Pleistocene Bedrock Research Articles

Prediction of clinical effects of some anxiolytic and hypnotic drugs by averaged photopalberal reflex : M. Tanaka, H. Isozaki and K. Inanaga (Kurume, Japan)

Paleoclimate changes are reconstructed from Late Miocene-earliest Pleistocene deep-water sediments of the Solo River section, using fluctuations in planktonic foraminiferal faunas, water depth and clastic influx. Intervals with common cold-water planktonics (Globigerina bulloides, Neogloboquadrina cf. pachyderma) are thought to reflect periods of increased upwelling, triggered by Antarctic glaciations.Correlations with well Bodjonegoro-1 (Java), DSDP Site 62-1 and Lamont Core RC 12–66 (Equatorial Pacific) using planktonic foraminiferal datum levels and paleoclimate trends suggest non-synchroneity of several commonly used datums, probably due to differences in species concepts. It also allowed dating of the climate changes with regard to the magnetostratigraphic and numerical time scales.For correlations between different faunal provinces global climate changes are an extremely useful tool, probably superior to any single faunal datum. Using this, with other evidence, the following correlations could be obtained between the five “climatostratigraphic” zones in the Solo River section and the Mediterranean and New Zealand stages (from bottom to top): 1.Zone I, samples SR 63–SR 53, cool, older than 6.0 m.y. – ±5.8 m.y., magnetostratigraphic Epoch 6 (and older?) — basal Epoch 5, planktonic zone (Upper N16?-) N17, Mediterranean stages (upper?) Tortonian—Early Messinian, New Zealand Stages Tongaporutuan—Early Kapitean, Late Miocene.2.Zone II, SR 52–SR 35, moderately warm with fluctuations, ± 5.8 m.y.–5.0 m.y., Epoch—lowermost Gilbert, upper N17 (−N18?), Late Messinian (evaporite phase), Late Kapitean, Late Miocene.3.Zone III, SR 34–SR 33, cool, 5.0–4.8 m.y., within Lower Gilbert, (N18?-) basal N19, latest Messinian (“Lago Mare” phase), latest Kapitean or earliest Opoitian, latest Miocene.4.Zone IV, SR32–SR 18, warm to very warm, 4.8–±2.7 m.y., within Lower Gilbert — within Upperg Gauss, N19 within N21, Zanclean-Piacenzian, Opoitian Pliocene.5.Zone V, SR17–SR 12, cool, ±2.7 m.y.—age of top unknown, Upper Gauss-Lower Matuyama, within N21 (−N22?), Santernian or basal Calabrian s.l., Waipipian, basal Pleistocene (Late Pliocene of workers with different Pliocene-Pleistocene boundary concepts).

Late Neogene planktonic foraminiferal biostratigraphy and climatostratigraphy of the Solo River section (Java, Indonesia)

Paleoclimate changes are reconstructed from Late Miocene-earliest Pleistocene deep-water sediments of the Solo River section, using fluctuations in planktonic foraminiferal faunas, water depth and clastic influx. Intervals with common cold-water planktonics ( Globigerina bulloides, Neogloboquadrina cf. pachyderma) are thought to reflect periods of increased upwelling, triggered by Antarctic glaciations. Correlations with well Bodjonegoro-1 (Java), DSDP Site 62-1 and Lamont Core RC 12–66 (Equatorial Pacific) using planktonic foraminiferal datum levels and paleoclimate trends suggest non-synchroneity of several commonly used datums, probably due to differences in species concepts. It also allowed dating of the climate changes with regard to the magnetostratigraphic and numerical time scales. For correlations between different faunal provinces global climate changes are an extremely useful tool, probably superior to any single faunal datum. Using this, with other evidence, the following correlations could be obtained between the five “climatostratigraphic” zones in the Solo River section and the Mediterranean and New Zealand stages (from bottom to top): 1. Zone I, samples SR 63–SR 53, cool, older than 6.0 m.y. – ±5.8 m.y., magnetostratigraphic Epoch 6 (and older?) — basal Epoch 5, planktonic zone (Upper N16?-) N17, Mediterranean stages (upper?) Tortonian—Early Messinian, New Zealand Stages Tongaporutuan—Early Kapitean, Late Miocene. 2. Zone II, SR 52–SR 35, moderately warm with fluctuations, ± 5.8 m.y.–5.0 m.y., Epoch—lowermost Gilbert, upper N17 (−N18?), Late Messinian (evaporite phase), Late Kapitean, Late Miocene. 3. Zone III, SR 34–SR 33, cool, 5.0–4.8 m.y., within Lower Gilbert, (N18?-) basal N19, latest Messinian (“Lago Mare” phase), latest Kapitean or earliest Opoitian, latest Miocene. 4. Zone IV, SR32–SR 18, warm to very warm, 4.8–±2.7 m.y., within Lower Gilbert — within Upperg Gauss, N19 within N21, Zanclean-Piacenzian, Opoitian Pliocene. 5. Zone V, SR17–SR 12, cool, ±2.7 m.y.—age of top unknown, Upper Gauss-Lower Matuyama, within N21 (−N22?), Santernian or basal Calabrian s.l., Waipipian, basal Pleistocene (Late Pliocene of workers with different Pliocene-Pleistocene boundary concepts).

