shaped, while the pes tracks are generally subcircular to V-shaped, lacking distinct claw marks. The trackway shows a medium to wide gauge (mean PTR: 38.8 %; WAP/PL: 1.18). The small footprint size and estimated trackmaker body size suggest that the trackmaker was an early juvenile titanosauriform sauropod based on the contemporaneous sauropod taxa of East Asia. Sauropod trackways reported from the Jindong Formation, including the Eosin-ri trackway, exhibit a tendency for narrower trackway gauges as pes length increases. This negative correlation between trackmaker size and trackway gauge may imply ontogenetic or behavioral variations within the same clade of sauropods or differences in gait or body plan amongst different sauropod taxa.

Fish swim traces from the Jindong Formation (Cretaceous) Korea: Implications for lake basin ichnofacies and paleoecology

The track rich Cretaceous Jindong Formation is famous for abundant tetrapod track assemblages, which occur at multiple, closely-spaced stratigraphic levels in the Gyeongsang Basin lake deposits of South Korea. However, until now no fish traces or fish body fossils had been reported. Thus, the discovery of three Undichna ichnospecies (U. simplicitas, U. bina, and U. britannica) provide the first direct evidence of fish in the basin. Paired in-phase traces vary in width and indicate a range of fish sizes among the tracemakers. Undichna assemblages represent a shallow lacustrine Undichna ichnocoenosis. Bird tracks (Ignotornis) registered on the same surface represent the superposition of a shorebird ichnocoenosis. Dinosaur tracks (Brontopodus and Caririchnium) associated with surfaces only ∼1 m below the bird and fish traces, represent additional large tetrapod ichnocoenoses, and demonstrate multiple, superimposed ichnocoenoses, interpenetrating localized sedimentary successions which are little separated in space or time. The Undichna and shorebird, ichnocoenoses are considered, in schema followed here, as representative of higher-level ‘archetypal’ Charachichnos and Grallator ichnofacies respectively. However, it is not clear whether a third ichnocoenosis and ichnofacies is represented by the Brontopodus and Caririchnium assemblages or the extent to which the overprinting of different ichnofaunas in localized areas always allows for the unambiguous application of ichnocoenois and ichnofacies schema.

Detrital Zircon U-Pb Geochronology and Hf Isotope Geochemistry of the Hayang Group, SE Korea and the Himenoura and Goshoura Groups, SW Japan: Signs of Subduction-Related Magmatism after a Long Resting Period

There was a hiatus in magmatism in Korea and Japan, located on the eastern continental margin of Asia, during a period of about 40 Ma from 160 Ma to 120 Ma. The cause of the resumption of magmatism since then is not yet well understood. In this study, we analyzed the Hf isotope composition of detrital zircons in the Cretaceous sediments of Korea (Hayang Group) and Japan (Goshoura and Himenoura groups) to investigate the tectonic evolution of eastern Asia in the Early Cretaceous period. εHf(t) in Cretaceous zircons from Japanese samples values from +8.2 to +0.1, suggesting that magmatism was sourced from the depleted juvenile materials, which is compatible with ridge subduction and subsequent melting of the young oceanic crust. εHf(t) values from Cretaceous zircons in the Hayang Group are negative, except for the Jindong Formation, which had a sediment supply from Japan, indicating that the old continental crust material of the Korean Peninsula was included in the magma generation. The detrital zircons of this study exhibit a depleted isotopic character at the beginning of subduction-related magmatism in Permian and Early Cretaceous, and then gradually change to a more enriched composition. This trend may be a typical example of the Pacific-type orogenic cycle.

경상누층군 진동층에 발달한 양방향성 고수류 기록: 산상과 고환경적 의미

경상누층군 진동층에 발달한 양방향성 고수류 기록: 산상과 고환경적 의미

Nature and evolution of the Cretaceous basins in the eastern margin of Eurasia: A case study of the Gyeongsang Basin, SE Korea

