K‐Ar dating of Permian and Tertiary igneous activity in the Southeastern Sydney Basin,New South Wales

The southern part of the Sydney Basin of New South Wales is comprised mainly of Permian and Triassic marine to freshwater clastic sedimentary rocks. Within this sequence there are six latite extrusive units, several medium‐sized monzonite intrusions and a large number of small to medium‐sized basic to intermediate intrusions. Thin basaltic flows were extruded onto the Tertiary topographic surface. All of these rocks are relatively undeformed.

Radiometric (K‐Ar) dating has previously been carried out on Mesozoic and Tertiary intrusions and flows of the southwestern portion of the Sydney Basin. However, relatively few Permian, and no post‐Permian, K‐Ar dates have been published for the southeastern portion of the basin. The present investigation provides nine K‐Ar dates from the latter area.

Four extrusive and intrusive units have been confirmed as Permian in age (238 ± 6; 241 ± 4; 245 ± 6; and 251 ± 5 m.y.). Five post‐Permian (on stratigraphic criteria) intrusions yielded Tertiary ages (26.2 ± 3.0; 47.9 ± 2.5; 49.0 ± 4.0; 49.4 ± 2.0; and 58.8 ± 3.5 m.y.). The Permian ages agree with previously published K‐Ar data from the southeastern Sydney Basin, and the Tertiary ages complement and extend the data from the southwestern portion of the basin. However, no Mesozoic K‐Ar dates were obtained from the southeastern Sydney Basin. The Tertiary intrusions may have been emplaced as a result of rifting between Australia and New Zealand, or between Australia and Antarctica, or both.     

Potential forC Dating of Biogenic Carbonate in Hackberry (Celtis) Endocarps

Hackberry endocarp (Celtissp.) contains significant amounts (up to 70 wt%) of biogenic carbonate that is nearly pure aragonite (CaCO₃). Because of their high mineral content, hackberry endocarps are found abundantly in Tertiary and Quaternary sediments and are very common in many North American archaeological sites. We analyzed the¹⁴C content of different components of modern hackberries including the biogenic carbonate in hackberry endocarps collected at known times over the past century. The¹⁴C content of the endocarp carbonate accurately records the¹⁴C content of the atmosphere.¹⁴C dates of fossil endocarp carbonates compared favorably with dates obtained by other means at archaeological and geological sites ranging in age from the late Pleistocene through the early Holocene. We therefore suggest that hackberry endocarp is a suitable substrate for¹⁴C dating provided that its morphological and mineralogical integrity is preserved.     

南阳凹陷同生断层研究

南阳凹陷是南阳—襄樊新生代盆地的组成部分,不整合叠置在华北地块、秦岭构造带、扬子地块之上,经历了早第三纪沉降、早一晚第三纪间的隆起和晚第三纪—第四纪沉降3期活动。本文根据本区早第三纪形成、活动的生长断层参数的统计、分析了断裂长度、延深、落差间的数学关系。在分析、确定几条主要生长断层性质的基础上,结合区域地质背景,讨论了控制南阳凹陷形成的构造应力场的基本特征。对于进一步研究断层的形成机制和石油勘探工作具有参考价值。     

Review of evidence for late Tertiary shorelines occurring on South Atlantic coasts

Recognition of (late) Tertiary shorelines on continental coasts is becoming increasingly common. It is argued that the elevations of such features are central to their approximate dating and the demonstration of contemporaneity with similar features elsewhere. South Atlantic coasts have not had a long history of investigation, yet there exist many diffuse observations, in both time and space, which are here drawn together into a preliminary synthesis and the case for widespread occurrences of late Tertiary shorelines in the region reviewed. This allows comparison with other areas from which Tertiary shorelines are known, the Atlantic seaboards of the Southeastern United States and Northwest Europe, for example.The coasts of oceanic islands are probably the best places to examine the legacy of late Cenozoic sea-level changes. It is suggested that, since many of the cliffed shores of these islands appear to be the result of a rapid emergence, coastal features predating this event might be preserved on the cliff-tops. Possible late Tertiary shorelines from South Atlantic islands are described, as are those which have been positively dated to this period, in the Eastern Canary Islands, for instance. Sedimentary and morphological indicators of Tertiary high sea-levels are described from Antarctic coasts. South American and African Atlantic continental margins. Evidence from the latter two areas is most suspect, owing to their generally more complex Quaternary tectonic histories. A summary of the evidence for Tertiary shorelines on South Atlantic coasts is tabulated.Methods which have been or could be used to date late Tertiary shorelines are described. Minimum age can be deduced from that of deposits resting on an erosional surface, maximum age from that of the youngest formation across which a surface is cut. More precise age can be estimated where a marine surface is sandwiched between datable non-marine formations or where periods of tectonic activity (responsible for differential surface deformation) can be dated. Elevations of surfaces can be used to estimate ages. Problems in both recognising and dating Tertiary shorelines are discussed. Recognition of their origin is made more difficult by their degraded state and, if they occur within a Quaternary erosional sequence, their antiquity may not be realised.It is suggested that fluctuations in the Antarctic ice sheet during the late Tertiary induced substantial glacio-eustatic changes of sea-level which may have been most marked in adjacent areas. This is considered to be the mechanism through which late Tertiary shorelines in the area were formed yet, considering the paucity of the morphological and sedimentary data, these should not be used as the basis for a eustatic chronology.     

