DualBoot Backtrack 5r3 iso sur pc windows 8.1 x64 avec bios UEFI - Forum - Linux / Unix Combien de ram pour Backtrack 5 r3? Dropshare 5 1 16. - Forum - Linux / Unix. The Basics Chapter 1-3 Starting BACKTRACK 1 Click the Start button on the Windows taskbar and move the cursor up the list to Programs. Select the BACKTRACK 5 program group (or whatever name you gave to the program group when you installed it) and then select BACKTRACK 5.X to start the program. 2 The first time you open BACKTRACK you will be.
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- Running backtrack
- Backtrack output
- Oceanic and continental tectonic subsidence
The
backtrack
module is used to find paleo water depths from a tectonic subsidence model, and sediment decompaction over time.The tectonic subsidence model is either an age-to-depth curve (in ocean basins) or rifting (near continental passive margins).You can either run
backtrack
as a built-in script, specifying parameters as command-line options (..
):…or
importpybacktrack
into your own script, calling its functions and specifying parameters as function arguments (..
):Note
You can run
python-mpybacktrack.backtrack_cli--help
to see a description of all command-line options available, orsee the backtracking reference section for documentation on the function parameters.For example, revisiting our backtracking example, we can run it from the command-line as:
…or write some Python code to do the same thing:
Note
The drill site file
pybacktrack_examples/test_data/ODP-114-699-Lithology.txt
is part of the example data.For each stratigraphic layer in the input drill site file,
backtrack
can write one or more parameters to an output file.Running the above example on ODP drill site 699:
…produces an amended drill site output file containing an extra base sediment layer,and a decompacted output file containing the decompacted output parameters likesediment thickness and water depth.
The amended drill site output file:
There is an extra base sediment layer that extends from the bottomof the drill site (516.3 metres) to the total sediment thickness (601 metres).The bottom age of this new base layer (86.79 Ma) is the age of oceanic crust that ODP drill site 699 is on.If it had been on continental crust (near a passive margin such as DSDP drill site 327) thenthe bottom age of this new base layer would have been when rifting started(since we would have assumed deposition began when continental stretching began).
Jixipix moku hanga 1 45 mph. See also
Base sediment layer and Oceanic versus continental drill sites
The decompacted output file:
The age, compacted_depth and lithology columns are the same as the bottom_age, bottom_depth and lithology columnsin the input drill site (except there is also a row associated with the surface age).
The compacted_thickness column is the total sediment thickness (601 metres - see base sediment layer ofamended drill site above) minus compacted_depth.The decompacted_thickness column is the thickness of all sediment at the associated age. In other words, at each consecutive ageanother stratigraphic layer is essentially removed, allowing the underlying layers to expand (due to their porosity). At present day(or the surface age) the decompacted thickness is just the compacted thickness. The decompacted_density column is the average densityintegrated over the decompacted thickness of the drill site (each stratigraphic layer contains a mixture of water and sediment accordingto its porosity at the decompacted depth of the layer). The decompacted_sediment_rate column is the rate of sediment deposition in units of metres/Ma.At each time it is calculated as the fully decompacted thickness (ie, using surface porosity only) of the surface stratigraphic layer(whose deposition ends at the specified time) divided by the layer’s deposition time interval. The decompacted_depth column is similar todecompacted_sediment_rate in that the stratigraphic layers are fully decompacted (using surface porosity only) as if no portion of any layer hadever been buried. It is also similar to compacted_depth except all effects of compaction have been removed.The dynamic_topography column is the dynamic topography elevation relative to present day (or zero if no dynamic topography model was specified).
Finally, tectonic_subsidence is the output of the underlying tectonic subsidence model,and water_depth is obtained from tectonic subsidence by subtracting an isostatic correction of the decompacted sediment thickness.
Note
The output columns are specified using the
-d
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options), orusing the decompacted_columns argument of the pybacktrack.backtrack_and_write_well()
function.By default, only age and decompacted_thickness are output.A model of the variation of sea level relative to present day can optionally be used when backtracking.This adjusts the isostatic correction of the decompacted sediment thickness to take into account sea-level variations.