Recent, Supracrustal, Carbonate Cementation, Florida Keys: ABSTRACT

Algal stromatolites, the crust of which ranges in age from 5,680 years B.P. at the bottom to 400 years B.P. at the top, overlie Pleistocene bedrock in the Florida Keys. Recent beachrock has been reported at Dry Tortugas, and recent cay rock was discovered at Bahia Honda. Two examples of supracrustal carbonate cementation were found in the intertidal zone of the Florida Keys. On the Florida Bay side of Grassy Key, small gastropod shells of the genera Cerithium and Batillaria are cemented to the top surface of the laminated crust that overlies the Pleistocene Key Largo Limestone. On the Atlantic side of Missouri Key, isolated blocks of rubble are cemented to the top of the crust. Preliminary observations of thin sections suggest that the low-magnesium calcite cement includes alteration products of the underlying crust as well as supracrustal clasts at both Grassy End_Page 908------------------------------ Key and Missouri Key. The top of the crust has been dated at approximately 400 years B.P., indicating very recent cementation in the littoral zone of these areas. End_of_Article - Last_Page 909------------

Pleistocene Patch Reefs and Holocene Swamp Morphology, Grand Cayman Island, West Indies

Patterns of mangrove and non-mangrove species mosaics within the mangrove swamps of Salt Creek, Grand Cayman Island, West Indies, are related to substrate topography and geology. Non-mangrove vegetation is localized on emergent 'dry cays' within the swamp. Both lithological and palaeontological evidence suggests that these bedrock protrusions may be interpreted as a series of Pleistocene patch reefs which were initially slightly elevated above a sandy and silty lagoon floor. The Pleistocene bedrock is overlain by a laminated crust of subaerial origin, above which are Holocene sediments. The Holocene sediments consist of a localized basal orange mud and an overlying cover of mangrove- derived peat. This sequence from subaerial to intertidal sediments records the Holocene marine transgression of the area. Pleistocene patch reefs are at present emergent features, but would be submerged and covered by sediments if the transgression were to continue. It is suggested that this situation is equivalent to an early stage in a similar transgression already identified on the submerged coastal shelf of Belize, central America.

Mixing Zone Dolomite in Tidal-Flat Sediments of Central-West Andros Island, Bahamas: ABSTRACT

The central-west coast of Andros Island is a complex carbonate facies mosaic, deposited at or near mean sea level. The shore has prograded intermittently during the past 3,000 years to produce a seaward-thickening wedge of sediments up to 25 km wide and about 4 m thick beneath the present shoreline. Old channel levees and beach ridges have been preserved during progradation as topographically high ridges which allow the development of freshwater lenses beneath. These lenses show considerable seasonal variation, both in geometry and pore-water chemistry. Mixing zones, extending laterally a few hundred meters around the lenses and down to Pleistocene bedrock, separate the fresh waters of the lenses (with high alkalinity and low ionic concentration), from adjacent saline and hypersaline waters (with low alkalinity and high ionic concentration). Fresh waters are generally undersaturated with aragonite, calcite, and dolomite, but calcite saturation may occur locally. The ends of aragonite needles, skeletal grains, and pellets are commonly corroded, although low-magnesian calcite crystals may locally enclose and replace aragonite by dissolution-reprecipitation. Water in the mixing zone, between 2,500 and 15,000 ppm Cl-, is undersaturated with respect to aragonite and low-magnesian calcite, but supersaturated with respect to calcium magnesium carbonates. X-ray diffraction (XRD) studies indicate small amounts of (< 6%) of protodolomite (38 to 44 mole % of MgCO3) distributed in patches across whichever sedimentary facies are intersected by the mixing zone. The mixing-zone origin of the protodolomite is however equivocal, as similar compositions occur more rarely with saline pore waters not associated with present or past mixing zones. SEM reveals 1µm euhedral rhombic protodolomite crystals between and engulfing aragonite needles. The needles may later dissolve. Chemical data from mixing zones indicate precipitation of a magnesium-rich phase frequently in excess of observed protodolomite concentrations; a huntite phase is indicated by considerations of stability, but is unsupported by XRD results. End_of_Article - Last_Page 457------------

