The document discusses different types of geological contacts and unconformities: - Geological contacts include normal depositional contacts, intrusive contacts between igneous and older rock, fault contacts where one body has slid past the other, and unconformable contacts where older and younger rock units are parallel but with an irregular surface. - Unconformities result from tectonic uplift or subsidence causing a period of non-deposition. The main types are non-conformities between igneous/metamorphic and overlying sedimentary rock, disconformities where parallel sedimentary layers have an erosional contact plane, and angular unconformities where the layers have different angles. -

1.  Contacts:
• Normal depositional contact.
• Intrusive contact.
• Fault contact.
• Unconformable contact.

2. Contact:
• A surface that separate geological unit
including primary boundaries such as
depositional contact, all kind of
unconformity, intrusive contact, as well as
fault that separate geologic unit.

3. • Normal depositional contact:
• lithogenetic contact at which a
sedimentary or volcanic rock has been
deposite on another rock. The relation
between older and younger rock is
unknown.

5. • Intrusive contact:
• An intrusive contact between younger
igneous rock and an older pre-existing
geological unit into which it has een
intruded.

7. • Fault contact:
• A contact separating two bodies of material
across which one body has slide past the
other.

9. • Unconformable contact:
• The contact in which older and younger
rock unit is parallel to each other but it is
marked by irregular or uneven surface.

11.  Unconformity:
• Introduction.
• Type of unconformity.

12. Unconformity
• It is one of the most common geological
feature found in rocks or in succession.
• It is different then all other geological
structures viz. the fold, joints and faults
• Unconformities are resulted due to tectonic
activity in form of uplift or subsidence of
land
• It is referred to a period of non-deposition

13. Types of Unconformities
• Non-conformity
• When the underlying rocks are
Igneous or Metamorphic (i.e.
unstratified) and the overlying
younger rocks are sedimentary
(stratified) = Non-conformity
• Disconformity
• When the underlying (older)
and overlying (younger)
sedimentary rock strata are
parallel and the contact plane
is an erosional surface=
Disconformity

14. • Angular unconformity
• When the underlying (older)
rocks and overlying (younger)
rock strata show some angle
w.r.t one another=Angular
unconformity

15. Angular unconformity • This sub-area in northern
Chile Showing a geological
angular unconformity: a
contact between layers of
rock at different angles.
• On the right side of the
image, Cretaceous sediments
were tilted upward to an
angle of about 50 degrees,
then eroded. On this surface
volcanic pyroclastic deposits
were deposited as a flat sheet.
• The section of rocks has been
eroding from the east,
exposing the tilted and flat
rock layers.

16.  Shear zone:
• A shear zone is very important structural
disconformity surface in the earth’s crust
and upper mantle. It form as a response to
inhomogenous deformation partitioning
strain into planer or curviplaner high strain
zone .

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