Lower Cretaceous Strata Research Articles

Vitrinite reflectance as an indicator of thermal alteration within paleozoic and mesozoic sediments from the Phillips petroleum company asm‐1x well, Arafura Sea

Abstract Vitrinite reflectance of Phillips Petroleum Company's ASM‐1X indicates that the strata penetrated by this well have experienced a moderate amount of thermal alteration. Samples dated by palynology as Late Permian, Early Triassic and Early Cretaceous have reflectance values which place them at the initial stage of thermal maturity for peak generation of liquid hydrocarbons. Studies of relative abundance of amorphous kerogen indicate a lack of potential source material for liquid hydrocarbons within the studied interval of the ASM‐1X. Palynology data indicate that a major unconformity has resulted in marine Lower Cretaceous strata being directly superjacent to non‐marine Lower Triassic and Upper Permian strata. A possible location of liquid hydrocarbon source material within Lower Triassic and Upper Permian strata could be in time equivalent marine facies.

Heavy Oil Sand In.-Situ Pilot Plants In Alberta (Past And Present)

Abstract This paper will review the history of in situ pilot plant efforts towards the recovery of bitumen from the major oil sand deposits of Alberta. The review will be based on published information and will describe the location of the plants, the manner of operation, the estimated costs involved and the technical area under investigation. The currently operating pilot plants and future plans for new in situ pilots will also be described. INTRODUCTION This paper will present a survey of the planned, current and completed in situ pilot plant operations in the Alberta Oil Sands. The aim of the review is to provide an overview of the current field projects and to provide background concerning completed in situ pilot plant programs. Before beginning a consideration of the individual plants it is necessary to set the stage for the review by looking at some of the problems and formation properties which are encountered in the Alberta on Sands. Note that the term bitumen, tar and heavy oil are used interchangeably in this paper to describe hydrocarbon material with gravity less than 12 °API. The oil sands of Alberta, as shown in Figure 1, are located in four major deposits which cover an area of about 10.8 million acres in the northern half of the province. The total in place reserves are estimated to be 950 billion barrels(1) of which, 74 billion barrels or 8% of the total are covered by less than 150 feet of overburden and are considered suitable for economic surface mining. The surface mineable reserves are all located within the Athabasca deposit as indicated by the heavily shaded area in Figure 1. The amount of in place bitumen which has more than 500 feet of overburden and must be recovered by in situ methods is 10 times the surface mineable reserves; 741 billion barrels or 78% of the deposit. The remainder, 135 billion barrels are overlain by 150–500 ft. of overburden and it is uncertain at this time whether the heavy oil in these sands will be recovered by some form of mining or by novel in situ recovery methods. The consideration of the depth of the deposits points out the need for development of in situ recovery techniques in order to tap the majority of the reserves in the Alberta Oil Sands. RESERVOIR PROPERTIES The Alberta Oil Sand Reserves are situated in the Mannville Group of the Lower Cretaceous strata. All the oil sand deposits are quite heterogeneous, both laterally and vertically, with wide variations in oil, water and gaseous content. Some of the average oil sand formation properties are shown in Table 1. The Athabasca deposit has the largest in place reserves; 626 billion barrels or 66% of the total. The Cold Lake deposit is next largest with 164 billion barrels followed by the Wabasca and Peace River deposits. The Athabasca deposit is the only one inwhich the oil sand outcrops at the surface.

Palynofloral evidence for terrestrial Middle Jurassic in the Moose River Basin, Ontario

Miospore assemblages from a drill hole in the western Moose River Basin comprise 26 species, coniferalean pollen being numerically dominant. Some species are common to putative Middle Jurassic horizons in the western Canadian plains, and comparisons can also be made with the British and French Middle Jurassic. A large hiatus exists between the terrestrial Middle Jurassic sediments and overlying terrestrial Albian (Lower Cretaceous) strata comprising the Mattagami Formation, and may parallel a similar hiatus in southeast Saskatchewan.

EXPLORATION IN THE ARAFURA SEA

Geophysical exploration and drilling have delineated four major geological elements in the Arafura Sea. A stable block of relatively thin, seaward dipping Mesozoic and Cenozoic strata is separated by a Mesozoic structural and stratigraphic hinge zone from a mobile block of much thicker sediments. Gentle folding disturbs the Lower Cretaceous strata in the mobile block and along the hinge zone, but has little effect on the overlying Tertiary sediments. A strongly folded and faulted pre-Mesozoic graben is the dominant structural element in the stable block.

