<blockquote>
  <p>No great extinction or burst of diversity separated the Cretaceous
  from the Jurassic Period that had preceded it.</p>
</blockquote>

<p>If there are no strong elements, some key feature are:</p>

<ul>
<li>flower plants</li>
<li>diatoms in the oceans</li>
</ul>

<blockquote>
  <p>Perhaps the most important of these events, at least for terrestrial
  life, was the first appearance of the flowering plants, also called
  the angiosperms or Anthophyta. First appearing in the Lower Cretaceous
  around 125 million years ago, the flowering plants first radiated in
  the middle Cretaceous, about 100 million years ago.</p>
</blockquote>

<p>The <a href="https://ucmp.berkeley.edu/mesozoic/cretaceous/cretaceous.php" rel="nofollow noreferrer">source</a> article also states:</p>

<blockquote>
  <p>Early angiosperms did not develop shrub- or tree-like morphologies,
  but by the close of the Cretaceous, a number of forms had evolved that
  any modern botanist would recognize. The angiosperms thrived in a
  variety of environments such as areas with damper climates, habitats
  favored by cycads and cycadeoids, and riparian zones. High southern
  latitudes were not invaded by angiosperms until the end of the
  Cretaceous. Ferns dominated open, dry and/or low-nutrient lands.
  Typical Jurassic vegetation, including conifers, cycads, and other
  gymnosperms, continued on into the Lower Cretaceous without
  significant changes. At the beginning of this period, conifer
  diversity was fairly low in the higher latitudes of the Northern
  Hemisphere, but by the middle of the period, species diversification
  was increasing exponentially. Swamps were dominated by conifers and
  angiosperm dicots.</p>
</blockquote>

CC BY-SA 4.0
2020-02-16T05:51:02.263Z
2020-02-16T05:51:02.263Z
Stephane Rolland
<p>Short answer, there isn't one. </p>

<p>The J-K boundary does not have a well defined fingerprint or marker, because of this it is in flux with different studies constantly offering to tweek or redefine its date based on their own criteria.  </p>

<p><a href="https://www.sciencedirect.com/science/article/pii/019566719190001S" rel="nofollow noreferrer">https://www.sciencedirect.com/science/article/pii/019566719190001S</a></p>

<p><a href="https://ui.adsabs.harvard.edu/abs/2017EGUGA..1912252L/abstract" rel="nofollow noreferrer">https://ui.adsabs.harvard.edu/abs/2017EGUGA..1912252L/abstract</a></p>

<p><a href="https://www.researchgate.net/publication/236003223_Fixing_a_basal_Berriasian_and_Jurassic-Cretaceous_J-K_boundary-_perhaps_there_is_some_light_at_the_end_of_the_tunnel" rel="nofollow noreferrer">https://www.researchgate.net/publication/236003223_Fixing_a_basal_Berriasian_and_Jurassic-Cretaceous_J-K_boundary-_perhaps_there_is_some_light_at_the_end_of_the_tunnel</a></p>

CC BY-SA 4.0
2020-02-16T02:00:09.317Z
2020-02-16T02:00:09.317Z
John
<ol>
<li>We have one mass extinction that seperates Trias from Jurassic, roughly huge volcanims over a long period of time, and Pangea starting to divide. </li>
<li>Another mass extinction that marks the end of Cretaceous period, linked to the fall of an asteroid.</li>
</ol>

<p>However there is no mass extinction between the two:
What are the crucial elements for defining the limit between Jurassic and Cretaceous?</p>

<geology><paleontology><stratigraphy>
What are the key elements defining the separation between Jurassic and Cretaceous?
Stephane Rolland
# What are the key elements defining the separation between Jurassic and Cretaceous?

(Asked by: username_0 on 2020-02-15)

1. We have one mass extinction that seperates Trias from Jurassic, roughly huge volcanims over a long period of time, and Pangea starting to divide.
2. Another mass extinction that marks the end of Cretaceous period, linked to the fall of an asteroid.

However there is no mass extinction between the two:
What are the crucial elements for defining the limit between Jurassic and Cretaceous?

**Tags:** geology, paleontology, stratigraphy


---

## 2 answers

### Answer by username_1 on 2020-02-16. Score: 3 | Accepted answer

Short answer, there isn't one.

The J-K boundary does not have a well defined fingerprint or marker, because of this it is in flux with different studies constantly offering to tweek or redefine its date based on their own criteria.

<https://www.sciencedirect.com/science/article/pii/019566719190001S>

<https://ui.adsabs.harvard.edu/abs/2017EGUGA..1912252L/abstract>

<https://www.researchgate.net/publication/236003223_Fixing_a_basal_Berriasian_and_Jurassic-Cretaceous_J-K_boundary-_perhaps_there_is_some_light_at_the_end_of_the_tunnel>


---

### Answer by username_0 on 2020-02-16. Score: 1

> No great extinction or burst of diversity separated the Cretaceous
> from the Jurassic Period that had preceded it.

If there are no strong elements, some key feature are:

* flower plants
* diatoms in the oceans

> Perhaps the most important of these events, at least for terrestrial
> life, was the first appearance of the flowering plants, also called
> the angiosperms or Anthophyta. First appearing in the Lower Cretaceous
> around 125 million years ago, the flowering plants first radiated in
> the middle Cretaceous, about 100 million years ago.

The [source](https://ucmp.berkeley.edu/mesozoic/cretaceous/cretaceous.php) article also states:

> Early angiosperms did not develop shrub- or tree-like morphologies,
> but by the close of the Cretaceous, a number of forms had evolved that
> any modern botanist would recognize. The angiosperms thrived in a
> variety of environments such as areas with damper climates, habitats
> favored by cycads and cycadeoids, and riparian zones. High southern
> latitudes were not invaded by angiosperms until the end of the
> Cretaceous. Ferns dominated open, dry and/or low-nutrient lands.
> Typical Jurassic vegetation, including conifers, cycads, and other
> gymnosperms, continued on into the Lower Cretaceous without
> significant changes. At the beginning of this period, conifer
> diversity was fairly low in the higher latitudes of the Northern
> Hemisphere, but by the middle of the period, species diversification
> was increasing exponentially. Swamps were dominated by conifers and
> angiosperm dicots.


---