Pleistocene biostratigraphy, chronostratigraphy and paleocirculation of the southeast pacific central water core RC 11-220

An 11-m core, RC 11-220, raised from a depth of 2,950 m in the unstudied Southeast Pacific Central Water of the Tuamotu Ridge (14° 49′S 139° 58′W) received paleontologic and paleoecologic analysis. Eight biostratigraphic horizons were recognized (6 planktonic foraminiferal, 1 coccolithophorid and the discoaster extinction) defining the core as continuous through the basal Pleistocene. The Globorotalia truncatulinoides (d'Orbigny) datum was approached but not encountered. The core has an estimated average sedimentation rate of 0.60 cm/10 3 years. Extrapolation from two paleomagnetic datums (Brunhes/Matuyama, ca. 0.69 Ma and the top of the Olduvai, ca. 1.61 Ma) indicates the age of the core bottom to be ca. 1.87 Ma. Based on the evidence recorded in RC 11-220 and our knowledge of the circulation patterns at the core site today, the following paleocirculation model is proposed. The total carbonate and coarse fraction data indicate a relatively constant depositional pattern and productivity. In addition, judging from the faunal dominance and the distributional pattern of key species such as Globigerinoides ruber (d'Orbigny), Globigerinoides sacculifer (Brady) and Globigerinita glutinata (Egger), a minor shift in the salinity regime is suggested while temperature remained relatively constant. On the average, salinity was slightly higher during the first approximate million years and was somewhat reduced during the last million years B.P. The major conclusion of this study however is that the character of the surface South Central Pacific Waters remained relatively constant throughout the Pleistocene.

Aspects of Sedimentation and Development of a Carbonate Bank in the Barracuda Keys, South Florida

ABSTRACT An extensive carbonate bank in the Barracuda Keys, Florida, was studied to ascertain those factors influencing its growth and present configuration. Five hydrodynamically or biologically controlled sedimentary subenvironments were distinguished: tidal channels, unstable banks, stable banks (including bare-sand, Thalassia, and mangrove island) and silty lagoons. The bank is a closed system wherein local biological production of sediment is in equilibrium with physical dispersal of sediment. Small amounts of fine grained sediment are derived from the Gulf of Mexico, but this material is insignificant relative to continued bank development. Sediment is generally of uniform size, and responds to current flow more as unit sheets than as individual particles, thereby permitting a maximum amount of sediment transport. The major constructional process is the flood tide current, which transports sediment by traction, saltation, and to a lesser extent, suspension and flotation. Steady southeasterly wind-waves cause cross-bank transportation but are subordinate to tides as an agent of bank construction. The basin-shaped Pleistocene bedrock surface exerted principal control on localization of the overlying bank. A resistant limestone ridge on the northern margin of the study area is a barrier to the dispersal of sediment by waves. Development of this bank may be summarized as follows: preferential accumulation of fine sediment in sink holes, forming coalescing silty banks; contemporaneous colonization of these banks by calcareous algae and marine grasses; entrapment and accumulation of coarse sediment by these marine plants, forming a single, contiguous sand bank; and continued growth by accretion of sediment over avalanche slopes. The bank is probably extending itself into the adjoining lagoon by a process of differential growth. This process is dependent upon stabilization of one part of the bank, while growth continues in another.