U–Pb isotopic constraints on diachronous metamorphism in the northern Monashee complex, southern Canadian Cordillera

U–Pb isotopic data from the northern Monashee complex, one of the deepest structural exposures in the southern Canadian Cordillera, indicate that the age of metamorphism varies according to structural position in a 6 km thick section. This metamorphism resulted in an unusual sequence in which rocks with the lowest-grade mineral assemblage (kyanite–sillimanite–staurolite–muscovite) are underlain and overlain by higher-grade rocks. Xenotime and monazite U–Pb dates vary progressively from 64 Ma in the structurally highest rocks to 49 Ma in the deepest rocks. Discordant U–Pb ages from Proterozoic and Cretaceous monazite and titanite are used to interpret the thermal significance of the early Tertiary dates. The discordant analyses define linear arrays with lower intercepts that broadly overlap with early Tertiary, and the amount of discordance varies with structural level; it is least in the deeper rocks and greatest in higher rocks. Electron microprobe work showed that the monazite discordance in the deeper rocks resulted from Tertiary mineral overgrowth and recrystallization rather than Pb diffusion. We use previous studies of Pb diffusion and the fact that Proterozoic monazite and titanite suffered only negligible to moderate amounts of diffusive Pb loss to contend that elevated temperatures (c. 600–650 °C are inferred from pelitic mineral assemblages) existed in the deeper rocks for a short duration, perhaps a few million years. The downwards younging 64–49 Ma U–Pb dates are interpreted as closely reflecting xenotime and monazite growth ages rather than cooling ages or substantially reset ages based on the lack of Pb diffusion in monazite and the previously obtained ⁴⁰Ar/³⁹Ar data which suggest that rapid cooling occurred immediately after the U–Pb dates. In addition, growth ages are interpreted as thermal peak ages based on U–Pb dates from coeval kyanite-bearing leucosomes, the consistent nature of the U–Pb dates throughout the study area, and petrographic relationships which suggest that monazite grew before or during development of the syn-metamorphic foliation. These interpretations lead us to conclude that metamorphism was diachronous according to structural level, with higher rocks attaining peak temperatures and cooling rapidly while deeper rocks were heating towards a thermal peak that was attained a few million years later. This thermal scenario requires that higher rocks cannot have been the heat source for the deeper metamorphism, as was previously proposed.     

The Cainozoic geology of the Middle Shoalhaven Plain

The Middle Shoalhaven Plain is a large, tray‐like depression bounded in the west by the Mulwaree fault and in the east by cliffed Permian sediments. The plain is probably Mesozoic in origin and was partially alluviated during the Early to mid‐Eocene. Much of the plain and sediments were covered by basalts during the Late Eocene. This was followed by an episode of deep weathering, which culminated in the formation of widespread bauxitic and lateritic crusts and manganocrete and silcrete during the mid‐Tertiary. A second minor weathering event is recorded during the latest Tertiary to Early Pleistocene. Two new basalt dates are consistent with earlier ones at about 43 Ma. Palaeomagnetism shows bauxites and ferricretes to be mid‐Tertiary.     

