User:Leah.I.H./New sandbox

Article Evaluation


 * Article Content
 * The content of the article is all relevant to the subject. However, it skims over the explanations of orbital cycles and does not connect them to cyclostratigraphy through examples or added detail. The information is presented in clear language but does not inform the reader of the science behind cyclostratigraphy. Cyclostratigraphy is explained in a general context, but more detail should be provided. The article links to three other Wikipedia articles for more context: Milankovitch cycles, cyclic sediments, and stratigraphy.
 * Article Tone
 * There is no bias to the article's tone. It gives a very basic definition and general explanation of cyclostratigraphy.
 * Article Sources
 * There are seven sources in the references section, but only two are referenced in the article. It is also worth noting that four of the seven sources are in French.
 * Talk Page Evaluation
 * The Talk Page for this article is empty. This article is rated as "Stub-Class" and is of interest to WikiProject Environment, WikiProject Climate change, and WikiProject Geology.

Article Draft
Cyclostratigraphy is the study of astronomically forced climate cycles within sedimentary successions. It is a subdiscipline of stratigraphy.

Orbital changes
Astronomical cycles, also known as Milankovitch cycles, are variations of the Earth's orbit around the sun due to the gravitational interaction with other masses within the solar system. Due to this cyclicity, solar irradiation varies through time, and these insolation variations influence Earth's climate and the deposition of sedimentary rocks. The main orbital cycles are precession, obliquity, and eccentricity. At present, the main periods are 19 and 23 kyr for precession, 41 kyr and 1.2 Myr for obliquity, and 100 kyr, 405 kyr, and 2.4 Myr for eccentricity.

Applications
Cyclostratigraphic studies of rock records can be used to accurately date events in the geological past, to increase understanding of cause and consequences of Earth's (climate) history, and to constrain depositional mechanisms of sedimentary systems. Stratigraphic indicators of orbital cycles include rock magnetism, geochemistry, biological composition, and physical features like color and facies changes in sediments. To determine the time range of a cyclostratigraphic study, rocks are dated using stratigraphic methods and radiometric dating. Once the time range is calibrated, the rocks are examined for Milankovitch signals and ages are assigned to the sediment layers. The 405-kyr eccentricity cycle can be used to correct chronologies in rocks or sediment cores when variable sedimentation rates make them difficult to assign.

Cyclostratigraphy also aids the study of planetary physics, because it provides information of astronomical cycles that extends beyond 50 Ma (astronomical models are not accurate beyond this). Assigning time ranges to these astronomical cycles can be used to calibrate 40Ar/39Ar dating.

Limitations
Uncertainties can arise when using cyclostratigraphy. Using radioisotope dating to set parameters for time scales introduces a degree of uncertainty. There are also stratigraphic uncertainties, uncertainties due to climate forcing, and uncertainty about Earth's rotational effects on its precession. There is also uncertainty in records extending beyond 50 Ma. Astronomical models are not accurate beyond 50 Ma due to chaos and uncertainties of initial conditions.