The Gyeongsang Basin is the largest among the non-marine Cretaceous sedimentary basins in Korea and Japan, formed by sinistral strike-slip movement induced by the oblique subduction of the paleo-Pacific plate under the eastern Asian continental margin, and has an evolutionary history of about sixty million years. SHRIMP and LA-MC-ICPMS U-Pb analyses were performed on the detrital zircons separated from the constituent formations of the Gyeongsang Basin. We determined the maximum depositional ages of the four formations based on their ages of the youngest groups as follows; 118.0 ± 2.6 Ma (n = 4) for the Hasandong Formation, 108.7 ± 0.8 Ma (n = 11) for the Chilgok Formation, 106.0 ± 0.2 Ma (n = 63) for the Silla Conglomerate, 105.4 ± 0.4 Ma (n = 14) for the Haman Formation, and 99.9 ± 0.7 Ma (n = 5) for the Jindong Formation, belonging to the period from Aptian to Cenomanian. The pre-Cretaceous detrital zircons of the lower to middle Gyeongsang Supergroup indicate their derivation from the Yeongnam Massif and the Okcheon Metamorphic Belt surrounding the Gyeongsang Basin. At around 115 Ma, as reflected as enhanced proportion of such ages in the detrital zircons and occurrence of farther inland igneous activities, the tectonic environment of Gyeongsang Basin changed to intra-arc due to the more active reestablishment of subduction-related igneous activity. However, the upper Gyeongsang Supergroup has a new age component of the mid-Permian, along with changes in the direction of paleocurrent flowing from the northeast and east, indicating sediment supply from SW Japan with rocks of that age. The changes in the direction of the paleocurrent flow seem to indicate that the center of igneous activity has moved in the direction of the subduction zone to the east. As the intensity of igneous activity continued to increase, the Gyeongsang Basin was closed by the filling of the basin by volcanic activity. The Cretaceous basins of the Korean Peninsula and southwest Japan show similar evolutionary histories, suggesting a type model of the creation and the evolution of basin around the continental margin subduction zone; creation of sedimentary basin by pull-apart or rifting in the backarc region, evolution to intra-arc basin by the landward progress of subduction-related igneous activity, and finally the closure of the basin due to the advent of highly enhanced igneous activity.

A New Semi-Palmate Bird Track, Gyeongsangornipes lockleyi ichnogen. et ichnosp. nov., and Koreanaornis from the Early Cretaceous Jindong Formation of Goseong County, Southern Coast of Korea

Well-preserved semi-palmate bird tracks and small wading bird tracks from the Early Cretaceous Jindong Formation of Deokmyeongri, Hai-myeon, and Naesanri, Donghae-myeon, Goseong County, South Gyeongsang Province, southern coast of Korea, are herein described as Gyeongsangornipes lockleyi ichnogen. et ichnosp. nov. and Koreanaornis hamanensis, respectively. Gyeongsangornipes lockleyi is a small asymmetrical, strong mesaxonic bird track, about 31–32 mm long and 40–41 mm wide, without a clear hallux impression. Divarication between digits II and III is much larger than that between digits III and IV. Webbing is clearly preserved, and the web between digits II and III is smaller than that between digits III and IV, which shows strong asymmetry of web development. Two different-sized Gyeongsangornipes lockleyi appear to suggest two different-size classes of web-footed birds. Koreanaornis hamanensis is a small sub-symmetrical wading bird track, about 26–28 mm long and 29–39 mm wide, without clear hallux impressions. The divarication between digits II and III (59°–66°)°) is larger than that between digits III and IV (44°– 58°). Divarication between digits II and IV is 103°–123°. Length of digit III (26–28 mm) is longer than those of digits II and III (about 18 mm). These new records shed light on patterns of bird track diversity and abundance in the Cretaceous of Korea and document a diverse avian fauna that flourished during the Cretaceous.

The Trackway of a Quadrupedal Ornithopod from the Jindong Formation (Cretaceous) of Korea

We report the first occurrence of the trackway of a quadrupedal ornithopod from the Jindong Formation (Late Aptian) of Korea. Although trackways of ornithopods are abundant in the Cretaceous of Korea, especially in the Jindong Formation, trackways of a quadrupedal trackmaker have never been reported from Korea. Moreover, the manus shows an unusual morphology with three subcircular indentations arranged in an unusual, elongate arc unlike any seen in other ornithopod ichnospecies. The specimen is clearly different from all other known Korean ornithopod footprints and is herein named as Caririchnium kyoungsookimi. To date, Caririchnium is one of only two ichnogenus names applied with confidence to Lower Cretaceous ornithopod tracks from Asia.

