Shallow Lake Facies Research Articles

Long‐Term Landscape Evolution in Response to Climate Change, Ecosystem Dynamics, and Fire in a Basaltic Catchment on the Colorado Plateau

AbstractPredicting responses of semi‐arid to montane landscapes in southwestern North America to ongoing anthropogenic changes requires understanding of past interplay among geomorphic, ecologic, and climatic factors. This study utilizes modern weathering and sediment transport processes to inform the interpretation of a 250‐kyr lacustrine sediment record of paleoecology, hydrology, and erosion from a small, closed basin, basaltic catchment on the southwestern edge of the Colorado Plateau. Geochemical and mineralogical analyses of bedrock, colluvium, and lake sediments indicate that clastic sediments in the basin are a mixture of local physical weathering products (albite and ilmenite) and eolian dust (quartz, illite, and zircon). Dust fractions increase during glacial periods coincident with lower overall sedimentation rates, suggesting this pattern results from decreased local erosion rates and not increased dust deposition. Titanium counts from X‐ray fluorescence core scanning, a proxy for ilmenite content, traces past local erosion rates. The highest erosion rates, inferred from the highest Ti counts, follow climatic transitions toward interglacial conditions (Marine Isotope Stage 5e, 3a, and the Holocene), periods characterized by vegetation changeover (observed in the core's palynology), higher temperatures (piñon‐juniper‐oak pollen abundance), lower effective precipitation (shallow lake facies), and increased wildfire activity (microscopic charcoal particle counts and sizes). While brief inferred episodes of erosion occur following abrupt transitions to cooler and wetter conditions, indicated by the abundance of subalpine tree (spruce and fir) pollen and deeper lake facies, landscapes appear more stable during glacial periods. This long‐term perspective suggests that aridification and resulting vegetation succession and increased wildfires will increase erosion rates in similar settings regionwide.

Base-Level Fluctuation Controls on Migration of Delta Lobes: A Case Study from the Paleogene Shahejie Formation in the Huimin Depression, Bohai Bay Basin, NE China

Sandbody distribution patterns and controls are the most important foundation for petroleum exploration and development, particularly in a lacustrine basin with rapid changes in the sedimentary environment. To provide sedimentologists and petroleum geologists around the world with an analogue for sandstone reservoir prediction, the sedimentary facies of the fourth member of the Shahejie Formation (Sha-4 Member) in the Huimin Depression of the Bohai Bay Basin were analyzed, and the sequence stratigraphic framework was established based on characteristics of spontaneous potential logs and lithology. According to the findings of this study, the Sha-4 Member’s sedimentary environment was dominated by delta front and shallow lake facies. Delta front sandbodies were discovered to retrograde before prograding again throughout the established profile. The Sha-4 Member in the Huimin Depression is divided into a third-order sequence (LSC1), which can be further divided into four fourth-order sequences (MSC1 to MSC4), corresponding to the four sub-members (S4-1 to S4-4). During the development of the MSC1 to MSC4 sequences, the delta depositional scale first decreased and then increased with the changing base level. The maximum flooding surface developed within the MSC3 sequence. The Sha-4 Member sequence model reveals that the deltas in the study area exhibit self-similarity, and delta sandbodies are primarily developed in the MSC1, MSC2, and MSC4, whereas mudstone is largely developed in the MSC3.

Spatial and temporal cycle variations in the Eocene Lacustrine Green River Formation, Piceance Creek Basin, Colorado

Lithological cycles in the lacustrine Green River Formation of the Piceance Creek Basin, Colorado, vary spatially and temporally, and are challenging to correlate across the basin. In the center of the basin, lacustrine deposits contain bedded evaporites and kerogen-rich carbonate mudstone, whereas basin margin deposits contain alluvial sandstone, kerogen-poor mudstone, stromatolite, and mud cracks. Because coarsening upward cycles identified at the basin center differ significantly from cycles at the basin margin, exactly how cycle boundaries extend from one location in the basin to another is commonly unclear. In this investigation, eleven lithofacies are identified based on rock composition, sedimentary textures, physical sedimentary structures, biogenic structures, and chemical features. Lithofacies are grouped into four facies associations: (1) Alluvial Facies Association; (2) Shoreline Facies Association; (3) Shallow Lake Facies Association; and (4) Deep Lake Facies Association. Lithological cycles in the Green River Formation vary temporally and spatially, with each stratigraphic section preserving a record of deposition in a particular area of the basin as the Piceance lake evolved. To address the temporal and spatial variation of the cycles, multiple “type” cycles are described for each location in the study area. Facies associations and temporal stacking of cycles suggest that the Piceance lake was initially a deep, freshwater lake, following the Long Point transgression, as lake level rose above the Douglas Creek Arch to fill both the Uinta and Piceance Creek basins. Lake levels then stabilized but later began a period of increased fluctuation. Following basin closure, the Piceance lake became hypersaline under evaporative concentration conditions, precipitating nahcolite and halite at the basin center, with exposure of mudflats at the basin margin. The lake would remain this way until the Mahogany transgression deepened and diluted the lake. Together, facies associations and “type” cycles described in the Green River Formation lacustrine deposits reveal a record of lateral and vertical facies changes that occurred in the Piceance lake during its evolution.

