Patterns in sediment linked to rain, uplift and sea level change

Date:
July 27, 2020
Source:
University of Texas at Austin
Summary:
In a recent study, researchers show that a natural record -
sediments packed together at basin margins - offers scientists
a powerful tool for understanding the forces that shaped our
planet over millions of years, with implications on present day
understanding.



FULL STORY ========================================================================== Forces that shape the Earth's surface are recorded in a number of natural records, from tree rings to cave formations.


==========================================================================
In a recent study, researchers from The University of Texas at Austin show
that another natural record -- sediments packed together at basin margins
-- offers scientists a powerful tool for understanding the forces that
shaped our planet over millions of years, with implications on present
day understanding The study was published in the journal Geology and
uses a computer model to connect distinct patterns in the sedimentary
deposits to shifts in climate and tectonic activity.

"We are trying to find a way to distinguish the tectonics and the climate signals," said lead author Jinyu Zhang, a research associate at UT's
Bureau of Economic Geology. "By using this numerical model we suddenly
have this power to simulate the world under different tectonics and
climate." Zolta'n Sylvester and Jacob Covault, both research scientists
at the bureau, co-authored the paper.

Geoscientists have long looked to sedimentary basins for clues about
Earth's past climate. That's because sediment supply is closely linked
to environmental factors, such as rainfall or snowfall, that influence
sediment creation through erosion and sediment transport across a
landscape and into a basin. Tectonic factors also influence sediment
creation, with increasing uplift associated with more sediment and
decreasing uplift with less.



========================================================================== However, despite knowledge of sediment supply being linked with climate
and tectonics, the researchers said little is known about how changes
in these phenomena directly influence how sediment is deposited along
basin margins over long time scales.

This study changes that, with Zhang using the open-source computer
program pyBadlands to create a "source-to-sink" 3D model that tracks
how changes in precipitation, tectonic uplift and sea level influence
sediment erosion and deposition. The model uses topography inspired by
the Himalaya Mountains and Indus River Delta to track the sediment as
it makes its way from the mountains, through a river system, and settles
into a basin margin over millions of years.

"This is one of the first [models] to put the landscape evolution part
with the stratigraphic response, depositional response, and do it in 3D," Covault said.

"Jinyu has made a really great step in putting this all together."
The researchers ran 14 different scenarios -- each with a different
climatic, tectonic, and sea level settings -- over a simulated time period
of 30 million years to investigate changes in landscape topography and
sediment deposition.

The different scenarios created distinct patterns in sediment deposition,
which allowed the researchers to draw general conclusions about how
tectonic and climatic factors affect basin margin growth. For example,
changes in uplift take millions of years to affect change in the basin
margin sediments, but once those changes are in effect, they set a new
baseline for behavior. In contrast, changes in precipitation cause much
more abrupt change, followed by a return to the depositional behavior
observed before the climate shift.



==========================================================================
The scenarios showed that sea level could potentially complicate the
delivery of the signal of tectonic change into the basin. For example,
an increase in sea level flooded coastal regions and interfered with
sediment reaching a basin margin. But when this scenario was paired with increased precipitation, the sediment supply was large enough to make
it to the basin margin.

Gary Hampson, a professor at Imperial College London who was not part
of the study, said that the model provides important guidelines for geoscientists looking to reconstruct Earth's past.

"The results increase the confidence with which geoscientists can
interpret tectonic and climatic histories in the geologic archives of
basin margins," he said.

Zhang spent the past two years learning the programming language Python
so he could use the pyBadlands software, which was developed by the
University of Sydney's Tristan Salles.

Sylvester, who leverages similar tools to study erosion and sedimentation
in river systems, said that the computing tools available to geoscientists
are making long-standing yet fundamental questions in geosciences more accessible than ever.

"It's an exciting time," he said. "It's increasingly easier to investigate
the stratigraphic record in a quantitative way."

========================================================================== Story Source: Materials provided by University_of_Texas_at_Austin. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jacob Covault, Zolta'n Sylvester, Jinyu Zhang. How do basin margins
record long-term tectonic and climaticchanges? Geology, 2020;
DOI: 10.1130/G47498.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200727145819.htm

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