Outcrop

About: Outcrop is a research topic. Over the lifetime, 4852 publications have been published within this topic receiving 83232 citations. The topic is also known as: rocky outcrop.

Mesozoic and Cenozoic Chronostratigraphy and Cycles of Sea-Level Change

Abstract: Sequence-stratigraphic concepts are used to identify genetically related strata and their bounding regional unconformities, or their correlative conformities, in seismic, well-log, and outcrop data. Documentation and age dating of these features in marine outcrops in different parts of the world have led to a new generation of Mesozoic and Cenozoic sea-level cycle charts with greater event resolution than that obtainable from seismic data alone. The cycles of sea-level change, interpreted from the rock record, are tied to an integrated chronostratigraphy that combines state-of-the-art geochronologic, magnetostratigraphic and biostratigraphic data. In this article we discuss the reasoning behind integrated chronostratigraphy and list the sources of data used to establish this framework. Once this framework has been constructed, the depositional sequences from sections around the world, interpreted as having been formed in response to sea-level fluctuations, can be tied into the chronostratigraphy. Four cycle charts summarizing the chronostratigraphy, coastal-onlap patterns, and sea-level curves for the Cenozoic, Cretaceous, Jurassic, and Triassic are presented. A large-scale composite-cycle chart for the Mesozoic and Cenozoic is also included (in pocket). The relative magnitudes of sea-level falls, interpreted from sequence boundaries, are classified as major, medium, and minor, as are the condensed sections associated with the intervals of sediment starvation on the shelf and slope during the phase of maximum shelf flooding during each cycle. Generally, only the sequence boundaries produced by major and some medium-scale sea-level falls can be recognized at the level of seismic stratigraphic resolution; detailed well-log and/or outcrop studies are usually necessary to resolve the minor sequences.

Mesozoic and Cenozoic Sequence Stratigraphy of European Basins

Abstract: The preliminary results of the project, [open quotes]Mesozoic-Cenozoic Sequence Stratigraphy of European Basins[close quotes] (introduced at a seminar in Dijon, France, on May 18-20, 1992), show that the Mesozoic-Cenozoic stratigraphic succession of western Europe can be subdivided into a series of transgressive-regressive facies cycles (second order, 3-50 m.y.) and related to tectonic events by subsidence analysis and regional geology. The distribution of the second-order cycles are shown on a series of transects that extend from the Mediterranean to the North Sea. Where possible, each transgressive-regressive phase has been subdivided into a series of higher frequency sequence cycles (third order, 0.5-3 m.y.). These sequence cycles are identified in regions with good outcrops and biostratigraphic control. The sequence stratigraphy interpretation of these outcrop sections provides documentation for the age and distribution of the second- and third-order stratigraphic cycles of western Europe. Subsurface seismic and well data from the North Sea Basin, Paris basin, and the Mediterranean area are interpreted in terms of sequence stratigraphy and correlated to the outcrop reference sections. Chronobiostratigraphy and numerical ages are based on a series of new charts made especially for this project that show the latest correlation of the biostratigraphic zones for both microfossils and macrofossilsmore » across Europe. The charts also include a numerical time scale that reconciles the differences between existing time scales.« less

Mesozoic and cenozoic chronostratigraphy and cycles of sea level change

Abstract: Sequence-stratigraphic concepts are used to identify genetically related strata and their bounding regional unconformities, or their correlative conformities, in seismic, well-log, and outcrop data. Documentation and age dating of these features in marine outcrops in different parts of the world have led to a new generation of Mesozoic and Cenozoic sea-level cycle charts with greater event resolution than that obtainable from seismic data alone. The cycles of sea-level change, interpreted from the rock record, are tied to an integrated chronostratigraphy that combines state-of-the-art geochronologic, magnetostratigraphic and biostratigraphic data. In this article we discuss the reasoning behind integrated chronostratigraphy and list the sources of data used to establish this framework. Once this framework has been constructed, the depositional sequences from sections around the world, interpreted as having been formed in response to sea-level fluctuations, can be tied into the chronostratigraphy. Four cycle charts summarizing the chronostratigraphy, coastal-onlap patterns, and sea-level curves for the Cenozoic, Cretaceous, Jurassic, and Triassic are presented. A large-scale composite-cycle chart for the Mesozoic and Cenozoic is also included (in pocket). The relative magnitudes of sea-level falls, interpreted from sequence boundaries, are classified as major, medium, and minor, as are the condensed sections associated with the intervals of sediment starvation on the shelf and slope during the phase of maximum shelf flooding during each cycle. Generally, only the sequence boundaries produced by major and some medium-scale sea-level falls can be recognized at the level of seismic stratigraphic resolution; detailed well-log and/or outcrop studies are usually necessary to resolve the minor sequences.

Understanding Earth’s eroding surface with 10Be

Abstract: For more than a century, geologists have sought to measure the distribution of erosion rates on Earth’s dynamic surface. Since the mid-1980s, measurements of in situ 10Be, a cosmogenic radionuclide, have been used to estimate outcrop and basin-scale erosion rates at 87 sites around the world. Here, we compile, normalize, and compare published 10Be erosion rate data (n = 1599) in order to understand how, on a global scale, geologic erosion rates integrated over 103 to 106 years vary between climate zones, tectonic settings, and different rock types. Drainage basins erode more quickly (mean = 218 m Myr−1; median = 54 m Myr−1) than outcrops (mean = 12 m Myr−1; median = 5.4 m Myr−1), likely reflecting the acceleration of rock weathering rates under soil. Drainage basin and outcrop erosion rates both vary by climate zone, rock type, and tectonic setting. On the global scale, environmental parameters (latitude, elevation, relief, mean annual precipitation and temperature, seismicity, basin slope and area, and percent basin cover by vegetation) explain erosion rate variation better when they are combined in multiple regression analyses than when considered in bivariate relationships. Drainage basin erosion rates are explained well by considering these environmental parameters (R2 = 0.60); mean basin slope is the most powerful regressor. Outcrop erosion rates are less well explained (R2 = 0.32), and no one parameter dominates. The variance of erosion rates is better explained when subpopulations of the global data are analyzed. While our compilation is global, the grouped spatial distribution of cosmogenic studies introduces a bias that will only be addressed by research in under-sampled regions.

Sedimentary basins formed and carried piggyback on active thrust sheets

Abstract: Small sedimentary basins that formed on the Apennine (southern) margin of the Po basin complex, northern Italy, have been studied using borehole and seismic-reflection information, and their evolution can be dated using the largely marine biostratigraphy of the Miocene to Quaternary sediments. These studies show that the basins formed and were filled while being carried on moving thrust sheets, and they are therefore named piggyback basins. Each of these basins corresponds to the active phase of a different thrust-front ramp. On the Pyrenean (northern) margin of the Ebro basin complex, northern Spain, similar piggyback basins formed between Eocene and mid-Miocene time. They have since been uplifted and eroded and may therefore be studied in outcrop. In northern Spain, much of the basin-fill sediment was deposited in nonmarine environments.