Sedimentary characteristics of shallow-water delta and responses features in palaeoenvironment: a case study from the lower part of Neogene Minghuazhen Formation (Bonan area, Bohai Bay Basin, E China)

Shallow-water deltas are important reservoirs for hydrocarbon resources, and there are many oil and gas discoveries found in the sands in China. Many large shallow-water delta sedimentary systems were found in the Bohai Bay Basin in the Late Miocene. Several classic shallow-water deltas are developed in the early-stage sequence (SQmL2) of the lower part of Neogene Minghuazhen Formation in the Bohai Bay Basin which have attracted much attention in recent years. We choose the SQmL2 as an example to reveal the relationships between paleoenvironment and shallow-water delta facies and architecture. Analysis of 3D seismic data and logging data indicated that two types of sedimentary facies, including shallow-water delta and shallow lake facies, are developed during SQmL2. The shallow-water delta facies mainly consist of subaqueous distributary channel with mouth bar rarely developed. The deltas are mainly comprised of relatively thin (1–4 m) fine- to medium-grained sandstone. The combinations of distributary channels on planer view are mostly branch-shaped and lobe-shaped. The shallow-water deltas developed in SQmL2 are controlled by paleogeomorphology, sediment supply, and paleoclimate. The flat topography and sediment supply are favorable for sediments moving basinward for a long distance and forming channelized sand bodies. As the climate gets humid, the lake level rises and shallow lake area expands, resulting the sand bodies move landward and become much thinner. The lake level has changed from shallow to deep and to shallow, and correspondingly, sand body of subaqueous distributary channels has changed from lobe shape to branch shape and to lobe shape.

Fine evaluation and favorable area prediction of deep source rocks in northern Songliao Basin

Focusing on Xujiaweizi fault depression, the geological conditions and geochemical characteristics of deep natural gas formation in the north of Songliao basin are evaluated, the natural gas resources are estimated, and the favorable areas are optimized. Shahezi Formation shale is a set of coal bearing sediments with high organic matter abundance (TOC is 1%～12%), high over maturity (Ro is 1%～4%) and shore shallow lake facies, which are mainly distributed in Xujiaweizi fault depression, Gulong-Lindian fault depression and Yingshan fault depression. The thickness, TOC, Ro and hydrocarbon generation of four thirdorder sequences with different lithology (mudstone and coal) are carefully evaluated for the Shahezi Formation shale in the deep layer of Songbei. The comprehensive evaluation shows that the mudstone thickness of Es4 member in Anda and Xuzhong areas of Xujiaweizi fault depression is large (150 ~ 525m), TOC is high (1% ~ 4%), thermal evolution degree is high (Ro is 1.2% ~ 3.4%), and gas generation intensity is high (20 ~ 815) × 108m3 / t), moderate buried depth (3000~4500m) and overlapping area of 756km2. It is a favorable exploration area for natural gas and shale gas in Daqing Oilfield.

Analysis of logging parameter model of Jurassic complex reservoir in Xinjiang Shenquan Oilfield

The study discusses the characteristics of Jurassic reservoir in Shenquan Oilfield in Xinjiang. The reservoir of Qiketai Sanjianfang formation mainly develops delta front facies and shore shallow lake facies sand bodies.The lithological characteristics of the reservoir are mainly fine sandstone and siltstone, and the physical properties of the target layer are mainly medium porosity and medium permeability. The Jurassic reservoir space in Shenquan Oilfield is sandstone pore type, mainly composed of secondary pores, mainly including intergranular dissolved pores, intragranular dissolved pores and intercrystalline pores, with good connectivity between pores. According to the analysis data of well logging, core analysis, production performance and DST in Shenquan Oilfield, porosity, permeability and water saturation models are established respectively:The porosity interpretation model is established by using acoustic wave and shale content; the permeability parameter interpretation model is realized by applying graph based cluster analysis method and neural network algorithm. The oil saturation interpretation model is obtained by Archie formula. According to the logging interpretation model and interpretation results, it can meet the needs of reservoir evaluation, oil-water distribution and original geological reserve parameters. After analyzing the logging parameter model and reservoir parameter calculation method, it is considered that the Jurassic in the Shenquan Oilfield in Xinjiang has better physical properties.