GIS를 이용한 경남-울산-부산지역 구성암류의 지질시대별 및 암층별 분포율과 분포특성

암석자원, 산업부지 및 개발계획 등의 지질정보자료로 활용될 수 있도록 분석된 경남, 울산 및 부산지역 구성암류의 지질시대별 암층별 분포율 및 특성은 디음과 같다. 이를 위하여 ArcGIS 9.3, 1 대 250,000 수치지질도 및 수치지형도가 이용되었다. 경남지역의 구성암류는 모두 6개의 지질시대로 구분된다. 분포율은 백악기, 선캠브리아기, 제4기, 쥬라기, 삼첩기 및 제3기의 순으로 감소하고 1.35-57.36%의 범위값을 이루며 그중 전자인 백악기에서 가장 큰 값을 가진다. 구성암층은 모두 40개이며, 그 중 24개가 1.15-13.64%의 다소 좁은 범위 그리고 도합 94.58%를 가져 거의 대부분을 차지한다. 여기에서 가장 우세한 안산암 및 안산암질 응회암은 경남지역의 북동부, 중동부와 남부일대에 발달하며 주변암과 심하게 굴곡진 경계면을 이룬다. 울산지역의 구성암류는 3개의 지질시대로 구분된다. 분포율은 백악기 제4기 및 제3기의 순으로 감소하고 6.90-79.21%의 넓은 범위값을 이루며 전자에서 그 값이 크게 증가한다. 구성암층은 모두 1l개이며, 그 중 9개가 1.50-39.0%의 다소 넓은 범위 그리고 도합 98.63%를 가져 그 대부분을 차지한다. 이 중 가장 우세한 진동층은 울산지역 내측부와 동부 일대에 넓게 발달한다. 부산지역 구성암류는 3개의 지질시대로 구분된다. 분포율은 백악기, 제4기 및 제3기의 순으로 감소하며 6.73-47.02%의 범위값을 이루며 전자 둘에서 88.03%를 가져 그 대부분을 차지한다. 구성암층은 모두 10개이며 그 중 6개가 4.07-47.02%의 넓은 분포범위 그리고 도합 93.02%를 가져 거의 대부분을 차지한다. 이 중 뚜렷하게 우세한 충적층은 낙동강 하류, 서낙동강 및 수영강 일대에 발달한다. To get the geologic information data such as rock resources, industrial ground, development planning and so on, distribution ratios of constituent rocks with geologic age and rock type were obtained in Gyeongnam, Ulsan and Busan areas by ArcGIS 9.3 program, digital geologic and geomorphic maps of 1 : 250,000 scale. Geologic ages and rock types in the Gyeongnam area can be divided into 6 and 40, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Precambrian, Quaternary, Jurassic, Triassic and Tertiary. They show the wide ranges of 1.35-57.36%, and the former makes the most dominant ratio. Major rock types are 24 ones, all of which occupy the ratio of 94.58% and relatively narrow ranges of 1.15-13.64% in the area. Among them, andesite and andesitic tuff shows the more or less dominant ratio, and separately develops in the northeast, mid east and south parts of the area. In the Ulsan area, geologic ages and rock types can be divided into 3 and II, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Quaternary and Triassic. They show the very wide range of 6.90-79.21%, and the former makes the most prevailing ratio. Major rock types are 9 ones, which totally occupy the ratio of 98.63% and more or less wide ranges of 1.50-39.01% in the area. Among them, Jindong formation shows the most dominant ratio, and widely develops in the inner and eastern part of the area. In the Busan area, geologic ages and rock types can be divided into 3 and 10, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Quaternary and Tertiary. They show the wide ranges of 6.73-47.02%, and the two former makes the most dominant ratio of 88.03%. Major rock types are 6 ones, all of which occupy the ratio of 93.02% and relatively wide ranges of 4.07-47.02% in the area. Among them, alluvium forms the most dominant ratio, which mostly develops in the lower Nagdong River, West Nagdong River and Suyeong River.