Deltaic Sedimentation in Athabasca Tar Sands

The Athabasca tar sands of northern Alberta underlie an area greater than 26,000 sq km and contain more than 700 billion bbl of heavy oil. Excellent outcrops of the oil-impregnated Lower Cretaceous strata (McMurray and Clearwater Formations) are present in the valley of the Athabasca River and its tributaries near Fort McMurray. The middle and upper members of the reservoir consist of many small deltas of limited thickness (less than 30 m) built by rivers flowing northward into a lake or lagoon. The water occupied an elongated depression formed by extensive salt removal from evaporite beds beneath the Devonian limestone which underlies the tar sands. Lithofacies associated with the changing environments of deposition during the infilling of this depression include, succes ively, fluvial sand; delta-front sand and silt; deltaic-platform sand, silt, and clay; and nearshore marine sand. The distribution of oil within the tar-sands reservoir is strictly controlled by the original porosity and permeability of the sediments. Thus, the maximum amount of oil (18-20 percent by weight) is present in well-sorted, clean sands that are most commonly of fluvial origin. No oil is present in the poorly sorted, argillaceous parts of the nearshore marine sands, or in the silt beds within the deltaic complex.

Sedimentation and Thrusting of Late Mesozoic Rocks in the Coast Ranges near Clear Lake, California

South and southeast of Clear Lake, California, approximately 35,000 ft of clastic sedimentary strata of the Great Valley sequence ranging in age from Late Jurassic to Late Cretaceous crop out in irregular belts trending from northwest to southeast. Together with overthrust lower Tertiary beds, these rocks form a thrust complex that rests structurally upon the Franciscan assemblage of late Mesozoic age along the Soda Creek thrust and is overlain unconformably by late Cenozoic strata. A number of subsidiary thrusts, that are discordant to bedding, break the Great Valley sequence into at least three and possibly more than four successive thrust plates or slices. In all exposed cases, younger strata overlie older strata along the thrusts. The principal structurally intact stratigraphic components of the thrust complex are: A conformable Tithonian to Valanginian succession, 6900 ft, dominantly mudstone with 1600 ft of lithic sandstone and conglomerate in the upper part. Lower Cretaceous strata, 4500 ft, in part Aptian, dominantly thin-bedded quartzose sandstone and mterbedded mudstone. Three structurally isolated “mid”-Cretaceous successions, two of massive sandstone and one of mudstone, total of 5700 ft exposed. A conformable Upper Cretaceoussuccession, 17,500 ft, in large part Campanian, composed of five mappable units including massive sandstone (3700 ft), siltstonc (3600 ft), massive sandstone (4000 ft), mudstone (1000ft), and alternating sandstone and mudstone (5200 ft) in ascending order. A conformablemarine Paleocene and Eocene succession (5500 ft). The lithologic characteristics, petrologic variations, and paleocurrent indicators oi the strata in the Great Valley sequence near Clear Lake are comparable to those of correlative parts of the Great Valley sequence along the western side of the Sacramento Valley. Emplacement of the Great Valley sequence and the lower Tertiary beds above the Franciscan assemblage by regional thrusting was probably complete by Oligocene time from evidence elsewhere in the Northern Coast Ranges. The thrusts themselves and the strata of the thrust complex were later folded and cut by younger normal and reverse faults during Cenozoic deformations.