There are two built-in sea level models bundled inside
backtrack
:Haq87_SealevelCurve
- The Phanerozoic Record of Global Sea-Level ChangeHaq87_SealevelCurve_Longterm
- Normalised to start at zero at present-day.
A sea-level model is optional. If one is not specified then sea-level variation is assumed to be zero.
Note
A built-in sea-level model can be specified using the
-slm
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options), orusing the sea_level_model argument of the pybacktrack.backtrack_and_write_well()
function.Note
It is also possible to specify your own sea-level model. This can be done by providing your own text file containing a column of ages (Ma) and acorresponding column of sea levels (m), and specifying the name of this file to the
-sl
command-line option or to the sea_level_model argumentof the pybacktrack.backtrack_and_write_well()
function.Tectonic subsidence is modelled separately for ocean basins and continental passive margins.The subsidence model chosen by the
backtrack
module depends on whether the drill site is on oceanic or continental crust.This is determined by an oceanic age grid. Since the age grid captures only oceanic crust, a drill site inside this regionwill automatically use the oceanic subsidence model whereas a drill site outside this region uses the continental subsidence model.The default present-day age grid bundled inside
backtrack
is a6-minute resolution grid of the age of the world’s ocean crust:- Müller, R.D., Seton, M., Zahirovic, S., Williams, S.E., Matthews, K.J., Wright, N.M., Shephard, G.E., Maloney, K.T., Barnett-Moore, N., Hosseinpour, M., Bower, D.J. & Cannon, J. 2016,Ocean Basin Evolution and Global-Scale Plate Reorganization Events Since Pangea Breakup,Annual Review of Earth and Planetary Sciences, vol. 44, pp. 107 .DOI: 10.1146/annurev-earth-060115-012211
Note
You can optionally specify your own age grid using the
-a
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options), orusing the age_grid_filename argument of the pybacktrack.backtrack_and_write_well()
function.ODP drill site 699 is located on deeper ocean crust (as opposed to shallower continental crust):
So it will use the oceanic subsidence model.
See also
In contrast, DSDP drill site 327 is located on shallower continental crust (as opposed to deeper ocean crust):
So it will use the continental subsidence model. Since continental subsidence involves rifting, it requires a rift start and end time.These extra rift parameters can be specified at the top of the drill site file as
RiftStartAge
and RiftEndAge
attributes(see Continental subsidence).See also
![1en1is3 Backtrack dl1 - YouTube 1en1is3 Backtrack dl1 - YouTube](https://www.macsoftdownload.com/wp-content/uploads/2019/09/Backtrack-Mac.png)
If you are not sure whether your drill site lies on oceanic or continental crust then first prepare your drill site assuming it’s onoceanic crust (since this does not need rift start and end ages). If an error message is generated whenrunning backtrack then you’ll need to determine the rift start and end age, thenadd these to your drill site file as
RiftStartAge
and RiftEndAge
attributes, and then run backtrack again.The tectonic subsidence at present day is used in both the oceanic and continental subsidence models.Tectonic subsidence is unloaded water depth, that is with sediment removed.So to obtain an accurate value,
backtrack
starts with a bathymetry grid to obtain the present-day water depth (the depth of the sediment surface).Then an isostatic correction of the present-day sediment thickness (at the drill site) takes into account the removal of sediment to revealthe present-day tectonic subsidence. The isostatic correction uses the average sediment density of the drill site stratigraphy.The default present-day bathymetry grid bundled inside
backtrack
is a6-minute resolution global grid of the land topography and ocean bathymetry (although only the ocean bathymetry is actually needed):- Amante, C. and B. W. Eakins, ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis.NOAA Technical Memorandum NESDIS NGDC-24, 19 pp, March 2009
Note
You can optionally specify your own bathymetry grid using the
-t
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options), orusing the topography_filename argument of the pybacktrack.backtrack_and_write_well()
function.Note
If you specify your own bathymetry grid, ensure that its ocean water depths are negative.It is assumed that elevations in the grid above/below sea level are positive/negative.