中国西天山南缘盆山构造转换解析

在西天山南缘,天山造山带向塔里木盆地北缘的盆山过渡,是以前陆褶皱冲断构造形式向库车一拜城前陆盆地渐变,表现为一系列褶皱冲断组合的构造样式。根据独库公路南段构造变形分析,可组合成６个部分：库尔干一铁力买提达坂根带褶皱系、南天山南缘逆冲断裂带、前陆逆冲推覆构造带、前陆双冲褶皱构造带、前陆隐伏逆冲前缘构造带、沙雅一轮台前缘叠加变形构造带。前陆盆地的发展可以划分为晚二叠一早三叠世、中三叠世一侏罗纪、白垩一     

焉耆盆地侏罗系油气成藏期次分析

着重用油藏地球化学分析方法探讨了焉耆盆地侏罗系油气藏的成藏时间和期次。油源对比表明八道湾组是主力烃源岩层，三叠系烃源岩对八道湾组原油有一定贡献；油气经短距离的侧向运移后，沿断层通道向上进入三工河组和西山窑组。盆地经历了2次生烃，侏罗纪末期为主要生烃期，第三纪晚期为次要生烃期。储层流体包裹体分布特征、均一温度和组分特征、储层自生伊利石测年和油气成熟度分析都显示了焉耆盆地在侏罗纪中晚期的2次成藏作用，即晚侏罗世以八道湾组低成熟油气的生成、运移和聚集为主的第1期成藏事件和侏罗纪末期以成熟油气的生成、运移和聚集为主的第2期成藏事件，受储层流体包裹体和自生伊利石形成机理的控制，第三纪晚期生烃、成藏事件在流体裹体和储层自生伊利石同位素年代学上均没有记录。侏罗纪末期是主要成藏期，第三纪晚期是调整成藏和定型期。     

Isotope Geochemistry of Tertiary Igneous Rocks from the Isle of Skye, N.W. Scotland

New Pb isotope analyses are reported for forty-seven basic,intermediate and acid Tertiary igneous rocks from the Isle ofSkye and adjacent regions of northwest Scotland. New Sr isotopeanalyses and two Rb/Sr isochron dates are also reported forthe acid igneous rocks. These results are combined with publishedSr and Nd isotope data for Tertiary igneous rocks from Skyeand adjacent regions in order to examine the genesis and evolutionof Tertiary magmas in the Isle of Skye. Pb isotope analyses form a linear array on a Pb/Pb isochrondiagram, with a slope yielding an apparent age of 2920 ±70m.y. (2), interpreted as a mixing line between ca. 2900 m.y.-oldcrustal Pb and 60 m.y.-old mantle-derived Pb. Combined isotopicdata support a model of selective crustal Pb, Sr and Nd contaminationof basic and intermediate mantle-derived magmas, without significantmodification of major-element composition. This contaminationprocess is probably due to the breakdown of LIL-element-enrichedaccessory mineral phases, and does not necessarily produce linearmixing lines on isotope ratio plots of different elements. SkyeRedhills epigranites contain a predominant fraction of acidmagma which differentiated from mantle-derived basic precursors,and a subsidiary fraction of upper crustal melt. The proportionof this melt is estimated to rise from less than 10 per centin the older granites to around 30 per cent in the younger. Isotopic and geochemical data are used to draw conclusions aboutthe differentiation histories of the four principal magma typesof Skye: the Fe-rich and Fe-poor members of the Skye Main LavaSeries, Preshal Mhor Basalts and Redhills epigranites.     

Fluid‐induced breakdown of monazite in medium‐grade metasedimentary rocks of the Pontremoli basement (Northern Apennines,Italy)

The last (decompression) stages of the metamorphic evolution can modify monazite microstructure and composition, making it difficult to link monazite dates with pressure and temperature conditions. Monazite and its breakdown products under fluid‐present conditions were studied in micaschist recovered from the cuttings of the Pontremoli1 well, Tuscany. Coronitic microstructures around monazite consist of concentric zones of apatite + Th‐silicate, allanite and epidote. The chemistry and microstructure of the monazite grains, which preserve a wide range of chemical dates ranging from Upper Carboniferous to Tertiary times, suggest that this mineral underwent a fluid‐mediated coupled dissolution–reprecipitation and crystallization processes. Consideration of the chemical zoning (major and selected trace elements) in garnet, its inclusion mineralogy (including xenotime), monazite breakdown products and phase diagram modelling allow the reaction history among accessory minerals to be linked with the reconstructed P–T evolution. The partial dissolution and replacement by rare earth element‐accessory minerals (apatite–allanite–epidote) occurred during a fluid‐present decompression at 510 ± 35 °C. These conditions represent the last stage of a metamorphic history consisting of a thermal metamorphic peak at 575 °C and 7 kbar, followed by the peak pressure stage occurring at 520 °C and 8 kbar. An anticlockwise P–T path or two clockwise P–T loops can fit the above P–T constraints. The former path may be related to a context of late Variscan strike‐slip‐dominated exhumation with minor Tertiary (Alpine‐related) reworking and fluid infiltration, while the latter requires an Oligocene–Miocene fluid‐present tectono‐metamorphic overprint on the Variscan paragenesis.     