Nature of Cretaceous Sedimentation in Western Desert, Egypt

The Cretaceous System in the Western Desert of Egypt has several sedimentary and tectonic features that are not observed in the underlying formations. Throughout Cretaceous time, changes in the tectonic pattern, depositional environment, and sediment types indicate different magnitudes of tectonic instability. From the available surface and subsurface data, 22 stratigraphic maps were constructed to show thickness variations, facies changes, and paleogeology of Early Cretaceous, Cenomanian, Turonian, and Senonian times. The Lower Cretaceous sequence is a thick fluviatile-marine to marine sequence of carbonaceous sandstone with intercalations of carbonaceous shale and a small amount of limestone. Two maximum thickness trends are present. Maximum thickness is about 3,100 m. A deeply weathered, high Basement Complex massif east of the desert, extended to the present Nile Valley. The configuration of this massif affected the nature and type of sediments that were deposited. As the sea transgressed southward, the sites of maximum Cretaceous deposition were changed. During Cenomanian time, the principal basin was at the center of the Western Desert; maximum thickness is about 900 m. The Cenomanian is marine and continental, and consists of sandstone and shale in the south, and limestone both at the rim of the basin and in the north. A partly restricted environment probably dominated; in the Baharia Oasis area, a prodelta environment is inferred to have existed. At least two stages of tectonic uplift took place in some localities (e.g., the Baharia Oasis area) during the Cenomanian. At the end of Cenomanian time, the basin was broken up, and Turonian sediments are present mainly in two basins. Open-marine conditions prevailed in both basins where a maximum thickness of 800 m was deposited. The section contains abundant carbonate, which is extensive laterally and vertically. Conspicuous uplift took place in some areas during and at the end of the Turonian. During Senonian time, the Western Desert area was the site of another open-marine transgression. A semi-restricted environment probably existed in the south, where the maximum thickness was deposited. Lithologically, the Senonian shows normal facies changes; sandstone and claystone are present on the south and limestone on the north. Subaerial and submarine highs were present, particularly near the middle of the Western Desert area. The high Basement Complex massif that existed during the Early Cretaceous was reduced in size during the Cenomanian-Senonian period. After Senonian time, the massif was not exposed, except for some islands. The Cretaceous rocks are good petroleum reservoirs. Cenomanian and Lower Cretaceous strata possibly were favorable source rocks. Economic deposits of oolitic iron ore and phosphorite accumulated in semirestricted depositional environments near the Senonian shoreline.

The Fossil Fish Lepidotes in the Paluxy Formation, North-Central Texas

Study and reconstruction of disarticulated bones of a fish recovered from the Paluxy Formation of the Trinity Group (Albian) in Wise County reveal that the characters shown in the dermal elements of the skull, dentition and squamation agree with typical characteristics of the semionotid fish genus Lepidotes. Because of the incomplete nature of the specimen it is referred to Lepidotes sp. Superficially it bears a closer resemblance to L. mantelli Agassiz of Lower Cretaceous strata than to any other species but it also has a surprising number of characters in common with Upper Jurassic species. The nature of its dentition suggests that it fed on mollusks in a freshwater environment.

Burial Metamorphism of the Late Mesozoic Great Valley Sequence, Cache Creek, California

In sandstones of the Great Valley Sequence of Mesozoic age at Cache Creek, post-depositional albitization of plagioclase and chloritization of biotite are widespread in noncalcareous rocks, but uncommon in rocks with calcareous cement. The degree of alteration increases systematically with age and inferred depth of burial in Upper Cretaceous strata, and is uniformly great in Lower Cretaceous strata that were buried from 20,000 to 30,000 feet. Laumontite is characteristic of thoroughly altered Lower Cretaceous rocks. Other metamorphic assemblages may be widespread at higher and lower horizons.

Geology of Parras Basin and Adjacent Areas of Northeastern Mexico

The Parras basin, in southern Coahuila and western Nuevo Leon, Mexico, contains 4,500-6,000 meters of Upper Cretaceous and lower Tertiary terrigenous sedimentary rocks. Approximately 1,500-2,100 meters of Lower Cretaceous carbonate rocks and 2,000-3,000 meters of Triassic and (or) Jurassic evaporites, carbonates, and terrigenous rocks flank parts of the basin and underlie large areas within the basin. The Triassic and (or) Jurassic sedimentary rocks exhibit complex facies relations. Lower Cretaceous carbonate rocks are remarkably uniform in large areas of northeastern Mexico. Most of the Upper Cretaceous and lower Tertiary sediments were deposited in a boot-shaped, shallow, subsiding basin between the present-day Sierra Madre Oriental and Coahuila platform. The Upper Cretaceous-lower Tertiary Difunta Group displays intertonguing relations between two distinct lithic types: red, non-marine to brackish-water sandstone and shale alternate with gray to black, brackish-water to marine, calcareous sandstone and shale. Regionally the red strata pinch out or change facies toward the north and east in the basin where marine deposition was continuous from Late Cretaceous to early Tertiary time. Some redbeds change facies down depositional dip into gray marine strata. Red strata also have been discovered in the Upper Cretaceous Parras Shale, which normally is gray to black, calcareous shale, 1,200-1,500 meters thick. During Paleocene or Eocene time, the sediments of the Parras basin were deformed contemporaneously with the adjacent Sierra Madre Oriental structural belt. Deformational intensity in the Upper Jurassic and Lower Cretaceous carbonate rocks of the nearby Sierra Madre appears to be related to the distribution and thickness of the Minas Viejas (Triassic and [or] Jurassic) evaporites. The type and degree of deformation within the Parras basin are not uniform as indicated by three factors. (1) Overturned folds and imbricate thrusts, which probably do not extend below the Parras Shale, characterize the constricted western part of the basin; (2) broad, elongate, open folds in the southeastern part extend downward to folds in Lower Cretaceous strata; and (3) broad, open, domal folds in the n rtheast are related to Lower Cretaceous uplifts on the surface and at depth.