Early Jurassic (Toarcian) warming identified from lacustrine sediments of eastern Liaoning, China

AbstractThis study focuses on the Tianshifu Basin, eastern Liaoning, China, which is filled with Lower–Middle Jurassic fluviolacustrine sediments rich in macroplants. Our aim is to explore the continental climate features of the late Early Jurassic period. The composition of the Early–Middle Jurassic flora and the carbon isotopic ratios of organic matter, total organic carbon, total organic nitrogen and sulphur of the rock samples from the Changliangzi section (the upper part of the Lower Jurassic deposits) have been investigated. Based on the flora, eastern Liaoning was generally characterized by temperate and humid conditions during the Early–Middle Jurassic period, but with rising temperatures during late Early Jurassic time. The sediments of the Changliangzi section show a transformation from shallow-lake facies to deep-lake facies. A positive organic carbon isotope excursion correlates with the deepening of this palaeolake, considered to be caused by climate warming. The late Early Jurassic climate warming indicated by floral and isotopic evidence corresponds to the climatic events recorded elsewhere in marine and continental sequences during the Toarcian Age, the so-called Toarcian Anoxic event, and may be associated with enhanced global greenhouse warming. This study provides new continental data supporting global warming during the late Early Jurassic period.

Sedimentary environment and geochemical characteristics of Shahejie Formation in Huimin Sag, Bohai bay basin, China

The Shahejie Formation in Huimin Sag is an important crude oil/natural gas reservoir stratum. The results show that (1) in the study area, the Sr/Ba value of Shahejie Formation ES4, ES3, and ES2 in Huimin Sag is 0.55–0.58, showing that these were freshwater-brackish water environment with a continental deposition; the average Sr/Ba value of the first member of Shahejie Formation (ES1) is 1.88, showing that it was a salt water environment. (2) B element method of paleo-salinity analysis shows that in ancient times, the salinity of ES1 was the highest; ES2 and ES4 had basically the same salinity that were lower than that of ES1; the third formation of Shahejie Formation(ES3) had the lowest salinity. (3) Analysis of values of Fe/Mn, Mg/Ca, and paleoclimate index C shows that the Shahejie Formation had generally a semi-dry climate. (4) Based on the analysis of the paleoenvironment, combined with the description of the cores, a sedimentary evolution model is built: ES4 was a debris flow fan-shaped river delta sediment in a shallow lake environment; ES3 was a delta-deep water fan-shaped system in a semi-deep-deep lake environment; ES2 was a delta system in semi-shallow lake environment; ES1 is the semi-shallow lake environment, the main sedimentary facies is the shore shallow lake facies.

KARAKTERISTIK ENDAPAN DANAU RAWA PENING DI MUARA INLET SUNGAI GALEH, KECAMATAN AMBARAWA, KABUPATEN SEMARANG

The Galeh River inlet estuary on Lake Rawa Pening is located in Ambarawa District, Semarang Regency. Sampling of Rawa Pening sediment at two points using modern coring methods. The coring results were observed and granulometric analysis was done using lazer scanning method with Master Sizer 2000. Core RWP-01 samples in the form of fine clastic sediments (Sand-Silt), reflecting the inlet river estuary environment in the hydrological lake system which is influenced by the fluvio-lacustrin process and showing characterizer of shallow lake facies. RWP-02 core samples in the form of fine-textured sediments (mud) rich in organic material, reflecting a relatively calm and stable depositional environment, formed by the density current mechanism that characterize the deep lake facies. The development of these sedimentary characters shows changes in sedimentary facies, namely shallow lake facies developing into clastical lake lacustrine into deep lake lacustrine facies.