Early cretaceous bird-dominated and dinosaur footprint assemblages from the northwestern margin of the Junggar Basin, Xinjiang, China

Here we describe a number of mostly isolated bird and non-avian dinosaur footprints from the Huangyangquan track site in the Lower Cretaceous Lower Layer of the Tugulu Group near Huangyangquan Reservoir in the Wuerhe District, Karamay, Xinjiang Uyghur Autonomous Region, China. Bird footprints at the site pertain to Koreanaornis dodsoni n. ichnosp., Goseongornipes isp., Aquatilavipes isp., and Moguiornipes robusta n. ichnogen. n. ichnosp. Moguiornipes tracks may be the products of a bird with lobed feet. These shorebird-morph tracks are the first solid evidence of birds in the Tugulu Group, and greatly enrich the known faunal diversity of the Lower Layer of the Tugulu Group. The Huangyangquan avian ichnofauna is comparable to those of the Jindong Formation, Korea and the Dakota Formation, USA. Non-avian dinosaur footprints at the site pertain to cf. Jialingpus isp., Asianopodus isp., and Kayentapus isp. This is the first report of Jialingpus from Lower Cretaceous strata. The discoveries of Asianopodus isp. and Kayentapus isp. increase the known ranges of these two ichnogenera.

Dinosaur skin impressions from the Cretaceous of Korea: New insights into modes of preservation

Three specimens of sauropod dinosaur skin impressions from footprints in the Lower Cretaceous Jindong and Haman formations are unusual because they are not associated with well-preserved ‘host’ tracks. This suggests a hitherto unreported mode of preservation in which diagnostic but isolated skin traces may appear associated with substrates where only the superficial layers were originally soft. Two specimens from the Haman Formation of Gainri and Sinsu Island reveal large pentagonal to heptagonal scale impressions (size 2.0–2.5 cm). Another specimen from the Jindong Formation of the Deokmyeongri area is an extremely well-preserved, honeycomb-like pattern of hexagonal scale impressions, but an adjacent part reveals pentagonal to heptagonal polygons of variable size. Collectively these skin impressions more than double the sparse record of sauropod skin impressions and show that patterns (morphology) are consistent from the Jurassic to the Cretaceous. Although comprehensive syntheses have yet to be attempted, skin traces are amendable to systematic description using tubercle size, shape, thickness, and inter-tubercle groove thickness. Such features are useful for distinguishing the different morphologies of dinosaurs and other vertebrates that lived in Korea and other regions during the Mesozoic. Dinosaur skin impressions have occasionally been confused with glypogryptids, typical deep sea feeding traces, small desiccation cracks, and small load casts which they superficially resemble. To avoid such confusion we enumerate criteria useful for distinguishing dinosaur skin impressions from similar shaped invertebrate trace fossils and inorganic sedimentary structures. These criteria vary in importance but include preservation, morphology, dimension of morphology, depositional environment, deformation of underlying sediments, uniformity of size and shape of individual scale impressions within single specimens, ornamentation, and geological age.

New dinosaur tracks from Korea, Ornithopodichnus masanensis ichnogen. et ichnosp. nov. (Jindong Formation, Lower Cretaceous): implications for polarities in ornithopod foot morphology

Twelve trackways of ornithopods from Lower Cretaceous lacustrine margin deposits of the Jindong Formation represent new dinosaur trackways described from Korea. The site, discovered during highway construction, was rescued by removing the most important trackways to the Korean Natural Heritage Center in Daejeon, where they are on permanent display. The new ichnotaxon Ornithopodichnus masanensis ichnogen. et ichnosp. nov. is recognized as a distinctive robust tridactyl track, slightly wider than long (l/w ratio = 0.91), with positive (inward) rotation. The toe prints are very thick, broad and U-shaped, resulting in a trefoil outline with a smoothly rounded hind margin. Digit III is short and projects anteriorly much less than digit II and IV (= weak mesaxony). Divarication of digits II-IV is about 70° with interdigital angle II-III larger than III-IV. Trackway width is narrow and the stride length/track length ratio is about 4.2–4.6. The Ornithopodichnus trackways evidently represent gregarious blunt-toed Iguanodon-like bipedal ornithopods, although poorly preserved manus traces are discerned in a few trackways. Ornithopodichnus is distinct from other well known iguanodontid tracks that display much stronger mesaxony and indicates a polarity in ornithopod foot morphology that can be verified by reference to known foot skeletons.