Oceanic subsidence is somewhat simpler and more accurately modelled than continental subsidence (due to no Drama prototyping animation & design tool 2 0 3. lithospheric stretching).
The age of oceanic crust at the drill site (sampled from the oceanic age grid) can be converted to tectonic subsidence (depth with sediment removed)by using an age-to-depth model. There are two models built into
backtrack
:GDH1
- Stein and Stein (1992) Model for the global variation in oceanic depth and heat flow with lithospheric ageCROSBY_2007
- Crosby et al. (2006) The relationship between depth, age and gravity in the oceans
The default model is
GDH1
.Note
These oceanic subsidence models can be specified using the
-m
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options), orusing the ocean_age_to_depth_model argument of the pybacktrack.backtrack_and_write_well()
function.Note
It is also possible to specify your own age-to-depth model. This can be done by providing your own text file containing a column of ages and acorresponding column of depths, and specifying the name of this file along with two integers representing the age and depth column indices to the
-m
command-line option. Or you can pass your own function as the ocean_age_to_depth_model argument of the pybacktrack.backtrack_and_write_well()
function,where your function should accept a single age (Ma) argument and return the corresponding depth (m).Backtrack 1986
Since the drill site might be located on anomalously thick or thin ocean crust, a constant offset is added to the age-to-depth model to ensure the model subsidence matchesthe actual subsidence at present day.
Continental subsidence is somewhat more complex and less accurately modelled than oceanic subsidence (due to lithospheric stretching).
The continental subsidence model has two components of rifting as described inPyBacktrack 1.0: A Tool for Reconstructing Paleobathymetry on Oceanic and Continental Crust.The first contribution is initial subsidence due to lithospheric thinning where low-density crust is thinned and hot asthenosphere rises underneath.In our model the crust and lithospheric mantle are identically stretched (uniform extension).The second contribution is thermal subsidence where the lithosphere thickens as it cools due to conductive heat loss.In our model thermal subsidence only takes place once the stretching stage has ended.In this way, there is instantaneous stretching from a thermal perspective (in the sense that, although stretching happens over a finite period of time,the model assumes no cooling during the stretching stage).
Note
The tectonic subsidence at the start of rifting is zero. This is because it is assumed that rifting begins at sea level, and begins with asediment thickness of zero (since sediments are yet to be deposited on newly forming ocean crust).
For drill sites on continental crust, the rift end time must be provided. However the rift start time is optional. If it is not specified thenit is assumed to be equal to the rift end time. In other words, lithospheric stretching is assumed to happen immediately at the rift end time(as opposed to happening over a period of time). This is fine for stratigraphic layers deposited after rifting has ended, since the subsidence will bethe same regardless of whether a rift start time was specified or not.
Note
The rift start and end times can be specified in the drill site file using the
RiftStartAge
and RiftEndAge
attributes.Or they can be specified directly on the backtrack
command-line using the -rs
and -re
options respectively(run python-mpybacktrack.backtrack_cli--help
to see all options). Or using the rifting_period argumentof the pybacktrack.backtrack_and_write_well()
function.If a rift start time is specified, then the stretching factor varies exponentially between the rift start and end times (assuming a constant strain rate).The stretching factor at the rift start time is
1.0
(since the lithosphere has not yet stretched). The stretching factor at the rift end time isestimated such that our model produces a subsidence matching the actual subsidence at present day, whilealso thinning the crust to match the actual crustal thickness at present day.Note
The crustal thickness at the end of rifting and at present day are assumed to be the same.