Lake evolution and its influence on the formation of oil shales in the Middle Jurassic Shimengou Formation in the Tuanyushan area, Qaidam Basin, NW China

The non-marine Qaidam Basin is a petroliferous basin in northwest China. The Tuanyushan area is located in the Saishiteng Depression in the northern Qaidam Basin. Coal and oil shales are widely developed in the Middle Jurassic Dameigou and Shimengou formations in this area where the sedimentary sequence and controls on coal accumulation have already been well documented. However, the geochemical characteristics of lacustrine fine-grained sediments, including lacustrine oil shales, in the shale member of the Shimengou Formation and the main controlling factors of the formation of the oil shales are ambiguous. This paper aims to reconstruct the lake evolution history during the Middle Jurassic period and reveal its influence on the formation of the oil shales in this area. Oil shales and fine-grained sediments were systematically sampled to determine their mineralogical and geochemical characteristics (major, trace and rare earth elements; stable carbon and oxygen isotopes). Based on lithological variations and total organic carbon (TOC) contents, a complete third-order sequence is identified and can be further divided into four system tracts (lowstand system tract, LST; transgressive system tract, TST; highstand system tract, HST and regressive system tract, RST) that correspond to four lake evolution stages (A–D). Changes in the lake level show an initial shallow lake, followed by a continuous upward deepening trend, followed by a shallowing trend. Shallow lake facies developed in the LST, TST and RST, whereas semi-deep to deep lake facies developed in the HST. Stable carbon and oxygen isotopes indicate that the Shimengou Lake was semi-closed to closed in the Middle Jurassic. Therefore, the water properties responded strongly to climate changes. According to elemental and mineralogical analyses, a moist climate prevailed, except during the early stages of the TST (stage B1) and HST (stage C1) when there was a semiarid climate. The semiarid climate influenced the water properties and detrital input and was the major controlling factor for the formation of the higher quality oil shales within a saline water environment. In comparison, under the moist climatic condition in the HST, the stable semi-deep to deep-water environment was the major controlling factor for the formation of lower quality oil shales within a fresh water environment.

First occurrence of the Salvador Formation in the Jatobá Basin (Pernambuco, Northeast Brazil): Facies characterization and depositional systems

Fan deltas, constituting proximal depositional systems adjacent to boundary faults, are common features associated with rift basins. The Cretaceous fan delta systems of the Salvador Formation, deposited during the rift phase of the Recôncavo-Tucano-Jatobá Basin, were first reported in the Recôncavo Basin and later discovered in the Tucano Basin. Because of the absence of any outcrops in the Jatobá Basin until now, these alluvial fans were interpreted solely through seismic analysis. We report the first revealed outcrops of the Salvador Formation in that basin and characterize their depositional systems as interlayered with the lacustrine Candeias Formation. Based on facies and architecture, the alluvial system can be subdivided into three associations: (1) proximal fan delta, characterized by meter-scale conglomerate bodies with a predominance of boulders and cobbles with thin sandstone layers; (2) distal fan delta, characterized by sheet-like pebble conglomerate and sandstone layers with flame and load structures; and (3) lacustrine, further subdivided into shallow lake facies reddish shales and mudstones with oolitic limestones and deep lake facies grey to green shales with pyrite. Paleocurrent measurements for the proximal fan association show paleoflow direction varying from SW to SE, which is expected for the rift phase alluvial system. The Recôncavo-Tucano-Jatobá rift system has two conglomeratic units, namely the Salvador and Marizal Formations, the former a syn-rift and the latter a post-rift unit. The absence of sedimentary clasts in the conglomerates, very low maturity, the presence of giant clasts, and a visible relationship between boundary faults in the outcrop, define the syn-rift Salvador Formation characteristics. Based on the facies and paleocurrent analyses, the Salvador Formation deposits in Jatobá Basin were interpreted as a deposition of a debris flow-dominated fan delta, indicating the lacustrine setting represented by the Candeias Formation.

Sequence stratigraphy, sedimentary systems and petroleum plays in a low-accommodation basin: Middle to upper members of the Lower Jurassic Sangonghe Formation, Central Junggar Basin, Northwestern China