Traces of evaporites in Upper Cretaceous lacustrine deposits of Korea: Origin and paleoenvironmental implications

Diverse types of halite and sulfate evaporite traces occur in the Upper Cretaceous lacustrine deposits of the Jindong Formation and the Jangdong Tuff in Korea, in which dinosaur tracks are common. The halite traces usually occur as casts or moulds, and they include traces of primary halite hoppers, primary and intrasedimentary skeletal halite, and intrasedimentary tiny halite. The sulfate traces occur as intrasedimentary and displacive casts filled with sediments and sparry calcite, and the casts occur as diverse modes from single crystal casts through nodular aggregates to massive aggregates. Some aggregates of the sulfate casts are aligned in crack pattern, and selective occurrence of the laths in ripple troughs are observed. Soluble sulfate evaporite minerals such as gypsum, glauberite, or mirabilite are probable for the precursors of these traces. These halite and sulfate traces are interpreted to have been formed in a saline lake and mudflats. It is interpreted that meteoric water was responsible for the evaporite precipitation in the Jindong Lake and Jangdong Lake. Recycled brine produced by the repeated dissolution of evaporites might contribute to the evaporite precipitation in the paleo-Jindong Lake and the paleo-Jangdong Lake. The development of saline lake deposits in the Jindong Formation and the Jangdong Tuff suggests that the southern part of the Korean Peninsula remained an inland continental area during the Cretaceous resulting in semi-arid paleoclimatic condition due to an orographic effect by the location of the Korean Peninsula on continental margin in mid-latitude with topographic barriers during the Cretaceous. The occurrence of dinosaur tracks in the lake margin deposits of saline lake with frequent inflow of dilute meteoric water suggests that Upper Cretaceous dinosaurs inhabiting lakes on the Korean Peninsula might have drunken brackish water.

Playa lake and sheetflood deposits of the Upper Cretaceous Jindong Formation, Korea: Occurrences and palaeoenvironments

Lake model of the Upper Cretaceous Jindong Formation in Korea was established on the basis of sedimentological and palaeobiological records of the playa lake and sheetflood deposits and their palaeoenvironmental implications. The playa lake and sheetflood deposits of the Jindong Formation are characterized by the common presence of traces of vanished evaporites, complicated polygonal desiccation cracks and rainprints, the pedogenic carbonate development, and the preservation of invertebrate traces and dinosaur and bird tracks. The traces of vanished evaporites including halite and sulphate evaporite occur as evaporite pseudopmorphs and moulds. The occurrence of all of the evaporite minerals as traces suggests that flooding stages persisted much longer than evaporation and desiccation stages. Invertebrates, birds, and dinosaurs inhabited the playa lake environment of the Upper Cretaceous Jindong Lake. The Jindong Lake formed by the combination of humid source area and arid depositional site due to an orographic effect in fault-bounded basin. Extensive development of the playa lake and sheetflood deposits with evaporite mineral casts and very limited association of shoreline deposits in the Jindong Formation are characteristic of closed lake, and the Jindong Lake is compared to a lake formed in partly drained closed basin. The aggradation of mudflat deposits indicates continued subsidence of the basin and continuation of an underfilled lake basin. The Jindong Lake expanded and stabilized as a playa lake surrounded by dry to saline mudflats, and palaeoclimate and subsidence rates changed little throughout the period of the Jindong Lake development.

Dinosaur-dominated footprint assemblages from the Cretaceous Jindong Formation, Hallyo Haesang National Park area, Goseong County, South Korea: Evidence and implications