Warning
If the estimated rift stretching factor (at the rift end time) results in a tectonic subsidence inaccuracy(at present day) of more than 100 metres, then a warning is emitted to
standarderror
on the console.This can happen if the actual present-day subsidence is quite deep and the stretching factor required to achievethis subsidence would be unrealistically large and result in a pre-rift crustal thickness(equal to the stretching factor multiplied by the actual present-day crustal thickness) that exceedstypical lithospheric thicknesses (125km). In this case the stretching factor is clamped to avoid this but,as a result, the modeled subsidence is not as deep as the actual subsidence.The default present-day crustal thickness grid bundled inside
backtrack
is a1-degree resolution grid of the thickness of the crustal part of the lithosphere:- Laske, G., Masters., G., Ma, Z. and Pasyanos, M., Update on CRUST1.0 - A 1-degree Global Model of Earth’s Crust,Geophys. Res. Abstracts, 15, Abstract EGU2013-2658, 2013
Note
You can optionally specify your own crustal thickness grid using the
-k
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options), orusing the crustal_thickness_filename argument of the pybacktrack.backtrack_and_write_well()
function.The effects of dynamic topography can be included in the models of tectonic subsidence (both oceanic and continental).
A dynamic topography model is optional. If one is not specified then dynamic topography is assumed to be zero.
All dynamic topography models consist of a sequence of time-dependent global grids (where each grid is associated with a past geological time).The grids are in the mantle reference frame (instead of the plate reference frame) and hence the drill site location must be reconstructed(back in time) before sampling these grids. To enable this, a dynamic topography model also includes an associated static-polygonsfile to assign a reconstruction plate ID to the drill site, and associated rotation file(s) to reconstruct the drill site location.
Warning
If the drill site is reconstructed to a time that is older than the age of the crust it is located on, then a warning is emitted(to
standarderror
on the console) stating that the dynamic topography model does not cover, or cannot interpolate, the drill site location.This is because it does not make sense to reconstruct a parcel of crust prior to the time at which that parcel appeared.This can happen when interpolating between the two dynamic topography grids that surround the reconstruction time because the older of the two gridscould be arbitrarily old. In this case the younger of the two grids is sampled.This same warning is also emitted if the dynamic topography model does not go back far enough in time.In this case the oldest dynamic topography grid in the model is sampled.Backtrack 1.0.1 - PyPI
Dynamic topography is included in the oceanic subsidence model by adjusting the subsidence to account for the change indynamic topography at the drill site since present day.
Backtrack 1 360
Dynamic topography is included in the continental subsidence model by first removing the effects of dynamic topography (between the start of rifting and present day)prior to estimating the rift stretching factor. This is because estimation of the stretching factor only considers subsidence due to lithospheric thinning (stretching)and subsequent thickening (thermal cooling). Once the optimal stretching factor has been estimated, the continental subsidence is adjusted to account for the change indynamic topography since the start of rifting.
See also
These are the built-in dynamic topography models bundled inside
backtrack
:- Müller et al., 2017 - Dynamic topography of passive continental margins and their hinterlands since the Cretaceous
- Rubey et al., 2017 - Global patterns of Earth’s dynamic topography since the Jurassic
- Müller et al., 2008 - Long-term sea-level fluctuations driven by ocean basin dynamics
Note
The above model links reference dynamic topography models that can be visualized in the GPlates Web Portal.
The
M1
model is a combined forward/reverse geodynamic model, while models M2
-M7
are forward models.Models ngrand
, s20rts
and smean
are backward-advection models.The backward-advection models are generally good for the recent geological past (up to last 70 million years).While the M1
-M7
models are most useful when it is necessary to look at times older than 70 Mabecause their oceanic paleo-depths lack the regional detail at more recent times that the backward-advection models capture(because of their assimilation of seismic tomography).M1
also assimilates seismic tomography but suffers from other shortcomings.Note
A built-in dynamic topography model can be specified using the
-ym
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options), orusing the dynamic_topography_model argument of the pybacktrack.backtrack_and_write_well()
function.Note
Backtrack 1 3.0
It is also possible to specify your own dynamic topography model.This can be done by providing your own grid list text file with the first column containing a list of the dynamic topography grid filenames(where each filename should be relative to the directory on the list file) and the second column containing the associated grid times (in Ma).You’ll also need the associated static-polygons file, and one or more associated rotation files.The grid list filename, static-polygons filename and one or more rotation filenames are then specified using the
-y
command-line option (run python-mpybacktrack.backtrack_cli--help
to see all options),or to the dynamic_topography_model argument of the pybacktrack.backtrack_and_write_well()
function.