灵台风尘堆积中钙质结核的地球化学研究

通过对甘肃灵台风成黄土－古土壤－红粘土序列中钙质结核的野外分布及形态特征观察,并对主元素和微量元素进行化学分析,发现结核中氧化物活动给分和惰性组分含量的比值在剖面中自下而上逐渐变大,反映了结核形成时其上覆土层所经历的淋溶程度逐渐增强;而ＭｇＯ含量校正后的ＭｇＯ／Ｃａｏ比值则逐渐减小,批示结核形成时环境温度逐渐降低。灵台剖面自下而上不同层位结核中Ｓｒ／Ｂａ比值及ＣａＣＯ３含量的变化同氧化物含量及比值     

试论南海新构造运动的时限及其差异性

根据南海地形地貌、地质地球物理剖面资料、重磁场异常、地壳结构特征和岩石圈动力学环境,对南海新构造运动起始时限进行了新的解释。传统的观点是把新近纪作为新构造下限,依此观点,南海地区在古近系、新近系之间应为不整合接触,但在此阶段并没有发生重大变革的构造事件。而符合南海地区准平原化阶段的时代是在中中新世末至晚中新世(N12/N13)之间,在此时段普遍存在区域构造不整合接触和地层缺失、断裂、变形及火山活动等构造变动事件。本文把中中新世末作为南海地区新构造运动开始的时间。通过对南海地区中中新世末至晚中新世之间的构造变动事件的对比研究,可以看出新构造运动在不同地点有时间和强度的差异性、构造运动的差异性、沉积相和沉积建造的差异性等特征。     

Tertiary stratigraphy of Western Australia

This paper is a summary of the present knowledge of the Tertiary stratigraphy of Western Australia. Also included is new information on the Cainozoic of the Carnarvon Basin, a result of petroleum exploration in the area.

Tertiary rocks formed during more than one cycle of deposition in three basins (Eucla, Perth, and Carnarvon), and also as thin units deposited in a single transgression along the south coast. The Tertiary stratigraphy of the Bonaparte Gulf Basin is not well known.

Drilling in the Eucla Basin has encountered up to 400 m of Tertiary in the south central part, with uniform thinning towards the margins. The section begins with a middle‐upper Eocene carbonate unit which represents the dominant event in the Tertiary sedimentation in this basin. More carbonates were deposited in the late Oligocene‐early Miocene and middle Miocene.

Along the south coast, the so‐called Bremer Basin, the Plantagenet Group (up to 100 m) of siltstone, sandstone, spongolite, and minor limestone, was deposited during the late Eocene.

The Perth Basin contains up to 700 m of Tertiary sediment, formed during at least two phases of sedimentation. The upper Paleocene‐lower Eocene Kings Park Formation consists of marine shale, sandstone, and minor limestone, with a thickness of up to 450 m. The Stark Bay Formation (200 m) includes limestone, dolomite, and chert formed during the early and middle Miocene. Events after deposition of the Stark Bay Formation are not well known.

The northern Carnarvon Basin and Northwest Shelf contain by far the most voluminous Tertiary sediment known from Western Australia: 3500 m is known from BOCAL's Scott Reef No. 1. A more usual maximum thickness is 2500 m. Most sediments were laid down in four episodes, separated by unconformities: late Paleocene‐early Eocene; middle‐late Eocene; late Oligocene‐middle Miocene; and late Miocene to Recent.

The Paleocene‐early Eocene cycle consists of about 100–200 m (up to 450 m in the north) of carbonate, shale, and marl of the Cardabia Group containing rich faunas of planktonic foraminifera.