Lower Cretaceous of Wyoming and Southern Rockies: ABSTRACT

Lower Cretaceous strata (essentially the Dakota Group) of Wyoming and the Southern Rockies are of considerable economic importance. To date recoverable reserves of about 450 million bbl of oil and 1½ trillion cu ft of gas have been discovered in these rocks. Lower Cretaceous sediments were deposited in the incipient Rocky Mountain geosyncline which seemingly began to subside in this region in Aptian time. The first sediments to be laid down were inland floodplain conglomerate, sandstone, and variegated mudstone (Cloverly, Lakota, Lytle, lower Cedar Mountain, etc.) transported into this depression by river systems from the Sioux uplift on the east and from the Mesocordilleran geanticline on the west. As the transgressing arboreal sea entered this part of the trough, and ultimately joined the southern sea, environmental relations became more complex. Marine shale and siltstone (Skull Creek, lower Thermopolis, and Kiowa) formed in the deeper part of the trough occupied by the sea and graded landward (eastward and westward) into sandstone, shale, and coal of the transitional littoral-marine-lagoonal, paludal, and deltaic environments (Fall River, upper Cedar Mountain, Plainview, upper Cheyenne, etc.). These, in turn, graded laterally into sandstone and variegated mudstone of the now restricted floodplain environment. Toward the end of Early Cretaceous time, a low arch rose in southern Kansas and southern Colorado, separating the trough into two parts. However, continuing subsidence allowed the sea to spread greatly both east and west. Floodplain deposits (now composed of sandstone and mudstone) continued to accumulate between the source areas and the arboreal sea and interfinger seaward with shale and sandstone of the transitional environments (Omadi, Dakota, Naturita, etc.). These in turn interfinger with the marine upper Thermopolis and Mowry Shales. Tongues of these formations (Newcastle, Muddy, J, etc.) project seaward into the marine shale and probably represent deltaic wedges formed during minor regressions of the sea. Petroleum has been produced from nearly all the units mentioned, representing deposits of marine, littoral, deltaic, paludal, lagoonal, and floodplain environments. Most production has come from Newcastle, J, and Muddy sandstones which probably are deltaic and littoral marine complexes. End_of_Article - Last_Page 1907------------

Stratigraphy and Structure of Parras Basin and Adjacent Areas of Northeastern Mexico: ABSTRACT