The track-rich Cretaceous Jindong Formation comprises part of an intra-arc basin, fluvio-lacustrine succession that represents a late stage in the evolution of the Kyongsang Basin. This formation is replete with track-bearing levels indicating the activity of many generations of dinosaurs and birds. The track-rich beds occur in the upper part of the Hayang Group (Kyongsang Supergroup), which also contains other, underlying dinosaur-track-bearing formations. However the Jindong Formation and underlying formations have produced few age-diagnostic body fossils. Altered volcaniclastic sediments such as are found the Jindong Formation complicate interpretation of the age of the tracks as discussed in the accompanying companion paper. Nonetheless such settings provided near optimal conditions for the formation and preservation of abundant track assemblages (ichnofaunas), and the Jindong Formation has become an ichnological “cause celebre” producing impressive statistics on the number of track-bearing sites, number of track-bearing levels and number of measured trackways. These data allow various inferences about certain aspects of the population structure, behavior and distribution of the dinosaurian track makers in these dinosaur-dominated paleocommunities. The Jindong Formation and underlying Haman Formation have also yielded many bird tracks. The complete lack of avian body fossils in Korea and the rarity of dinosaur skeletal remains means that the footprint record currently provides the vast majority of the Mesozoic vertebrate evidence available for the entire Korean peninsula. Thus, the tracks represent a highly significant addition to the national paleontological heritage of Korea, as well as being a very important component of the East Asian and global footprint records. Detailed studies of a 100–200-m-thick succession at the Sangjok Dinosaur Tracksite National Monument in the Hallyo Haesang National Park area in Kosong County reveal an average of about two track-bearing levels per meter, making it one of the richest track-bearing sections on record and providing evidence of the activity of hundreds of individuals. Many other track sites are found locally in the Jindong Formation in Kosong County (about 500 km 2) including one described herein from near Gohyeon village where the Jindong Formation type section is situated. Other track sites can be traced laterally over larger distances within the Gyeongsang Basin. The composition of ichnofaunas throughout this region appears remarkably consistent. The Jindong Formation is one of the few localities where sauropod, ornithopod, and bird tracks all occur in abundance, probably due to latitudinal/climatic controls. The sauropod tracks, which include wide-gauge forms allied to Brontopodus, form the largest brontosaur trackway sample yet reported but are characterized by a high proportion of small individuals. Such unusual size-frequency distributions raise interesting ecological and taphonomic questions about the biasing of the body fossil record towards large individuals by various physical (preservational) or biological/ ecological controls. The most abundant dinosaur trackways are those of iguanodontids (cf. Caririchnium or Iguanodontipus) that often traveled in herds. By contrast, sauropod tracks show little or no evidence of gregarious behavior and rarely occur on the same bedding planes as ornithopod trackways. This suggests a pattern of mutual exclusion or geological segregation between these two herbivore groups, which indicates that they probably frequented the area at different times. Sauropod and ornithopod track size-frequency distributions are also fundamentally different, suggesting that the ornithopods were mainly sub-adults and adults, whereas the sauropods were predominantly juveniles. Theropod tracks are uncommon suggesting a low predator:prey ratio of 1:20. Bird tracks including the large ichnospecies Jindongornipes kimi, an intermediate-sized form, Goseongornipes markjonesi ichnosp. and ichnogen. nov., and a small ichnospecies Koreanaornis hamanensis occur at several dozen stratigraphic levels in association with nematode trails ( Cochlichnus) and other invertebrate traces. These three ichnospecies are assigned to the respective ichnofamilies Koreanornipodidae ichnofam. nov., Ignotornidae, and Jindongornipodidae ichnofam. nov. All these avian footprints are typical of bird track assemblages in lake shoreline deposits, and indicate the activity of many generations of waders or shorebirds. We also recognize other, much less common, small footprint types tentatively attributed to a perching bird or a diminutive theropod. Collectively the bird tracks indicate the considerable potential of avian ichnites to provide insight into avian paleoecology at an early stage in the evolution of Class Aves.

Life in an active volcanic arc: Petrology and sedimentology of dinosaur track beds in the Jindong Formation (Cretaceous), Gyeongsang Basin, South Korea