The middle‐late Eocene sediments include diverse rock types. Marine and nonmarine sandstone formed in the Merlinleigh Trough. At the same time, the Giralia Calcarenite (fauna dominated by the large foraminifer Discocyclina) and unnamed, deeper water shale, marl, and carbonate (with rich planktonic foraminiferal faunas) formed in the ocean outside the embayment. Thickness is usually of the order of 100–200 m.

The main cycle of sedimentation is the late Oligocene‐middle Miocene, during which time the Cape Range Group of carbonates formed. This contains dominantly large foraminiferal faunas, of a wide variety of shallow‐water microfacies, but recent oil exploration farther offshore has recovered outer continental shelf facies with abundant planktonic foraminifera. A minor disconformity representing N7 and perhaps parts of N6 and N8 is now thought to be widespread within the Cape Range Group. The last part of this cycle resulted in sedimentation mainly of coarse calcareous marine sandstone (unnamed), and, in the Cape Range area, of the sandstone and calcareous conglomerate of the Pilgramunna Formation. Maximum thickness encountered in WAPET wells is 900 m.

After an unconformity representing almost all the late Miocene, sedimentation began again, forming an upper Miocene‐Recent carbonate unit which includes some excellent planktonic faunas. Thickness is up to 1100 m.

Thin marine sediments of the White Mountain Formation outcrop in the Bonaparte Gulf Basin. They contain some foraminifera and a Miocene age has been suggested.     

Geometry and kinematics of the Mosha Fault, south central Alborz Range, Iran: An example of basement involved thrusting

Field investigation of the western part of the Mosha Fault in several structural sections in the south central Alborz Range showed that the fault has a high angle of dip to the north, and emplaces Precambrian to Cenozoic rocks over the Eocene Karaj Formation. Study of the kinematics of the Mosha Fault in this area, based on S–C fabric and microstructures, demonstrates that it is a deep-seated semi-ductile thrust. Strain analysis on rock samples from different sections across the Mosha Fault shows a flattening pattern of deformation in which the long axis of the strain ellipsoid is aligned in the fault shear sense. The Mosha Fault is associated with a large hanging-wall anticline, cored by Precambrian rocks, and series of footwall synclines, formed of late Tertiary rocks. This geometry, together with several low angle short-cut thrusts in the fault footwall, implies that the Mosha Fault is an inverted normal fault which has been reactivated since the late Tertiary. In the study area, the reverse fault mechanism was associated with the rapid uplift and igneous activity in the central Alborz Range during the late Tertiary, unlike in the eastern portion of the fault, where the fault kinematics was replaced by a strike-slip mechanism in the Late Miocene.     

Unusual biomarker maturation ratio changes through the oil window, a consequence of varied thermal history

Saturated and aromatic biomarker ratios continue to change systematically through the oil window and into the gas-condensate window to high vitrinite reflectances (R_o = 1.16%) in mature marine and lacustrine Mesozoic clastic samples from a South African basin. Two of the ratios reverse above R_o = 0.9%. These unusual maturation effects result from isolated periods of high rates of maturation increase. The basin cooled regionally after the break-up of Gondwana but high heating rates prevailed during the late Cretaceous-early Tertiary, as Africa moved across a hotspot, and again in the late Tertiary as a result of a possible hotspot and hydrothermal event.     

K-Ar ages of basic rocks in the Patia Valley, southwest Colombia

The Patia Valley situated between the Western and Central Cordilleras of the southwest Colombian Andes contains two areas in which Mesozoic basic and ultrabasic rocks crop out in abundance. Late Cretaceous Diabase Group pillow basalts which make up much of the Western Cordillera are at least 81 ± 5 Ma in the E1 Tambo-E1 Peñol area. 105-97 Ma hornblende and whole-rock dates from the ophiolitic Los Azules complex indicate an Albian age of formation, although many dates are lower (65-62 Ma) owing the low-grade ocean-floor metamorphism. The metamorphic age distribution here supports an end of Cretaceous emplacement for the complex rather than the Early-Mid Cretaceous emplacement suggested for North Colombian ophiolites similarly aligned along the Romeral fault system. Tertiary dacites intruding the Low Azules complex are 36-15 Ma.     