The Parras basin, in southern Coahuila and western Nuevo Leon, contains 15,000-20,000 feet of Upper Cretaceous and lower Tertiary terrigenous clastic sediments. From 5,000-7,000 feet of Lower Cretaceous carbonate rocks and 6,000-10,000 feet of Triassic and (or) Jurassic evaporites, carbonate, and terrigenous clastic rocks flank parts of the basin and underlie large areas within the basin. The Triassic and (or) Jurassic sedimentary rocks exhibit complex facies relations. Lower Cretaceous carbonate rocks are remarkably uniform over large areas of northeastern Mexico. Most of the Upper Cretaceous and lower Tertiary calcareous-arenaceous-argillaceous sediments were deposited in a boot-shaped, shallow, subsiding basin between the present-day Sierra Madre Oriental and the Coahu la Platform. The Upper Cretaceous-lower Tertiary Difunta Group displays intertonguing relations between two distinct lithic types; red, non-marine, arenaceous-argillaceous End_Page 639------------------------------ strata alternate with gray to black, brackish, calcareous-arenaceous-argillaceous strata. The red formations pinch out or change facies toward the north and east in the basin. Marine deposition was continuous from Late Cretaceous to early Tertiary in the eastern part of the basin. A few redbeds grade down depositional dip into gray, marine strata. Red strata have been discovered in the Upper Cretaceous Parras Shale, which normally is a gray to black, calcareous shale, 4,000-5,000 feet thick. During Paleocene or Eocene time, the sediments of the Parras basin were deformed contemporaneously with the adjacent Sierra Madre Oriental. Deformational intensity in the Lower Cretaceous carbonate rocks of the Sierra Madre appears related to the distribution and thickness of the Minas Viejas (Jurassic?) evaporites. The type and degree of deformation in the Upper Cretaceous Parras basin is not uniform as indicated by the following: (1) overturned folds and imbricate thrusts, which probably do not extend below the Parras Shale, characterize the constricted western part of the basin; (2) broad, elongate, open folds in the southeastern part extend downward to folds in Lower Cretaceous strata; and (3) broad, open, domal folds in the northeast are related to Lower Cretaceous uplifts on the surface and at depth. End_of_Article - Last_Page 640------------

ASPECTS OF THE STRUCTURE OF THE SALT DOMES IN THE CASPIAN SYNCLINE

Lithologic and paleontologic studies of cores, in conjunction with logs, from wells on eight domes in South Emba show that marine Lower Cretaceous and Upper Jurassic strata are mostly constant in thickness and facies. There are up to 12 unconformities that can be traced in all eight domes and these point to regional tectonic movements. All domes show similar development, grew discontinuously, and uplifting halted temporarily on several occasions during which strata consistant in facies and thickness were deposited. Salt cores show little dislocation, outlines of the stocks are fairly smooth, and salt seldom breaks through the overlying strata. Salt is found at depths of about 2 km and recent seismic studies show the base of the salt at depths of 5 km to 9 km and show that the flanks are steep even at depth. The domes were formed in two stages: Paleozoic (Upper Permian) and Mesozoic Cenozoic In the first stage they were formed as in other regions; became columnar (even mushroom-shaped), broke through overl...

Esquisse stratigraphique du Jurassique superieur et du Cretace inferieur du chainon du Mail-Arrouy (Basses-Pyrenees)

Abstract A relatively complete section of upper Jurassic and lower Cretaceous strata occurs on the north flank of the Mail-Arrouy mountain in the Basses-Pyrenees. Apparently only basal lower Cretaceous is lacking or perhaps incompletely represented. Study of the microfacies in these formations facilitates correlation with other outcrops in southern and western Aquitaine.

Tectonics of Central Montana: ABSTRACT

Central Montana has been tectonically active at least since pre-Devonian time. This activity has been in seven stages: (1) pre-Cambrian to post-Devonian uplift and erosion, (2) early Mississippian Big Snowy downwarp, (3) Heath uplift, (4) pre-Jurassic epeirogeny, (5) late Laramide orogeny, (6) late Eocene or post-Eocene igneous intrusions, (7) pre-Pleistocene epeirogeny. The late Laramide orogeny and late Eocene or post-Eocene igneous intrusions account for the asymmetrical (Big Snowy Mountains) tectonic features and the laccolithic domes (Judith Mountains) visible to-day. Accumulation of oil in central Montana is found in both structural (Cat Creek field) and a combination of stratigraphic and structural traps (Northwest Sumatra field). Geologically the oldest producing ormation is the Mississippian Kibbey sand (Ragged Point field) and the youngest is the Lower Cretaceous First Cat Creek sand (Cat Creek field). The conclusion can be made that central Montana tectonics were not restricted to Laramide time. Oil has been found in lenticular or isolated sandstones but very little has been found in the widespread sandstones of the Jurassic and Lower Cretaceous. One may speculate that oil which initially accumulated in these sands migrated from the central Montana area or its margins prior to the late Laramide orogeny. The subsequent cropping out of the Jurassic and Lower Cretaceous strata during late Laramide deformation and erosion caused an increase in formation hydrostatic pressures making it more difficult for the oil to migrate back into central Montana and into the present structures. End_of_Article - Last_Page 788------------