The Jindong Formation was deposited as a thick succession of fine-grained volcaniclastic sediments in a rapidly subsiding intra-arc basin. These sediments contain abundant dinosaur and bird tracks that occur on many bedding planes throughout the approximately 110 m of stratigraphic section measured for this study. The main lithologies in the Jindong Formation are ash-rich mudstone, siltstone, and very fine sandstone. Minor lithologies are coarser sandstone, conglomerate, carbonates, and ash tuff. The sandstones are feldspathic and lithic arenites and wackes. They contain plutonic feldspars, volcanic rock fragments, volcanic ash, and a variety of quartz types. All lithologies show evidence of extensive post-depositional alteration, including devitrification and replacement of detrital grains by authigenic minerals. The alterations are typical of burial metamorphism with high heat flow. Sediments of the Jindong Formation can be grouped into three facies associations. Association 1 (proximal) comprises 16% of the measured sections. It consists of various types of bedded, cross-bedded, laminated, and ripple cross-laminated sandstone and minor conglomerate. These are interpreted as fluvial or distributary channel and proximal lake deposits. Association 2 (medial) comprises 53% of the measured sections. It consists mainly of heterolithic couplets of very fine sandstone and mudstone that are mm to dm thick. They contain graded bedding, laminations, current ripples, wave ripples, and mud cracks, and are interpreted as lacustrine hyperpycnal flow deposits. Association 3 (distal) comprises 31% of the measured sections. It consists mainly of bedded shale, mudstone, and siltstone. These are interpreted as distal lake deposits. Associations 2 and 3 contain minor carbonates, which are interpreted as lacustrine and/or diagenetic in origin, and minor tuffs, which are interpreted as tephra. Small wave ripples, dinosaur tracks, invertebrate burrows, and mud cracks are common throughout the measured sections; thus the Jindong lakes are inferred to have been shallow and ephemeral in nature. Wave ripple-crest orientations are consistently WNW-ESE, indicating a prevailing wind direction from the NNE or SSW. Because the sediments are mostly fine-grained and the ash beds thin, the study area is inferred to have been in a distal lowland setting, at least tens of km away from erupting volcanoes. Paleoclimate reconstructions suggest that the study area had a seasonal climate with wet summers and dry winters. Cooler, wetter conditions are thought to have prevailed to the north, and warmer, drier conditions to the south. Modern volcanic arc environments with seasonal and/or humid climates are characterized by rapid aggradation of ashy sediment that fills drainages and causes widespread flooding. This style of sedimentation accounts for the facies found in the Jindong Formation, as well as the many bedding-plane exposures of tracks. The unusual occurrence of both sauropod and ornithopod tracks in the Jindong sections may be the result of a climate boundary that existed in the area at the time. Facies analysis of track types indicates that various track makers had the same environmental preferences, and facies association 2 contains the greatest number of tracks of all types. It is inferred that the tendency for only one track type to occur on a given bedding plane is the result of different types of animals visiting the study area at different times, rather than differing environmental preferences. The Jindong Formation contains an abundance of subaqueously deposited facies, an abundance of tracks, and many track levels that were wet when animals were walking on them. These features are not consistent with previous interpretations of aridity during Jindong time.

Palustrine calcretes of the Cretaceous Gyeongsang Supergroup, Korea: Variation and paleoenvironmental implications

Abstract Mostly siliciclastic lacustrine deposits from five stratigraphically different formations (Jinju Formation, Jindong Formation, Geoncheonri and correlative Hwasan Formations and Dadaepo Formation, in ascending order) in the Cretaceous Gyeongsang Basin, Korea, were examined for aspects of lithofacies and pedogenesis to evaluate the relative influence of geological controls on the development of palustrine calcretes (calcretes formed from palustrine deposits). The pedogenic carbonate development of palustrine deposits in the Gyeongsang Supergroup varies from formation to formation. The highest development is in the Dadaepo Formation and the second is in the Jindong Formation. The lowest development of palustrine calcretes is in the Geoncheonri and Hwasan Formations and the Jinju Formation shows intermediate development. The more negative d13C values and the less negative d18O values of the Dadaepo palustrine calcretes confirm greater pedogenic development in the Dadaepo Formation. That the highest development was in the Dadaepo Formation was attributed to it having the smallest lake size, indicating that lake size is critical to palustrine calcrete development in non‐carbonate lakes under semi‐arid climate. In spite of having the largest lake size, the higher development in the Jindong Formation could have resulted from its lowest lake gradient and most arid paleoclimate. The higher development of palustrine calcretes in the Late Cretaceous deposits (Jindong Formation) than the Early Cretaceous deposits (Jinju Formation) reflect overall increase in aridity throughout the period during the deposition of the Gyeongsang Supergroup. Consequently, the diverse development of the palustrine calcretes in the Gyeongsang Supergroup indicates that the lacustrine settings varied in time and space throughout the evolution of the Cretaceous Gyeongsang Basin. Such variation in palustrine calcrete development according to the change in paleoenvironments may provide a basis to interpret the relative paleoenvironmental condition of lacustrine deposits including paleoclimate, lake size and gradient.

Dinosaur track-bearing deposits in the Cretaceous Jindong Formation, Korea: occurrence, palaeoenvironments and preservation