Possible Living Analog of the Pleistocene Key Largo Reefs of Florida

Research Article| December 01, 1973 Possible Living Analog of the Pleistocene Key Largo Reefs of Florida J. ROBERT DODD; J. ROBERT DODD 1Department of Geology, Indiana University, Bloomington, Indiana 47401 Search for other works by this author on: GSW Google Scholar DONALD E. HATTIN; DONALD E. HATTIN 1Department of Geology, Indiana University, Bloomington, Indiana 47401 Search for other works by this author on: GSW Google Scholar RICHARD M. LIEBE RICHARD M. LIEBE 2Department of Geology and Earth Science, State University College at Brockport, Brockport, New York 14420 Search for other works by this author on: GSW Google Scholar Author and Article Information J. ROBERT DODD 1Department of Geology, Indiana University, Bloomington, Indiana 47401 DONALD E. HATTIN 1Department of Geology, Indiana University, Bloomington, Indiana 47401 RICHARD M. LIEBE 2Department of Geology and Earth Science, State University College at Brockport, Brockport, New York 14420 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (12): 3995–4000. https://doi.org/10.1130/0016-7606(1973)84<3995:PLAOTP>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation J. ROBERT DODD, DONALD E. HATTIN, RICHARD M. LIEBE; Possible Living Analog of the Pleistocene Key Largo Reefs of Florida. GSA Bulletin 1973;; 84 (12): 3995–4000. doi: https://doi.org/10.1130/0016-7606(1973)84<3995:PLAOTP>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 A living, linear reef about 3.8 km in length has been discovered 0.8 to 1.2 km off Big Pine Key and the Newfound Harbor Keys in the lower Florida Keys. The reef is approximately 60 m wide, lies at depths from 4.5 to 7 m, and is growing on, and slightly landward of, a slope where Pleistocene bedrock rises with relative abruptness. A deeper, flat area on the seaward side of the reef is, in most places, a Thalassia-Cymodocea (sea grasses) meadow which is usually separated from the reef by a narrow, barren belt of fine-grained sediment. The outer portion of the reef consists of small, scattered coral heads and octocorals separated by a patchy veneer of sediment. The main body of the reef includes large, commonly coalescent coral heads, some standing at least 2.5 m above the sea floor. Next landward is a zone of smaller coral heads and abundant octocorals, followed by an area of large heads of Montastrea annularis. The previously known patch reefs off the Newfound Harbor Keys lie farther landward in shallower water. Although the sediment veneer is thin across much of the linear reef, accumulations of skeletal sand and gravel up to 50 cm thick, are common in areas of greatest coral growth. Geometry and biota of this reef, as well as its location subparallel to the present shoreline, suggest that the reef may be a living analog of at least a part of the Pleistocene Key Largo Limestone. 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.

Lithostratigraphic names, upper miocene to lower pleistocene, Northern Aorangi Range, Wairarapa

Abstract Twelve upper Cenozoic lithostratigraphic units at the northern end of the Aorangi Range are formally defined and their stratigraphic and interfacies relationships are illustrated and discussed. In order of increasing age they are: Pukenui Limestone (Lower Pleistocene); Onoke Group (uppermost Miocene, Pliocene, and basal Pleistocene) containing two main facies, (1) shallow-water bioclastic and chemical facies comprising Bull Creek Limestone, Haurangi Limestone, Makara Greensand, and Clay Creek Limestone, and (2) shallow- to deep-water inorganic clastic facies comprising Greycliffs Formation and Mangaopari Mudstone with Bridge Sandstone Member; Palliser Group (Upper Miocene) containing Bells Creek Mudstone and Sunnyside Conglomerate. All except Onoke Group and Bells Creek Mudstone are new names. Biostratigraphic zones represented in each formation and probable correlations with stages are mentioned but not exhaustively discussed.

Recent Carbonate Sedimentation by Tidal Channels in the Lower Florida Keys

ABSTRACT Bluefish Channel, north of Key West, Florida, is a prominent ebb channel incised into a thick Recent carbonate bank that overlies Pleistocene limestone. The dominant sediments are Halimeda, foraminifera, molluscs and fragments derived from the Pleistocene bedrock. In as much as the source area lies along the entire course of the channel, sediment mixing results in textural inversions (abnormal size-to-roundness relations) and characteristically negatively-skewed channel sands. A plot of sorting versus grain size of various energy-level sediments studied, reveals a sinusoidal trend similar to that of Folk and Robles (1964) for the beach environment. The lower deflections of the sinusoidal curve coincide with the best sorted sediments of the study area. With increased sorting and abrasion, the constituents tend to be distributed proportionally in the sediment. The best sorted sediment is mature medium calcarenite, a mixture of four constituents in almost equal proportions. Some calcarenites deposited at the tidal delta, adjacent to the channel, show the initial stages of penecontemporaneous, submarine cementorion by chemically precipitated aragonite crystals. This process of cementation is qualitatively similar to the formation of Bahamian grapestone as described by Illing (1954). Hydrodynamically, the channel is characterized by the upper-flow regime. The most conspicuous bed forms are straight-crested megaripples at the channel mouth and adjacent parts of the rapidly growing tidal delta. Here beds of cohesive carbonate muds are exposed to submarine erosion, producing armored mud balls and intraformational flat-pebble conglomerates, identical with some of those interpreted as a product of supratidal environment.