Developments in Canada in 1947

Developments in Canada in 1947

UPPER LIMIT OF THE JURASSIC SYSTEM

Research Article| September 01, 1947 UPPER LIMIT OF THE JURASSIC SYSTEM ARMANDO F LEANZA ARMANDO F LEANZA DIRECTIÓN GENERAL DE MINAS Y GEOLOGÍA, PERU 562, BUENOS AIRES, REPÚBLICA ARGENTINA. Search for other works by this author on: GSW Google Scholar GSA Bulletin (1947) 58 (9): 833–842. https://doi.org/10.1130/0016-7606(1947)58[833:ULOTJS]2.0.CO;2 Article history received: 09 Oct 1946 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation ARMANDO F LEANZA; UPPER LIMIT OF THE JURASSIC SYSTEM. GSA Bulletin 1947;; 58 (9): 833–842. doi: https://doi.org/10.1130/0016-7606(1947)58[833:ULOTJS]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract This paper deals with the zonal paleontological sequence of the uppermost Jurassic and lower Cretaceous strata on the strength of the Argentine ammonite fauna. Some misleading interpretations regarding the so-called Spiliceras damesi and Parodontoceras callistoides zones are pointed out, and some significant species actually found in them are discussed. Thus evidence is provided toward clarification of several interpretations formerly advanced about the Upper Jurassic boundary as a whole. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A Group of Fossil Plants 1

THE publication of Mr. Wieland's first volume in 1906 was an event of great importance which had a wide influence on botanical research. The author gave an account of the floral and vegetative morphology of several species of Cycadeoidea, a genus represented in Upper jrassic and Lower Cretaceous strata in many parts of the world, but nowhere on so large a scale as in the United States, where hundreds of well-preserved trunks have been found. Though agreeing generally in habit and in most anatomical features with recent Cycads, Cycadeoidea is characterised by reproductive shoots of a type far removed from that of the existing members of the Cycadacere. The work accomplished by European investigators since Wielands first volume was published is summarised in the present volume, which also contains many new facts and amplifies the earlier descriptions; it also includes some account of the authors Mexican expedition in 1909-10, which yielded a rich harvest of Liassic Cycadean fossils. Incident ally Mr. Wieland emphasises the importance of personal observation in the field, and gives salutary advice to many of us who have neglected this part of a palæcobotanist's duties. He directs attention to the short sighted policy of some museum authorities in refusing to allow their specimens to be disfigured by the lapidarys wheel.

On some Recent Borings through the Lower Cretaceous Strata in East Lincolnshire

The information on which this communication is based has been in my possession since 1889, but pressure of other work had prevented me from preparing it for publication until the present time. The results of the borings which are here described are important, because they give information concerning the geological structure of the platform which underlies the Glacial Drift on the eastern side of the southern part of the Lincolnshire Wolds. We learn from them that the outcrop of the Lower Cretaceous sands and clays extends much farther northward beneath the Drift on this side of the Wolds than there was any reason to suspect at the time when I mapped the area for the Geological Survey. §1. The Boring at Willoughby (1887). Willoughby is a village between the towns of Burgh and Alford, and the site of the boring ,is at the station on the East Lincolnshire Railway, which is the junction for the new branch-line to Sutton. The boring was made for the Railway Company in 1887, and a good supply of water was procured at a depth of 245 feet. For information regarding the beds passed through I am indebted, in the first place, to Mr. H. Cheetham, the engineer of the railway ; but the description of the strata furnished by him being only a well-sinker's account, and not sufficiently accurate to enable me to identify the strata, I wrote to my friend, Mr. Meaburn Staniland, F.G.S., asking if he could take an opportunity of looking the

IV.—Lower Greensand and Purbecks in the Vale of Wardour, Wilts

In the Geological Magazine for July last the Rev. W. Andrews and Mr. Jukes-Browne gave an account of Lower Cretaceous strata in the Vale of Wardour. I can bear testimony to the correctness of this statement. Many years ago, when geologizing in the vale chiefly among the Purbecks, I found many portions of ironstone and hard ferruginous sandstone, in the fields and by the roadside both at Dinton, Teffont and especially at Chilmark, containing casts of Cyrena, Turritella, and a part of a dermal scute of a Saurian, which I believe belong to the Lower Greensand, but I never saw it in situ, and it seems to have been greatly denuded.