Dinosaur track deposits of the Upper Cretaceous Jindong Formation, Korea, were examined from a sedimentological viewpoint to interpret their palaeoenvironments and conditions of preservation. The general depositional environment of the Jindong Formation was lake-margin to shallow lacustrine. Lake-margin deposits comprise most of it but the stable isotope values of the carbonates suggest an open lake. There are two types of dinosaur track beds. One is a discrete trackway deposit and the other is a dinoturbated deposit. All of the dinosaur trackways in the formation are preserved in interlaminated fine-grained sandstone to siltstone-mudstone deposits, which were deposited on a dry mudflat at the lake margin by sheetfloods and then underwent calcareous pedogenesis. The dinoturbated deposit was originally calcareous silty mud, reflecting deposition in a shallow lake of low energy. It was also modified later by calcareous pedogenesis. The trampling traces of dinosaurs in the Jindong Formation are recognized both on bedding surfaces and in sections. In places dinosaur tracks occur as ‘overtracks’ which are preserved in layers above the true tracks. The Jindong dinosaur track deposits are usually associated with pedogenic calcretes, which indicates that the climate at the time was seasonal and arid. Consequently, it is interpreted that the extensive and frequent preservation of dinosaur tracks in the Jindong Formation is the result of repeated deposition by sheetfloods on a mudflat associated with a perennial lake, which was utilized by dinosaurs as a persistent water source during drought, and subsequent development of calcareous pedogenesis in an arid climate.

Cretaceous stratigraphy and geologic history of medial Kyongsang Basin: tectonics and volcanism

The Palgongsan Fault comprises growth fault, dormant, and strike-slip phases. The strike-slip phase is manifested by the Palgongsan strike-slip fault, which sinistrally offsets the Palgongsan Granite and the earlier strata. The Palgongsan strike-slip fault shows various amounts of slip within the extent of the fault, but the maximum observed slip is about 5.5 km as measured in the Hasandong Formation. During the earlier phases of the Palgongsan Fault, faulting, sedimentation, and igneous activity were inter-related. Identifications of other major faults have enhanced the local stratigraphic study. A border area astriding the Milyang and the Uisong subbasins shows complicated stratigraphy reinforced by the lateral encountering of the stratigraphic schemes of the two subbasins. The stratigraphic complexity is exemplified by the Jindong Formation which is ramified, into local stratigraphic units, the uppermost one being the Konchonri Formation. In spite of doubts on their stratigraphic relationship, our observations prove that the Konchonri Formation overlies the Chaeyaksan Volcanic Formation. The chronological sequence of the volcanisms in the Kyongsang Basin has been summarized.

Dinosaur tracks in intrusive igneous rock

Well preserved brontosaur footprints are replicated as impressions at the top of a dacitic igneous sill that intruded the track‐rich Cretaceous Jindong Formation, Kyeongsang basin South Korea. Although an unusual occurrence, the example shows the potential of such intrusions for enhancing preservation of trace fossils in some cases

The track record of Mesozoic birds: evidence and implications

The occurrence, systematics, palaeobiological and evolutionary significance of Mesozoic bird and birdlike tracks are reviewed in the light of recent new discoveries in East Asia, Africa and North America. The most abundant footprint evidence currently comes from Lower Cretaceous deposits of East Asia and North America, where there is now a substantial track record for shorebirds. However, there is also a significant record of pre-Cretaceous bird-like tracks. The Cretaceous Jindong Formation of South Korea has recently yielded over 30 localities and stratigraphic levels, tripling the previous record worldwide and providing evidence of hitherto unknown large waders: Jindongornipes kimi ichnogen. et ichnosp. nov. Like other previously named ichnotaxa, this bird track type probably represents a charadriiform species. It is included with Ignotornis and Koreanaornis in the new ichnofamily Ignotornidae. Lower Cretaceous bird tracks are abundant, typically show high densities (100-300 tracks m 2 ) and often occur in association with invertebrate traces, inferred to have been made by the organisms on which the birds were feeding. Such track evidence suggests that waterbird communities were well-established by the end of the Early Cretaceous. This is about 30 Ma before the purported waterbird radiation inferred from Upper Cretaceous avian skeletal remains, but is consistent with hypotheses that suggest an ancestral shorebird stock. Bird and bird-like tracks from the Jurassic and Late Cretaceous are variable in morphology, still poorly understood, and sometimes attributed to small coelurosaurian dinosaurs. However, current evidence suggests that the Jurassic aviform ichnogenus Trisauropodiscus may be of avian origin. It is sufficiently distinct from typical grallatorid (coelurosaurian) tracks to warrant recognition of a new ichnofamily (Trisauropodiscidae), which includes the newly described ichnospecies Trisauropodiscus moabensis from North America. Bird and bird-like tracks from both the Jurassic and Cretaceous are shown to be much more abundant and distinctive than previously supposed. Moreover, they add significantly to our understanding of early avian evolution and palaeoecology, and provide insights into the timing of events in avian evolution.