The Lower Jurassic Junggar Basin is a low-accommodation basin in northwestern China. Because of low subsidence rates and a warm, wet climate, deposits of the Central subbasin of the Junggar Basin formed from fluvial, deltaic, shallow lake facies. Sequence stratigraphy and sedimentary systems of the Lower Jurassic members of the Sangonghe Formation (J1s) were evaluated by observing cores, interpreting wireline logs and examining seismic profiles. Two third-order sequences were recognized in the strata. The distribution of the sedimentary systems in the systems tracts shows that tectonic movement, paleorelief, paleoclimate and changes in lake level controlled the architecture of individual sequences. During the development of the lowstand systems tract (LST), the intense structural movement of the basin resulted in a significant fall in the water level in the lake, accompanied by rapid accommodation decrease. Braided rivers and their deltaic systems were also developed in the Central Junggar Basin. Sediments carried by braided rivers were deposited on upward slopes of the paleorelief, and braid-delta fronts were deposited on downward slopes. During the transgressive systems tract (TST), the tectonic movement of the basin was quiescent and the climate was warm and humid. Lake levels rose and accommodation increased quickly, shoal lines moved landward, and shore- to shallow-lake deposits, sublacustrine fans and deep-lake facies were deposited in shallow- to deep-lake environments. During the highstand systems tract (HST), the accommodation no longer increased but sediment supply continued, far exceeding accommodation. HST deposits slowly formed in shallow-lake to meandering river delta-front environments. Relatively low rates of structural subsidence and low accommodation resulted in coarse-grained successions that were fining upward. Deposits were controlled by structural movement and paleorelief within the LST to TST deposits in the Central subbasin. Fine- to medium-grained coarsening-upward successions developed during the HST. The sand bodies of braid-delta fronts on the downward slopes of the paleorelief in the LST and the sublacustrine fans in the TST became reservoirs for hydrocarbon accumulation. Petroleum plays have only been found in the Sangonghe Formation (J1s) located on structural ridges that consist of sand bodies comprising these sequences. Favorable conditions for petroleum plays in HST1–LST2 occur where the sand bodies have been fractured by faults and sealed by denudation and pinch-out lines, then overlain by deep lake mudstone in TST2. The favorable condition of the sand bodies within TST2 occurs where isolated sand bodies have been fractured by faults.

Sub-layer Correlation of Quantou IV Formation of the Lower Cretaceous in Haituozi Area of Songliao Basin

Fluvial-flood plain facies are developed at lower-mid Quantou Ⅳ Formation, and delta front - shallow lake facies are developed at the upper formation in Haituozi area of Southern Songliao Basin. Channel sand bodies are good oil and gas reservoirs, but the distribution of sand is not clear, which has become a key factor restricting oil and gas development. No less than 100 wells data of logging, some data of drilling, cores and testing are collected and used in correlation, firstly 5 roughly provenance direction and 5 crosscutting provenance direction sections were selected in the area, with high resolution sequence stratigraphic analysis, Quantou Ⅳ Formation is subdivided into 4 sequences (corresponding to the fifth order cycle sequence, are respectively called cycle A, B, C and D), sequence stratigraphic framework were established. Then the similarity of facies association characteristics in base level change, consistency of reservoir fluid properties, isochronous maximum flooding surface in a certain area, different stages of overlay channels are took full account in the operation of sub-layer correlation. In the end 3 sub-layers are divided from cycle A , 3 sub-layers divided from cycle B, 5 sub-layers from cycle C, and cycles D corresponds to a sub-layer, Quantou Ⅳ Formation is divided into 12 sub-layers, which lays good foundation for the production and development. Key words : High resolution sequence stratigraphy; Sub-layer correlation; Songliao basin; Haituozi area; Quantou Ⅳ Formation

Integrated stratigraphy of the Early Miocene lacustrine deposits of Pag Island (SW Croatia): Palaeovegetation and environmental changes in the Dinaride Lake System

An integrated stratigraphic study of a Neogene lacustrine succession on the Pag Island (Croatia), combining quantitative pollen analysis, magnetostratigraphy, cyclostratigraphy, biostratigraphy and gamma-ray measurements, provides new insights into orbitally controlled variations in palaeo-vegetation and depositional patterns in the Dinaride Lake System. The quantitative palynological record shows a cyclical pattern of vegetation changes that closely corresponds to sedimentological patterns. The intervals with a high abundance of thermophilous and xeric indicators, suggesting a warm and dry climate, generally coincide with intervals of frequent lignite deposition and shallow lake facies. This suggests that both records are dominantly controlled by variations in past climatic conditions and lake level. Our data show two large-scale warming and shallowing-upward cycles, which are interpreted to be forced by the ~ 100 kyr eccentricity cycle of the Earth's orbit. Magnetostratigraphic data of the examined section reveal a long (113 m) reversed polarity interval, followed by a 7 m thick interval of normal polarity at the top. The inferred depositional rate of ~ 0.3 mm/yr, combined with biostratigraphic constraints by mollusks, suggests that the most logical correlation of the reversed interval is to chron C5Cr. This indicates that the Pag succession was deposited between 17.1 and 16.7 Ma and that it corresponds to the Burdigalian Stage of the Early Miocene, and the regional Karpatian Stage of the Central Paratethys. The high relative percentage of thermophilous pollen taxa, Engelhardia and Taxodium-type being the most prominent, generally indicates a subtropical humid climate for the SW Croatian part of the Dinaride Lake System. The observed warming trend is possibly related to the onset of the Miocene Climatic Optimum.