Sediments and Fauna of the Rhone Delta, France: ABSTRACT

The Rhone delta is an example of a rapidly growing delta, prograding over a relatively steep slope into the essentially tideless, highly saline Mediterranean. Detailed studies of the sediments and microfaunas by the author and his colleagues have shown that rate of deposition, even more than depth, is the primary factor controlling the nature of the sediments and faunas offshore. Our classification of deltaic-marine environments is accordingly based on rates and depth of deposition. These studies, supplemented by earlier work in the land part of the delta (Kruit, 1955), have provided the basis for the interpretation of 26 core holes drilled to the top of the Pleistocene basement. A clearcut distinction can be made between the onlap complex of coastal-plain sediments formed under conditions of rising sea level during the late Pleistocene--middle Holocene and the offlap delta consisting of marine sediments laid down under conditions of stable sea level since 5,500 B.P. All core holes through the offlap delta reveal a transgressive-regressive sequence. Those sequences with a typical fluviomarine regressive development consist of (in upward direction): 1) a thin slow-deposition basal bryozoa bed; 2) moderate-deposition distal-fluviomarine clays; 3) rapid-deposition proximal-fluviomarine clays and silts; and 4) rapid-deposition fluviomarine-barrier sands. End_of_Article - Last_Page 347------------

Recent Calcium Carbonate Facies of the Great Bahama Bank. 2. Sedimentary Facies

Statistical analysis of the constituent composition and grain-size data accumulated for 218 Bahamian sediment samples resulted in the delineation of the following five facies: (1) coralgal facies-characterized by a relative abundance of skeletal grains, particularly coral and calcareous algae fragments; (2) oölitic facies-characterized by an abundance of oölitically coated grains; (3) grapestone facies-typified by an abundance of grapestone and cryptocrystalline grains; (4) pellet-mud facies-characterized by an abundance of fecal pellets and particles smaller than 1/8 mm.; and (5) mud facies-typified by an abundance of particles smaller than 1/8 mm. and a relative paucity of indurated fecal pellets. The coralgal facies owes its distinctiveness to a relative lack of non-skeletal calcium carbonate precipitation and to the large areas of rock bottom that characterize this depositional environment. In contrast, differences among three of the other four facies are considered to be primarily the product of differential current strength, with current velocities progressively decreasing in intensity from the oölitic to the pellet-mud facies. The contrast between pellet-mud and mud deposits appears to be due largely to a decreased rate of formation and/or induration of fecal pellets in the mud environment. Ideally one might expect Bahamian facies to be distributed in a series of five concentric bands parallel to the bank's margin. The karst surface of the submerged Pleistocene basement rock, however, creates local current conditions that cause the development of a somewhat patchlike facies pattern.

Dolomite in Modern Carbonate Sediments, Southern Florida: ABSTRACT

The western margin of Florida Bay contains extensive shallow-water banks of unconsolidated, fine carbonate mud. The banks are separated by narrow tide channels and rest on hard Pleistocene bedrock. The banks attain a maximum thickness of about 4½ feet. Radiocarbon dates show that they have been formed in the past 4,000 years. The carbonate mud is composed principally of aragonite, with lesser proportions of dolomite and both high- and low-magnesium calcite. The proportion of dolomite varies, ranging up to about 5 per cent by weight of the total carbonate. Other constituents are quartz and opaline sponge spicules, but these rarely form more than 1 or 2 per cent. Dolomite crystals are euhedral rhombohedrons varying in size from less than 1 micron to approximately 60 microns. They commonly have dark internal rhombohedrons that appear to be intergrowths of dolomite and organic materials. Complex clusters of interpenetrating rhombohedrons are present, but are rare. The occurrence of interpenetrating rhombohedrons and intergrowtbs of organic and carbonate material suggests that dolomite has been formed in situ in Florida Bay; however, radiocarbon dating shows that the dolomite is older than 35,000 years and must be detrital. End_of_Article - Last_Page 281------------