Geology and tectonic development of the continental margin north of Alaska

The continental margin north of Alaska, as interpreted from seismic reflection profiles, is of the Atlantic type and consists of three sectors of contrasting structure and stratigraphy. The Chukchi sector, on the west, is characterized by the deep late Mesozoic and Tertiary North Chukchi basin and the Chukchi Continental Borderland. The Barrow sector of central northern Alaska is characterized by the Barrow arch and a moderately thick continental terrace build of Albian to Tertiary clastic sediment. The terrace sedimentary prism is underlain by lower Paleozoic metasedimentary rocks. The Barter Island sector of northeastern Alaska and Yukon Territory is inferred to contain a very thick prism of Jurassic, Cretaceous and Tertiary marine and nonmarine clastic sediment. Its structure is dominated by a local deep Tertiary depocenter and two regional structural arches.We postulate that the distinguishing characteristics of the three sectors are inherited from the configuration of the rift that separated arctic Alaska from the Canadian Arctic Archipelago relative to old pre-rift highlands, which were clastic sediment sources. Where the rift lay relatively close to northern Alaska, in the Chukchi and Barter Island sectors, and locally separated Alaska from the old source terranes, thick late Mesozoic and Tertiary sedimentary prisms extend farther south beneath the continental shelf than in the intervening Barrow sector. The boundary between the Chukchi and Barrow sectors is relatively well defined by geophysical data, but the boundary between the Barrow and Barter Island sectors can only be inferred from the distribution and thickness of Jurassic and Cretaceous sedimentary rocks. These boundaries may be extensions of oceanic fracture zones related to the rifting that is postulated to have opened the Canada Basin, probably beginning during the Early Jurassic.     

Chronology of late wisconsinan glaciation in middle North America

We propose a chronology of late Wisconsinan glacial fluctuations in middle North America, from Alberta to Wisconsin, based on radiocarbon dates derived solely from wood. Previous chronologies of the southwestern margin of the North American Continental Ice Sheet have depended to a considerable degree on radiocarbon dates from fine-grained organic sediment. This material is commonly contaminated with older carbon, resulting in chronologic confusion. By using only dates from wood, much of the confusion disappears. However, because of the scarcity of wood dates, only four of the sixteen identified fluctuations are accurately dated: an advance into Iowa about 14,000 to 13,500 BP, an advance into South Dakota and Iowa about 12,300 BP, an advance into the Lake Michigan basin about 11,700 BP, and an advance into the Lake Superior basin about 9900 BP. In addition, the beginning of late Wisconsinan glaciation, before 20,000 BP, is fairly well documented. None of the fluctuations in the western part of the region are accurately dated.     

兰州地区新近纪地层的沉积相与古环境记录

兰州地区位于黄土和青藏高原的过渡带,其第三纪地层对研究风尘沉积发育和青藏高原隆升都有着特殊的意义。本研究以0.25 m为间距对厚度210 m的兰州皋兰山剖面的新近纪地层采集样品901个,在实验室对试验样品进行前处理后对其进行了粒度、磁化率和色度测试。用粒度分布函数的方法分离了沉积物的各成因组分,确定了风成组分和水成组分在全剖面沉积物中所占的百分比。结合色度和磁化率的实验结果分析表明,皋兰山剖面地层以风尘沉积为主,其间夹有河流相沉积的约15层砂岩。古环境的恢复表明,兰州地区从至少约7 Ma开始,沉积地层经历了由河湖相向风尘沉积转变,气候干旱化开始,与黄土高原风尘序列堆积底界8～7 Ma基本一致。6～5.2 Ma构造稳定,是比较开阔的平原环境,并且气候条件比较湿热;5.2～3.5 Ma间构造波动比较频繁,形成了间隔性的河流相砂岩沉积,而在气候表现为干冷;自3.5 Ma开始,兰州地区发生相对构造沉陷,五泉砾岩层的发育是对青藏运动A幕的具体响应。     

Experiment on imaging and visualising for assessing late-tertiary microstructural evidences of depositional changes in Gajalia fold,south Tripura

The present work concentrates on microstructure imaging for visualising the changes of depositional environment during Tertiary period. For that purpose Tipam layers of Gajalia fold area in southern Tripura was selected which was deposited during late Tertiary period under marine-coastal environment. Thin sections of eleven selected samples of the study area were prepared in the laboratory for microstructure analysis. For visualising the crystalline particles or quartz brightness and contrast of the image was increased up to maximum level. Surface conditions of the samples were analysed within RGB combination. The grain size and shapes of the eleven samples tested prove that the depositional environment remained very dynamic through Tertiary period in the study area. The microstructure and surface conditions also strongly support this view.