Citronelle Age Problem

The Citronelle formation of the Gulf Coast region has been considered, on the evidence of fossil plants, to be late Pliocene in age, but some geologists have thought that it may be basal Pleistocene because of its unconformable relations with the underlying Tertiary formations and its close associations with the overlying Pleistocene formations. In this paper it is shown that the fossil evidence supports no more than a pre-Nebraskan determination, thus making an early Pleistocene correlation as plausible as one of late Pliocene. As a result of the 1948 definition of the Pliocene-Pleistocene boundary by the 18th International Geological Congress, the Pleistocene, in its European type locality, now appears to include a pre-glacial (pre-Gunz, pre-Nebraskan) section, the Calabrian-Villafranchian, and possibly part of the Sicilian. Evidence is presented which suggests that equivalent sections in the United States are: Mid-Continent region, Blanco; Atlantic Coast, Citronelle and Sunderland; Gulf Coast, Citronelle and Duck Lake; Pacific Coast, Pedroian and Sierran. In the Gulf Coast region the Citronelle is shown to be the surface equivalent of the basal member of a 3,000-4,000-foot subsurface Pleistocene section. An overlying member of the subsurface section is here named the Duck Lake formation. Succeeding members are correlated with the surface Lissie, Oberlin, and Eunice formations of south Louisiana. These, in turn, are correlated with the glacial Pleistocene deposits, Aftonian, Yarmouth, and Sangamon.

Late Cenozoic Marine Glacial Sediments and Marine Terraces of Middleton Island, Alaska

Middleton Island, lying near the margin of the continental shelf in the Gulf ot Alaska, is about 5 miles long, 1 mile wide, and 126 feet in maximum elevation. A Pliocene or Pleistocene bedrock sequence, totaling 3,675 feet in thickness and consisting chiefly of marine glacial sediments, is exposed on and near the island. The bedrock sequence strikes N. 27°-55° E. and dips 22°-30° NW. Pulsating emergence of the island in late Pleistocene (?) and Recent time is recorded by uplifted marine terraces at five levels between 10 and 105 feet above the present sea-level. The deposits of gravel, sand, and mud overlying the wave-cut bedrock surfaces of the terraces are largely, if not entirely, residual material derived from the bedrock.

Villafranchian Stratigraphy in Southern and Southwestern Europe

The deposits containing the classic Villafranchian fauna in Italy (Po Valley, upper and lower Arno Valley, and elsewhere in the peninsula), the Saône Valley of eastern France, and the Puy-en-Velay Basin (Haute-Loire) of central France not only consistently overlie sediments laid down during Upper Pliocene times but also are, in turn, immediately overlain by deposits that clearly belong to the first interglacial (Cromer Forest-Bed-Saint Prestian) stage. With the exception of peninsular Italy, where a marine regime still prevailed, the beds in question, of continental facies and belonging to a Villafranchian stage, represent a comparatively sudden break in the long sedimentary cycle that had prevailed in southern and southwestern Europe throughout Middle and Upper Pliocene (Plaisancian-Astian) times. During the Villafranchian stage, a marked lowering of the temperature occurred, supporting the view that the deposits laid down at this time were accumulated under conditions of glaciation in northern Europe, the Alps, and the Pyrenees. Furthermore, immediately prior to this phase of climatic change, a series of orogenic movements, apparently connected with a time of marine regression, profoundly modified the entire Apennine region. On the basis of these facts, the Villafranchian stage should not be retained in the Pliocene but should be considered basal Pleistocene.

Balcones, Luling, and Mexia Fault Zones in Texas

The Balcones fault zone crosses the San Marcos arch and is located between the comparatively flat dip of the Edwards Plateau and the more steeply dipping beds of the Coastal Plain. It is composed principally of faults with downthrown side on the southeast. The throw on faults of this zone approximates 1,200 feet in northwestern Bexar County. The Luling fault zone lies coastward from the Balcones fault zone and is composed principally of faults with downthrown side on the northwest. In Caldwell County along San Marcos River a total throw of more than 1,500 feet is indicated by faults of the Luling type. The Mexia fault zone lies eastward and southeastward from the Luling zone and is characterized by faults with downthrown side on the southeast and by faults with downthrown side on the northwest. Both commonly occur with a graben of varying width between them. This zone of faults extends from north and northeast of Mexia, Limestone County, southwest through parts of Milam Burleson, Lee, Bastrop, Fayette, Gonzales, and probably through parts of De Witt, Karnes, Goliad, Bee, Live Oak, and Duval counties. Major movement along these faults probably occurred in late Catahoula or early Oakville (Miocene) time, thus affecting sedimentation of this period. Minor faults are present in Pliocene and basal Pleistocene formations. Some Recent movement is recorded.